Official USMLE samples – 2013 – BLOCK 1




D – Volume loss (secondary to vomiting in this case) causes hypovolemic
hyponatremia. The body wants to retain fluid and maintain blood pressure, so there is a
compensatory increase in anti-diuretic hormone (ADH/vasopressin).


E – Xanthogranulomatous pyelonephritis (XGP) is a rare form of chronic pyelonephritis, especially associated with
Proteus infection. Tumor-like growth, upper urinary tract infection, and (this is key) lipid-laden foamy macrophages make
this neither acute pyelo nor cancer. Malacoplakia causes GU papules/ulcers, typically of the bladder (not super important).


E – Wernicke–Korsakoff syndrome causes degeneration of the mammillary bodies (important fact).
Korsakoff’s Syndrome on the boards invariably includes anterograde amnesia with confabulation (making things up).

Anterograde amnesia is a loss of the ability to create new memories after the event that caused the amnesia, leading to a
partial or complete inability to recall the recent past, while long-term memories from before the event remain intact.


E – A chronic “heaped up” ulcerative lesion of the skin, especially on sun-exposed areas in people who spend time
outdoors, means cancer. If it’s keratinocytes at play (and not melanocytes), that leaves you with either squamous
cell or basal cell carcinoma.


A – Gram positive cocci in pairs and chains means streptococcus. Group B streptococcus can be part of the flora of
the mother’s vagina (which babies are exposed to during vaginal birth). It’s the most important cause of neonatal sepsis and meningitis.


A – Naughty alcohols–methanol (wood alcohol), ethylene glycol (antifreeze), and isopropyl alcohol (rubbing alcohol)–cause
terrible damage through their metabolites (formic acid, oxalic acid, and acetone, respectively). The trick in treatment is to prevent the conversion
of the original alcohols into their toxic metabolites. This can be done by saturating the alcohol dehydrogenase enzyme with intravenous alcohol or
through the use of fomepizole (a competitive inhibitor).


Genital warts (or condylomata acuminata, venereal warts, anal warts and anogenital warts) are symptoms of a highly contagious sexually transmitted disease caused by some types of human papillomavirus (HPV).

D – HPV (particularly strains 16 and 18) causes squamous cell carcinoma of the cervix. Thankfully, there’s a vaccine for that now.


B – You don’t necessarily have to know a ton clinically about differentiating endemic fungal diseases, but you do have to know
which areas they come from and what they look like. Coccidiomycosis comes from the southwest (i.e. California). Histoplasmosis
is endemic to Ohio River valley. Blastomycosis on the east coast. Paracoccidioidomycosis from Mexico and South America.


B – Esophageal varices are a big deal and can be fatal. The left gastric vein is to blame. Periumbilical varices can cause caput medusa.
Superior rectal varices cause internal hemorrhoids.

In medicine (gastroenterology), esophageal varices (or oesophageal varices) are extremely dilated sub-mucosal veins in the lower third of the esophagus. They are most often a consequence of portal hypertension, commonly due to cirrhosis; patients with esophageal varices have a strong tendency to develop bleeding.

Caput medusae, also known as palm tree sign, is the appearance of distended and engorged superficial epigastric veins, which are seen radiating from the umbilicus across the abdomen.

Image result for Esophageal varicesImage result for gastric vein

Image result for Periumbilical varicesImage result for Periumbilical varicesImage result for Periumbilical varices


D – Antibiotic-associated diarrhea caused by clostridium difficile can be tenacious, difficult to treat, and even fatal.
Alcohol-based rubs are not sufficient to kill the spores. Handwashing with soap is necessary, and equipment should be autoclaved to clean it.



C – Lymphatic spread of disease moves through lymphatic channels from distal to proximal. Just follow logic.
In the lower extremity, that’s foot to knee to groin.

Image result for popliteal fossa lymph nodes


C – Thankfully, painful biochemistry really isn’t all that common on Step 1. MCAD is a fatty acid oxidation disorder.
These disorders can be fatal, as affected individuals cannot break down fats into usable energy during times of fasting/starvation.
None of the other choices are fatty acid oxidation disorders (and consequently associated with a build-up of fatty acids)

Medium-chain acyl-CoA dehydrogenase deficiency, often known as MCAD deficiency or MCADD is a disorder of fatty acid oxidation that impairs the body’s ability to break down medium-chain fatty acids into acetyl-CoA.


