Knuckle pads: an ancient disease frequently misdiagnosed because of minimal modern attention

Knuckle pads are benign painless papules and nodules that most commonly appear on the extensor surfaces of the proximal interphalangeal joints. Knuckle pads are frequently misdiagnosed due to their location overlying joints, which can lead to costly interventions and patient discomfort for a relatively harmless condition. We describe a 44-year-old woman who presented with mildly painful nodules on multiple bilateral proximal interphalangeal joints. The patient did not have a family history of fibromatosis and the rheumatoid factor was negative. Histology showed mild epidermal hyperkeratosis, papillomatosis, and acanthosis with a deep dermal, poorly circumscribed, proliferative nodule made of spindled myofibroblasts without cytological atypia. The diagnosis of knuckle pads was established based on the clinical and morphological presentation of the nodules. Treatment with intralesional triamcinolone acetonide injection produced significant clinical improvement. Our findings highlight the challenging diagnosis of knuckle pads and the importance of increasing the familiarity of knuckle pads in modern medical practice.