Working Diagnosis:
Lyme Arthritis, Pseudo-gout, and oblique undersurface tear of left lateral meniscus

Treatment:
The patient was seen a total of four times, during which joint aspirations were completed with 87 cc, 120 cc, 95 cc, and 37 cc of fluid removed at each visit respectively. During the third visit, a corticosteroid injection was administered at the time of aspiration. The patient’s Lyme arthritis was treated with Doxycycline 100 mg twice daily for 28 days total. He elected to complete a home exercise regimen for his lateral meniscal tear. He presented for his final visit 3 and a half weeks after his corticosteroid injection, at which time he had one final aspiration. He was able to achieve complete pain relief with no swelling and a return to complete activity by four weeks after Kenalog injection.

Outcome:
He had an evaluation for a separate issue 18 months later and noted no further left knee issues.

Author's Comments:
This represents an interesting case in which multiple pathologic entities present at once with contributing effects from each. This case also provides an example of a common presenting complaint which emphasizes a less common infectious etiology.

Editor's Comments:
Lyme arthritis should be considered high on the differential in a young person with an atraumatic effusion. Initial presentation of Lyme arthritis is frequently monoarticular. It should be treated with 4 weeks of oral antibiotics. Doxycycline is typically used as first line treatment for patients 8yo and older.


Given the age of this patient, pseudo-gout is an unusual finding. The incidence of calcium pyrophosphate deposition (CPPD) disease increases with age. CPPD commonly affects larger, weight bearing joints. The crystals involved with CPPD are composed of calcium pyrophosphate dihydrate. These crystals can create a lot of inflammation within the joint. Treatment includes NSAIDs and intra-articular steroid injection for acute attacks. Colchicine and low dose NSAIDs can be used on a more long term basis to prevent future attacks.

References:
Arvikar, Sheila L., and Allen C. Steere. "Lyme arthritis." Infectious disease clinics of North America 36.3 (2022): 563-577.
Baker P, Reading I, Cooper C, Coggon D. Knee disorders in the general population and their relation to occupation. Occup Environ Med. 2003;60(10):794-797.
Kobayashi, Takaaki, et al. "Mistaken identity: many diagnoses are frequently misattributed to Lyme disease." The American journal of medicine 135.4 (2022): 503-511.

Return To The Case Studies List.