E – Zoster is caused by a reactivation of latent varicella virus (aka chickenpox) from dorsal root ganglion.

A dorsal root ganglion (or spinal ganglion) (also known as a posterior root ganglion), is a cluster of nerve cell bodies (a ganglion) in a posterior root of a spinal nerve. The dorsal root ganglia contain the cell bodies of sensory neurons (afferent).

Image result for dorsal root ganglion varicella


C – Blood flow also increases during exercise. The more anaerobic metabolism you use and lactate build-up you have, the more hyperemia you need to clear out the waste products.


D – Irritable bowel syndrome is a diagnosis of exclusion (you have to make sure they don’t actually have an organic bowel pathology, like IBD). It is characterized by alternating bouts of diarrhea and constipation associated with psychological stress.


A – The correlation coefficient, R, describes the degree of association of two variables. When positive, the association is direct (positive). The closer to 1, the more tightly associated the variables are (the closer the dots will fall on a line). 0.9 is very high (very close to 1), so the points will fall near/on the line of best fit.


C – Acute abdominal pain in a fertile woman is very frequently going to be an ectopic question. Associated fun fact: the most common cause of secondary amenorrhea is pregnancy.


muscular spasm involving repeated, often rhythmic, contractions.
“the patient suffered partial seizures accompanied with clonus in the left arm”

B – Schizophrenics take antipsychotics which can (extremely rarely) cause neuroleptic malignant syndrome (NMS): rigidity, confusion, fever, autonomic instability. A related but distinct scenario is “serotonin syndrome,” which can be caused by a variety of antidepressants and related compounds. The clinical presentations share some similarities, so the medication history is particularly helpful.

Neuroleptic malignant syndrome (NMS) is a rare, but life-threatening, idiosyncratic reaction to neuroleptic medications that is characterized by fever, muscular rigidity, altered mental status, and autonomic dysfunction. … Atypical antipsychotic drugs that may cause NMS include the following: Olanzapine. Risperidone.

19E – The chromosome appears truncated/small, so something has been deleted. If something lost leads to cancer, then it is the loss of a tumor suppressor.


A – Esophageal dilation that tapers at a non-relaxing lower esophageal sphincter (the so-called “bird’s beak” appearance) is classic achalasia.

Achalasia is a serious condition that affects your esophagus. The lower esophageal sphincter (LES) is a valve that closes off the esophagus from the stomach. If you have achalasia, your LES fails to open up during swallowing, which it’s supposed to do.


B – HGPRT = high uric acid. Self-mutilating behavior (e.g. bad finger biting) is one of the more specific clinical features.

Phosphoribosyl pyrophosphate – Increased levels of PRPP is characterized by the overproduction and accumulation of uric acid leading to hyperuricemia and hyperuricosuria. It is one of the causes of gout.

Increased levels of PRPP are present in Lesch-Nyhan Syndrome. Decreased levels of hypoxanthine guanine phosphoribosyl transferase (HGPRT) causes this accumulation, as PRPP is a substrate used by HGPRT during purine salvage.

Lesch–Nyhan syndrome (LNS), also known as Nyhan’s syndrome and juvenile gout, is a rare inherited disorder caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT), produced by mutations in the HPRT gene located on the X chromosome. LNS affects about one in 380,000 live births.

Adenine phosphoribosyltransferase (APRT) deficiency is an inherited condition that affects the kidneys and urinary tract. The most common feature of this condition is recurrent kidney stones; urinary tract stones are also a frequent symptom. Kidney and urinary tract stones can create blockages in the urinary tract, causing pain during urination and difficulty releasing urine.


E – Those are sickle cells on the smear. LUQ pain on test questions almost always means splenic pathology. All sickle cell kids will eventually infarct their spleen.

Wright’s stain is a histologic stain that facilitates the differentiation of blood cell types. It is classically a mixture of eosin (red) and methylene blue dyes. It is used primarily to stain peripheral blood smears, urine samples, and bone marrow aspirates which are examined under a light microscope.

Autoimmune hemolytic anemia. Autoimmune hemolytic anemia (orautoimmune haemolytic anaemia; AIHA) occurs when antibodies directed against the person’s own red blood cells (RBCs) cause them to burst (lyse), leading to insufficient plasma concentration.

