Bone and Soft-Tissue Disorders
= heterogeneous zoonosis with geographical variation in animal reservoir + tick species + spirochete subspecies
Agent: spirochete Borrelia burgdorferi transmitted by tick bite Ixodes dammini; in Europe Borrelia garinii
Histo: inflammatory synovial fluid, hypertrophic synovia with vascular proliferation + cellular infiltration
- endemic areas: Lyme and Old Lyme, Connecticut (first recognized location); now throughout USA, Europe, Australia
- recurrent attacks of arthralgias within days to 2 years after tick bite (80%); history of erythema chronicum migrans
Location: mono- / oligoarthritis of large joints (especially knee)
- erosion of cartilage / bone (4%)
- NO neuroimaging manifestations (frequent)
- painful meningoradiculitis (= Bannwarth syndrome)
- abnormal smooth leptomeningeal enhancement with cranial or spinal nerve involvement
- enhancing periventricular + callososeptal + infratentorial white matter lesions ← perivascular extension of lymphocytic inflammation (DDx: multiple sclerosis)
Rx: antibiotics
Posttreatment Lyme disease (10–20%) = syndrome due to autoimmune effects of molecular mimicry and antigen cross-reactivity
DDx:
- Rheumatic fever
- Rheumatoid arthritis
- Gonococcal arthritis
- Reiter syndrome