Arthritis or maybe not? Pachydermodactyly: the great mimicker of juvenile idiopathic arthritis

Arthritis in the paediatric population is the hallmark of many rheumatic inflammatory diseases, as well as other cutaneous, infectious, or neoplastic conditions. It can be quite devastating, whereby prompt recognition and treatment of these disorders are essential. However, arthritis can sometimes be mistaken for other cutaneous or genetic conditions leading to misdiagnosis and overtreatment. Pachydermodactyly is a rare and benign form of digital fibromatosis, usually manifested by swelling of the proximal interphalangeal joints of both hands, mimicking arthritis. The authors report a case of a 12-year-old boy with a one-year history of painless swelling of the proximal interphalangeal joints of both hands that was referred to the Paediatric Rheumatology department due to the suspicion of juvenile idiopathic arthritis. The diagnostic work-up was unremarkable, and the patient remained asymptomatic over an 18-month follow-up period. A diagnosis of pachydermodactyly was assumed and no treatment was introduced, given the benign nature of the disorder and absence of symptoms. Therefore, it was possible to safely discharge the patient from the Paediatric Rheumatology clinic.