The aplastic crisis is temporary cessation of red cell production. Because of the markedly shortened red cell survival time in patients with sickle cell disease, a precipitous drop in hemoglobin occurs in the absence of adequate reticulocytosis.

Salmonella septicemia is a condition wherein the presence of Salmonella bacteria in the blood triggers a potentially life-threatening, whole-body inflammatory response. Recurrent Salmonella septicemia is classified as an AIDS-defining condition by the U.S. Centers for Disease Control and Prevention (CDC).


E – Profuse super-watery diarrhea means cholera (the so-called “rice water stool”). That said, regardless of the cause, you treat all causes of volume loss with volume replacement (normal saline)!

Doxycycline is an antibiotic that is used in the treatment of a number of types of infections caused by bacteria and protozoa. It is useful for bacterial pneumonia, acne, chlamydia infections, early Lyme disease, cholera and syphilis.

This medication is a combination of two antibiotics: sulfamethoxazole and trimethoprim. It is used to treat a wide variety of bacterial infections (such as middle ear, urine, respiratory, and intestinal infections). It is also used to prevent and treat a certain type of pneumonia (pneumocystis-type).

Ciprofloxacin is a fluoroquinolone (flor-o-KWIN-o-lone) antibiotic that fights bacteria in the body. Ciprofloxacin is used to treat different types of bacterial infections. It is also used to treat people who have been exposed to anthrax or certain types of plague.

Fluoroquinolone antibiotics can cause serious or disabling side effects. Ciprofloxacin should be used only for infections that cannot be treated with a safer antibiotic.


D – Tamoxifen is a selective estrogen receptor modulator (SERM). It blocks estrogen receptors in the breast (good to prevent breast cancer recurrence), but it actually activates uterine estrogen receptors and increases the risk of endometrial hyperplasia and endometrial carcinoma. Abnormal vaginal bleeding in a patient over the age of 35 should prompt an endometrial biopsy to rule out cancer.


Delavirdine is a non-nucleoside reverse transcriptase inhibitor marketed by ViiV Healthcare. It is used as part of highly active antiretroviral therapy for the treatment of human immunodeficiency virus type 1. 

Ritonavir, sold under the trade name Norvir, is an antiretroviral medication used along with other medications to treat HIV/AIDS This combination treatment is known as highly active antiretroviral therapy.

D – Learning how to interpret hepatitis panels is high yield. This patient has the Hepatitis B surface antigen (that the virus is making) but does not yet have the antibody against this antigen that confers immunity. Generally, antibodies to surface antigens are protective.


Folic acid deficiency anemia happens when your body does not have enough folic acid. Folic acid is one of the B vitamins, and it helps your body make new cells, including new red blood cells . Your body needs red blood cells to carry oxygen. … Most people get enough folic acid in the food they eat.

Vitamin A Deficiency. Vitamin A deficiency can result from inadequate intake, fat malabsorption, or liver disorders. Deficiency impairs immunity and hematopoiesis and causes rashes and typical ocular effects (eg, xerophthalmia, night blindness).

abnormal dryness of the conjunctiva and cornea of the eye, with inflammation and ridge formation, typically associated with vitamin A deficiency.
Vitamin B1 deficiency (thiamine)
What are the symptoms of thiamine deficiency?
Neurologic symptoms of thiamine deficiency are as follows:
  • Poor memory, irritability, sleep disturbance.
  • Wernicke encephalopathy, Korsakoff syndrome.
  • Bilateral, symmetrical lower extremities paresthesias, burning pain.
  • Muscle cramps.
  • Decreased vibratory position sensation.
  • Absent knee and ankle jerk.
  • Muscle atrophy.

Vitamin B6 deficiency (pyridoxine)

Vitamin B6 is also involved in the formation of myelin, a protein layer that forms around nerve cells. Vitamin B6 deficiency in adults may cause health problems affecting the nerves, skin, mucous membranes, and circulatory system. … High blood levels of the amino acid homocysteine may be a risk factor for heart disease.

