Microbiology, Parvoviridae Erythrovirus (Parovirus B19), Uncategorized

Parvoviridae Erythrovirus (Parovirus B19, Slapped-cheek rash, fifth disease, transient aplastic anemia crisis)

Reference: Lippincott’s Microcards

Erythema infectiosum is called ‘fifth disease’ because it is one of the five most common pediatric diseases with rash.

DNA virus – icosahedral nucleocapsid – nonenveloped – SS linear – Paroviridae – Erythrovirus

Clinical case
An African American girl with sickle cell anemia visits the doctor after developing weakness, fatigue, and pallor. She tells her physician that that several days before, she felt a fever, headache, and muscle aching. She also began to feel joint pain and developed a rash that had a ‘SLAPPED-FACE’ appearance on her face. A blood test reveals severe anemia, as well as a decline in neutrophils and lymphocytes. The myeloid lineage seems normal. Serology confirms the diagnosis, and the doctor orders a transfusion of erythrocytes to prevent life-threatening anemia.

Anemia is a decrease in number of red blood cells (RBCs) or reduced quantity of hemoglobin in the blood.

Clinical Presentation
erythema infectiosum (‘fifth disease’)
transient aplastic anemia crisis
Pathobiology
Inoculates nasal cavity – 6-day incubation – viremia and fever – virus infects and lyses erythroid precurser cells in the bone marrow – mildly reduced reticulocytes, lymphocytes, neutrophils, platelets (normal hosts can tolerate lack of erythropoiesis for one week)
Immune complexes form and deposit – erythema infectiosum: rash with ‘slapped cheek’ appearance, arthralgias, for several days.
In patients requiring increased erthyropoiesis, (e.g., sickle cell anemia, thalassemias) – transient aplastic crisis: severe reticulocytopenia, normal myeloid lineage.
Wikipedia –
Myeloid: The term myeloid is an adjective that relates to the granulocyte precursor cell in bone marrow or spinal cord, or a resemblance to the marrow or spinal cord. For example, myeloid leukemia is leukemia that arises from abnormal growth in the blood-forming tissue of the bone marrow.[1]
Diagnosis
Detect viral DNA
Serology
Treatment
Supportive: RNC transfusion in immunodeficient patient: Ig transfer
Quick facts
In immunodeficient patients, parvovirus infection can lead to chronic severe anemia. 
Fetuses, who require higher RBC production and are immunodeficient, are especially vulnerable to parovirus infections. Infected fetuses may develop severe anemia and hydrops fetalis.
Erythema infectiosum is called ‘fifth disease’ because it is one of the five most common pediatric diseases with rash.
Study tip:
Five most common pediatric diseases with rash –
MEASLES (measles virus)
RUBELLA (rubella virus)
SCARLET FEVER (S.pyogens)
ROSEOLA (HHV 6)
ERYTHEMA INFECTIOSUM (parvovirus B19)

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