A 9-year-old boy was referred to the pediatric rheumatology clinic in order to assess the appearance of persistent swelling involving several fingers in a bilateral and symmetrical mode, without any other joint involvement elsewhere. Such a disturbance affected mainly the third and fourth fingers (and, in a lesser extent, the second digits, too) and was limited to the proximal interphalangeal joints (Figs. 1A, B). The patient was sent with a clinical suspicion of juvenile idiopathic arthritis (JIA), but no concomitant symptoms, such as pain, joint stiffness, movement impairment, and local redness, were reported; moreover, blood cell count and the inflammatory parameters (C-reactive protein and erythrocyte sedimentation rate) resulted to be within the reference range. No history of evident local trauma was recorded. Conventional radiographs showed no epiphyseal bone enlargement of phalanges, but fusiform and symmetric soft tissue thickening only (Fig. 2A). These findings were supported by ultrasonography, which excluded the presence of abnormalities of the joint spaces and confirmed the thickening of soft tissue around the proximal interphalangeal joint, as evidenced in Figure 2B. Thus, a final diagnosis of pachydermodactyly was made, which is a form of acquired and benign digital fibromatosis developing most often in adolescents. This can mimic the clinical findings of JIA and, indeed, the most important differential diagnosis is polyarticular JIA. However, a careful clinical evaluation supported by noninvasive investigations (blood tests, radiographs, and especially ultrasonography) can avoid both needless diagnostic procedures (including skin biopsy) and misdiagnosis leading to inappropriate treatments.