Vitamin B12 deficiency (cobalamin)

VITAMIN B12 OR COBALAMIN DEFICIENCY occurs frequently (> 20%) among elderly people, but it is often unrecognized because the clinical manifestations are subtle; they are also potentially serious, particularly from a neuropsychiatric and hematological perspective. Causes of the deficiency include, most frequently, food-cobalamin malabsorption syndrome (> 60% of all cases), pernicious anemia (15%–20% of all cases), insufficient dietary intake and malabsorption. 

C – Classic Wernicke’s encephalopathy: confusion, jiggly eyes (ophthalmoplegia), and ataxia. It’s thiamine deficiency (same deficiency in beriberi). Add in anterograde amnesia and confabulation and you have a class USMLE presentation of Korsakoff’s psychosis (Wernicke-Korsakoff syndrome).


Amitriptyline, sold under the brand name Elavil among others, is a medicine used to treat a number of mental illnesses.[2] These include major depressive disorder and anxiety disorder, and less commonly attention deficit hyperactivity disorder and bipolar disorder.[2][3] Other uses include prevention of migraines, treatment of neuropathic pain such as fibromyalgia and postherpetic neuralgia, and less commonly insomnia.[2][4] It is in the tricyclic antidepressant (TCA) class and its exact mechanism of action is unclear.[2] Amitriptyline is taken by mouth.[2]

Phenytoin, sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures, partial seizures, but not absence seizures.

Sumatriptan is a medication used for the treatment of migraine and cluster headaches. It is a synthetic drug belonging to the triptan class.

E – Intermittent unilateral throbbing/pulsatile headaches are migrainous, especially if associated with nausea/vomiting, photophobia, phonophobia, etc. Triptans are drugs of choice for the treatment of acute migraine episodes. Tricyclic antidepressants (TCAs) like amitriptyline are used for migraine prophylaxis. Oxygen is a treatment for cluster headache


C – Common sense is key, particularly for counseling-type questions. Patients have autonomy and can do whatever they want; it’s your job to explain the risks and benefits. The patients ultimately make their own treatment choices.


H – It’s okay to be normal, especially on developmental and psychiatry questions.


Warfarin, sold under the brand name Coumadin among others, is a medication that is used as a blood thinner.

Vitamin K is a fat-soluble vitamin that is most well known for the important role it plays in blood clotting. However, vitamin K is also absolutely essential to building strong bones, preventing heart disease, and crucial part of other bodily processes. The ability to bind calcium ions (Ca2+) is required for the activation of the seven vitamin K-dependent blood clotting (‘coagulation‘) factors (e.g., prothrombin), or proteins, in the series of events that stop bleeding through clot formation (‘coagulation cascade’).

INR monitoring is essential for all patients treated with warfarin

International Normalised Ratio (INR) testing is well established as an integral part of warfarin treatment. INR has a critical role in maintaining the warfarin response within a therapeutic range, to provide the benefits of anticoagulation, while avoiding the risks of haemorrhage (Figure 1).

Therapeutic monitoring of warfarin treatment requires two key elements to be undertaken if it is to be successful: the measurement of the INR and an interpretation of the result in order to advise on dosage of warfarin and when the next test should be performed.

D – You need to memorize the list of drugs that induce and inhibit CYP450. Warfarin has oodles and oodles of drug reactions for this reason with potentially dire consequences.


C – The only reasonable choice is always the correct one. Address patient concerns and respect their autonomy, even if they seem silly.


Thrombotic thrombocytopenic purpura (TTP) is a rare blood disorder. In TTP, blood clots form in small blood vessels throughout the body. The clots can limit or block the flow of oxygen-rich blood to the body’s organs, such as the brain, kidneys, and heart. As a result, serious health problems can develop. Hemolytic-uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are microangiopathic disorders—that is, they are characterized by abnormalities (chiefly blood clots) that occur within the small blood vessels of the body.

Acute megakaryoblastic leukemia (AMKL) is a subtype of acute myeloid leukemia (AML) characterized by abnormal megakaryoblasts that express platelet-specific surface glycoprotein. Bone marrow biopsy frequently demonstrates extensive myelofibrosis, often making aspiration in these patients difficult. AMKL is extremely rare in adults, occurring in only 1% of AML patients.1 This is in contrast to children, where it comprises between 4% and 15% of AML patients.2,3 In pediatrics, the disease is divided into 2 major subgroups: AMKL in patients with Down syndrome (DS-AMKL) and AMKL in patients without DS (non–DS-AMKL).

Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal white blood cells that build up in the bone marrow and interfere with the production of normal blood cells. AML is the most common acute leukemia affecting adults, and its incidence increases with age. Although AML is a relatively rare disease, accounting for roughly 1.2% of cancer deaths in the United States,[1] its incidence is expected to increase as the population ages.

The symptoms of AML are caused by replacement of normal bone marrow with leukemic cells, which causes a drop in red blood cells, platelets, and normal white blood cells. These symptoms include fatigue, shortness of breath, easy bruising and bleeding, and increased risk of infection. Several risk factors and chromosomal abnormalities have been identified, but the specific cause is not clear. As an acute leukemia, AML progresses rapidly and is typically fatal within weeks or months if left untreated.

AML has several subtypes; treatment and prognosis vary among subtypes. AML is cured in 35–40% of people under 60 years old and 5–15% over 60 years old. Older people who are not able to withstand intensive chemotherapy have an average survival of 5–10 months.[2]

AML is treated initially with chemotherapy aimed at inducing remission; people may go on to receive additional chemotherapy or a hematopoietic stem cell transplant. Recent research into the genetics of AML has resulted in the availability of tests that can predict which drug or drugs may work best for a particular person, as well as how long that person is likely to survive. The treatment and prognosis of AML differ from those of chronic myelogenous leukemia (CML) in part because the cellular differentiation is not the same; AML involves higher percentages of dedifferentiated and undifferentiated cells, including more blasts (myeloblasts, monoblasts, and megakaryoblasts).

Aplastic anemia is deficiency of all types of blood cell caused by failure of bone marrow development.

(IMMUNE) Idiopathic thrombocytopenic purpura (ITP) is a bleeding disorder in which the immune system destroys platelets, which are necessary for normal blood clotting. People with the disease have too few platelets in the blood. ITP is sometimes called immune thrombocytopenic purpura or simply, immune thrombocytopenia.

Epstein-Barr virus, or EBV, is one of the most common human viruses in the world. It spreads primarily through saliva. EBV can cause infectious mononucleosis, also called mono, and other illnesses. Most people will get infected with EBV in their lifetime and will not have any symptoms.

Papovavirus, any virus in the families Papillomaviridae and Polyomaviridae. Papovaviruses are responsible for a variety of abnormal growths in animals: warts (papillomas) in humans, dogs, and other animals; cervical cancer in women; tumours (polyomas) in mice; and vacuoles (open areas) in cells of monkeys.

D – ITP causes immune-mediated consumption of platelets, hence the low platelet count and petechiae. The bone marrow biopsy results demonstrate that the body has appropriately increased platelet production, meaning that this is not a platelet production issue. While TTP has a similar acronym, it’s an entirely different disease with a classic pentad: thrombocytopenia (low platelet count), microangiopathic hemolytic anemia, altered mental status, renal failure, and fever.

20,000/mm3 (too low)

A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. Having more than 450,000 platelets is a condition called thrombocytosis; having less than 150,000 is known as thrombocytopenia. You get your platelet number from a routine blood test called a complete blood count (CBC).


Vital capacity – the greatest volume of air that can be expelled from the lungs after taking the deepest possible breath.

Forced expiratory volume (FEV) measures how much air a person can exhale during a forced breath. The amount of air exhaled may be measured during the first (FEV1), second (FEV2), and/or third seconds (FEV3) of the forced breath. Forcedvital capacity (FVC) is the total amount of air exhaled during the FEV test.

Forced expiratory volume (FEV) measures how much air a person can exhale during a forced breath. The amount of air exhaled may be measured during the first (FEV1), second (FEV2), and/or third seconds (FEV3) of the forced breath.

Forced vital capacity (FVC) is the total amount of air exhaled during the FEV test.

Forced expiratory volume and forced vital capacity are lung function tests that are measured during spirometry. Forced expiratory volume is the most important measurement of lung function. It is used to:

Diagnose obstructive lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). A person who has asthma or COPD has a lower FEV1 result than a healthy person. See how well medicines used to improve breathing are working.
Check if lung disease is getting worse. Decreases in the FEV1 value may mean the lung disease is getting worse.

