RESUMEN
A boy presented initially to a Rheumatology clinic with a three year history of asymptomatic swelling of the third to fourth proximal interphalangeal (PIP) joints bilaterally. A presumptive diagnosis of seronegative arthritis was made. Sulfasalazine was commenced without improvement and resulted in mood disturbance. Blood tests including ESR, lupus anticoagulant, rheumatoid factor and CCP antibodies were unremarkable. Hand radiographs were normal. MRI showed oedema within soft tissues around PIP joints. His care was transferred to the Rheumatology unit in our hospital and the rheumatological diagnosis was revised; sulfasalazine was stopped and skin biopsy organised. Onward referral to Dermatology was made. Examination revealed symmetrical swelling and thickening of soft tissues on PIP joints with no evidence of joint synovitis. He denied habitual behaviour but was noted to rub his fingers subconsciously. With this as a cause of repetitive minor trauma, a clinical diagnosis of pachydermodactyly was made. Skin biopsy was supportive showing a dermis with coarse collagen. Pachydermodactyly is rare. This case highlights the importance of prompt recognition to avoid invasive and excessive diagnostic procedures as well as unnecessary immunosuppression.