Microcards: Lyme Disease – Borrelia Burgdorferi

Published on December 29, 2013

From Lippincott’s Microcards

Clinical case
 A woman seeks medical attention for a skin rash expanding on her arm over several days. Her doctor notes an annular, red rash with a CLEAR AREA in the center. The woman also complains of a fever, headache, arthralgias (joint pain), and stiffness of the neck following the onset of of the rash by a week. When asked if bitten by any insects, the woman cannot answer definitively, but she does remember seeing a TICK on her sleeping bag during a camping trip to CONNECTICUT last month. The doctor prescribes DOXYCYCLINE (Tetracycline antibiotic) and checks the woman’s electrocardiogram to ensure no heart problems have developed as a result of her illness.

Clinical presentation
Stage 1 –
Erythema chronicum migrans
Stage 2 –
CNS: Bell’s palsy, aseptic meningitis, peripheral neuropathy
CV: carditis, AV nodal block
Skin: secondary annular lesions
Joints: migratory myalgias (muscle pain), transient arthritis
Stage 3 –
chronic arthritis, encephalopathy, acrodermatitis chronicum atrophicans

Pathobiology
Carried in small mammals such as mice – Ixodes tick transmits from mice to humans – spirochetes disseminate
systematically –
Stage 1 (10 days after bite): at inoculation site, bacteria multiply and and migrate outward – generate a spreading annular red lesion surrounding clear bite mark (erythema chronium migrans), flu-like symptoms
Stage 2 (weeks later): disseminated spirochetes proliferate – inflammatory response damages: CNS, heart, skin, joints
Stage 3 (months-years later): persistent infection – inflammatory damage in joints, brain, and local areas of skin atrophy (acrodermititis chronicum atrophicans)


Diagnosis
skin biopsy: spirochete, motile under dark-field microscopy, serology

Treatment
doxycyline or amoxycillin for stage 1
ceftriaxone for later stages

Quick Facts
Early detection of tick can prevent disease becuase tick feeding requires 24 hours to transmit sufficient inoculum. Lyme disease is the MOST COMMON vector-borne disease

STUDY TIP: Most common diseases in the US spread by vectors are LYME DISEASE, ROCKY MOUNTAIN SPOTTED FEVER, TULAREMIA

My Memory cue “If you eat at the Italian restaurant, Borrelia Burgdorferi, you may catch Lyme Disease!”

Images

Spirochetes – Giemsa & silver stains, microaerophilic – B. burgdorferi

Erythema migrans in Lyme disease

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