J (juxtacapillary) receptors (or pulmonary C-fiber receptors) are sensory nerve endings located within the alveolar walls in juxtaposition to the pulmonary capillaries of the lung and are innervated by fibers of the vagus nerve.

Pulmonary compliance (or lung compliance) is a measure of the lung‘s ability to stretch and expand (distensability of elastic tissue). In clinical practice it is separated into two different measurements, static compliance and dynamic compliance.

C – Middle-aged woman with progressive shortness of breath? Think of idiopathic pulmonary fibrosis, a restrictive lung disease.


Muscle fasciculations – Muscle twitching is caused by minor muscle contractions in the area, or uncontrollable twitching of a muscle group that is served by a single motor nerve fiber.

Hyperreflexia (or hyper-reflexia) is defined as overactive or overresponsive reflexes. Examples of this can include twitching or spastic tendencies, which are indicative of upper motor neuron disease as well as the lessening or loss of control ordinarily exerted by higher brain centers of lower neural pathways (disinhibition).

Babinski reflex is one of the reflexes that occurs in infants. Reflexes are responses that occur when the body receives a certain stimulus. The Babinski reflex occurs after the sole of the foot has been firmly stroked. The big toe then moves upward or toward the top surface of the foot. The other toes fan out.

A Babinski reflex in an older child or an adult is abnormal and is a sign of a problem in the brain or spinal cord. A Babinski reflex that is present on one side but not the other is also abnormal, and it can indicate which side of the brain is involved.

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease and motor neurone disease (MND), is a specific disease that causes the death of neurons which control voluntary muscles.Some also use the term “motor neuron disease” for a group of conditions of which ALS is the most common. ALS is characterized by stiff muscles, muscle twitching, and gradually worsening weakness due to muscles decreasing in size. This results in difficulty in speaking, swallowing, and eventually breathing.

Alzheimer’s is a type of dementia that causes problems with memory, thinking and behavior. Symptoms usually develop slowly and get worse over time, becoming severe enough to interfere with daily tasks.

What are the symptoms of Guillain Barre Syndrome?
The symptoms of Guillain-Barre include: tingling or prickly sensations in your fingers and toes. muscle weakness in your legs that travels to your upper body and gets worse over time. difficulty walking steadily.

Guillain-Barre (gee-YAH-buh-RAY) syndrome is a rare disorder in which your body’s immune system attacks your nerves. Weakness and tingling in your extremities are usually the first symptoms.

These sensations can quickly spread, eventually paralyzing your whole body. In its most severe form Guillain-Barre syndrome is a medical emergency. Most people with the condition must be hospitalized to receive treatment.

A cerebral infarction is an area of necrotic tissue in the brain resulting from a blockage or narrowing in the arteries supplying blood and oxygen to the brain.

Multiple sclerosis (MS) is an unpredictable, often disabling disease of the central nervous system that disrupts the flow of information within the brain, and between the brain and body.

A – A mix of upper (hyperreflexia, babinski) and lower (fasiculations, atrophy) motor neuron signs means ALS. Know your UMN/LMN signs.

Image result for UMN/LMN signs.


Adenosine deaminase (also known as adenosine aminohydrolase, or ADA) is an enzyme (EC involved in purine metabolism. It is needed for the breakdown of adenosine from food and for the turnover of nucleic acids in tissues.

Adenosine deaminase deficiency, also called ADA deficiency or ADA-SCID, is an autosomal recessive metabolic disorder that causes immunodeficiency. It occurs in fewer than one in 100,000 live births worldwide. It accounts for about 15% of all cases of severe combined immunodeficiency (SCID).

Adenosine kinase deficiency disrupts the methionine cycle and causes hypermethioninemia, encephalopathy, and abnormal liver function.

In molecular biology, Adenylosuccinate synthase (or adenylosuccinate synthetase) (EC is an enzyme that plays an important role in purine biosynthesis.

LeschNyhan syndrome (LNS), also known as Nyhan’s syndrome and juvenile gout, is a rare inherited disorder caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT), produced by mutationsin the HPRT gene located on the X chromosome. LNS affects about one in 380,000 live births.

Ribonucleotide reductase (RNR), also known as ribonucleoside diphosphate reductase, is an enzyme that catalyzes the formation of deoxyribonucleotides from ribonucleotides.[1] Deoxyribonucleotides in turn are used in the synthesis of DNA.

