Rare case of Lyme borreliosis in a patient presenting with dactylitis and skin rash.

An immunocompetent male in his 70s was diagnosed with psoriatic arthritis based on dactylitis, onycholysis of the nails and scalp psoriasis. He was treated with corticosteroids, methotrexate and local corticosteroid injections without improvements in his symptoms. When tumor necrosis factor-alpha inhibitor treatment was introduced, the symptoms worsened and dactylitis of all digits and a bluish-red rash were observed on the extensor side of the left hand and arm. At this point, a skin biopsy was performed showing histopathological changes compatible with Lyme borreliosis and serum contained IgG antibodies against Borrelia burgdorferi It was concluded that he was suffering from acrodermatitis chronica atrophicans (ACA) and Lyme dactylitis. Ten days of phenoxymethylpenicillin treatment was initiated, and after 2 weeks, the dactylitis and ACA had regressed substantially. After 6 months, both had resolved. This case emphasises the need for clinical reassessment, when treatment is not effective.