Adenine phosphoribosyltransferase (APRTase) is an enzyme encoded by the APRT gene, found in humans on chromosome 16.[3] It is part of the Type I PRTase family and is involved in the nucleotide salvage pathway, which provides an alternative to nucleotide biosynthesis de novo in humans and most other animals.[4] In parasitic protozoa such as giardia, APRTase provides the sole mechanism by which adenine can be produced.[5] APRTase deficiency contributes to the formation of kidney stones (urolithiasis) and to potential kidney failure.[6]

Severe combined immunodeficiency disease (SCID) refers to a group of potentially fatal disorders due to a combined loss of function of both T- and B-lymphocytes. There are at least 13 known and characterized genetic causes of SCID. The most common (45%) cause of SCID is the X-linked recessive disorder resulting from loss of function of the common gamma (γ) chain of the T-cell receptor and other interleukin (IL) receptors. The second most common (15%) form of SCID is an autosomal recessive disorder caused by defects in the activity of the purine nucleotide catabolism enzyme, adenosine deaminase (ADA). This form of SCID is inherited as an autosomal recessive disorder with an incidence rate as high as 1:200,000, although some studies report an incidence of 1:1,000,000. ADA catalyzes the irreversible deamination of adenosine and deoxyadenosine to inosine and 2′-deoxyinosine, respectively.

Reaction catalyzed by adenosine deaminase

B – Low B and T cells means severe combined immune deficiency (SCID), which is caused by adenosinde deaminase deficiency. Know your immune deficiencies.


Image result for pyknotic

500 Rads whole body is going to kill you.

Image result for eosinophilic cytoplasm apoptosis

A – Pyknosis and nuclear fragmentation are part of the process of apoptosis.


What does Niacin (nicotinic acid) do to the body?
B3 is one of 8 B vitamins. It is also known as niacin (nicotinic acid) and has 2 other forms, niacinamide (nicotinamide) and inositol hexanicotinate, which have different effects from niacin. All B vitamins help the body to convert food (carbohydrates) into fuel (glucose), which is used to produce energy.

The most common symptoms of niacin deficiency involve the skin, the digestive system, and the nervous system (3). The symptoms of pellagra are commonly referred to as the three D’s: dermatitis,diarrhea, and dementia. A fourth D, death, occurs ifpellagra is left untreated (10).

What is the cause of pellagra?
This can occur in 2 ways:
  • Primary pellagra results from inadequate niacin and/or tryptophan in the diet (mainly in developing countries or poverty stricken areas)
  • Secondary pellagra occurs when there is enough niacin in the diet but something prevents its absorption and processing.
Symptoms of thiamine deficiency are:
  • Headache.
  • Nausea.
  • Fatigue.
  • Irritability.
  • Depression.
  • Abdominal discomfort.

Thiamine was one of the first compounds recognized as a vitamin. Thiamine is involved in many body functions, including nervous system and muscle function, the flow of electrolytes in and out of nerve and muscle cells, digestion, and carbohydrate metabolism.

What is the deficiency of Vitamin b1?
Deficiency of vitamin B1 may lead to chronic diseases. One of them is Beriberi which is a neurological and cardiovascular disease. There are three types of beriberi. One of them, called wet beriberi has been associated with cardiovascular disease and is one of the most chronic symptoms of the deficiency of vitamin B1.
Riboflavin deficiency (vitamin B2)
Symptoms of riboflavin deficiency include sore throat, redness and swelling of the lining of the mouth and throat, cracks or sores on the outsides of the lips (cheliosis) and at the corners of the mouth (angular stomatitis), inflammation and redness of the tongue (magenta tongue), and a moist, scaly skin inflammation.
What does vitamin b2 do for your body?
Vitamin B2, also called riboflavin, is one of 8 B vitamins. All B vitamins help the body to convert food (carbohydrates) into fuel (glucose), which is used to produce energy. These B vitamins, often referred to as B-complex vitamins, also help the body metabolize fats and protein.
What is vitamin B 6 for?
Vitamin B6, also called pyridoxine, is a water-soluble nutrient that is part of the B vitamin family. B vitamins, including vitamin B6, help support adrenal function, help calm and maintain a healthy nervous system, and are necessary for key metabolic processes.
What does b12 do for you?
Vitamin B12 is vital for the formation of red blood cells, as well as for the proper functioning and health of nerve tissue. If left untreated, vitamin B12 deficiency, also known as B12 deficiency, can lead to anemia, as well as nerve and brain damage, which may eventually become irreversible.
What happens if you don t have enough vitamin B in your diet?
Along with vitamins B12, folate and vitamin C, vitamin B6 is critical for the production of blood cells. Deficiency can result in anemia as well as neurological problems, impaired immunity, and heart disease. Early symptoms of vitamin B6 deficiency include: Cracks in the corner of mouth.
WHAT IS A folate deficiency?
Folate deficiency is a low level of folic acid in the body. Also known as vitamin B9, it is involved in adenosine, guanine, and thymidine synthesis (part of DNA synthesis). Signs of folate deficiency are often subtle. Anemia is a late finding infolate deficiency.
E – Subacute combined degeneration (progressive peripheral sensory and motor loss) is a late sign of B12 deficiency, which is common in old people. On board exams, a geriatric patient who lives alone and may have a “tea and toast” diet is likely to have vitamin deficiencies, particularly of folate and B12.


E – You can often ignore the pictures. Endotracheal tubes irritate the sensitive respiratory mucosa, causing the more delicate pseudostratified ciliated epithelium to be replaced by metaplastic stratified squamous epithelium (the tissue most suited to areas of constant abrasion). When tissues are exposed to an atypical/noxious environment, they can become metaplastic as an adaptation (just as in Barrett’s esophagus, when esophageal stratified squamous tissue becomes simple columnar epithelium [like stomach/bowel] after prolonged exposure to acidic gastric secretions.)


A – Phenylephrine is an alpha-agonist nasal spray and oral medication that often shows up on exams. Oxymetazoline (Afrin) is a similar alpha-agonist nasal spray. Pseudoephedrine is another decongestant with a similar MOA that’s less common now that it’s a federally monitored component of methamphetamine production. Topical alpha agonist decongestant are physically addictive and can cause miserable rebound congestion (rhinitis medicamentosa). Systemic formulations can cause hypertension and worsen prostate problems by causing prostatic smooth muscle constriction. Just remember that tamsolusin (Flomax) is an alpha-5a antagonist, which relaxes prostate muscle.


B – Memorize aspirin’s acid-base effects: metabolic acidosis and respiratory alkalosis. Note, this is actual respiratory alkalosis, not simply normal respiratory compensation for metabolic acidosis.


C – Prolactin is elevated (hence the amenorrhea and galactorrhea). Your first thought is a pituitary microadenoma, which isn’t an answer choice. Then you remember that dopamine is also known as “prolactin inhibiting hormone” and that a lesion of the infundibular stalk would prevent dopamine released by the hypothalamus from reaching the pituitary gland to inhibit prolactin secretion, thus causing hyperprolactinemia. That’s a mouthful.


A – Turner syndrome (you may remember lymphedema of the neck by another name: cystic hygroma). The 45,X gives it away though anyway. Mosaic Turner’s syndrome and the mosaic trisomies result from nondisjunction during mitosis. In total monosomy/trisomies, the cause is nondisjunction during meiosis. Uniparental disomy is essentially only tested via the Prader-Willi and Angelman syndromes (chromosome 15).


C – GVHD sucks. Skin and GI lesions are especially common sites (mucosal tissues are rapidly dividing and thus prone to attack).


C – It’s just anatomy. What hip flexor is up in the abdomen near the appendix?
Image result for psoas major


E – Hypertension, headache, visual changes, etc during pregnancy mean preeclampsia. Once you get a seizure, it’s eclampsia. Treatment is rapid delivery of the fetus (with magnesium to prevent seizures).
Image result for preeclampsia.


B – Azotemia, hemoconcentration, and hypotension/tachycardia are all results of dehydration. This may lead to acute renal failure if allowed to continue (but this diagnosis requires a change in creatinine of 0.3).
Azotemia (azot, “nitrogen” + -emia, “blood condition”) is a medical condition characterized by abnormally high levels of nitrogen-containing compounds (such as urea, creatinine, various body waste compounds, and other nitrogen-rich compounds) in the blood.
Image result for azotemia