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Journal of Medical Cases

Case Report

Volume 4, Number 3, March 2013, pages 128-129

Knuckle Pads Versus Gottron’s Papules: Making a Differential Diagnosis

Knuckle pads most often occur in teenagers and young adults and should be included in the vast differential diagnosis of cutaneous lesions of the hands and feet. Confusion with cutaneous manifestations of rheumatologic diseases, like rheumatoid nodules or Gottron’s papules, may occur. Their recognition is essential for an adequate diagnosis and posterior orientation.

A 13 year-old caucasian boy presented with various erythematous hyperkeratotic plaques on the extensor surfaces of both hands, well-circumscribed, non-tender, overlying metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints that appeared 2 years ago (Fig. 1, 2). They had slowly growing and varied in size between 0.5 - 1.8 cm. There weren’t no other cutaneous lesions, namely on the feet, neither palmoplantar hyperkeratosis. The muscle strength examination was normal and he practiced sport in a regular basis (football) without any limitation. Personal and familiar antecedents were unremarkable, with no history of hearing loss. Initially, the diagnosis of Gottron’s papules was considered and an analytical evaluation was performed, revealing normal whole blood count, erythrocyte sedimentation rate (9 mm/h) and C-reactive protein (5.4 mg/L) and mildly elevated creatine phosphokinase (223 U/L, normal 38 - 174 U/L). The adolescent was referred to a Pediatric Rheumatologist who, in collaboration with a Dermatologist, concluded for the diagnosis of Knuckle pads. When questioned about repetitive trauma of the fingers, he confessed having the habit of chewing the lesions on a regular basis, especially when anxious. He wasńt concerned about cosmetic issues. Recommendation to avoid the traumatic stimuli was made.

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Figure 1. Knuckle pads overlying metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of both hands.

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Figure 2. Well-circumscribed, non-tender, erythematous hyperkeratotic plaques varying in size between 0.5 - 1.8 cm.

Knuckle pads appear as slowly growing cutaneous thickenings over the dorsal aspects of the digital joints [1]. They may be idiopathic or related to repetitive friction or pressure [2, 3] like in our case report. Knuckle pads occur in association with several fibrosing diseases (Dupuytren’s contracture, Ledderhosés syndrome and Peyronie’s disease) and are part of the autosomal dominant Bart-Pumphrey syndrome [1]. The latter was excluded as there weren’t palmoplantar hyperkeratosis or sensorineural deafness and familiar history was unremarkable. Knuckle pads may resolve spontaneously, especially when it’s possible to identify and remove the causative repetitive traumatism [2, 3]. However, most cases persist, are asymptomatic and don’t require treatment [1]. Because Knuckle pads are benign, their importance lies in differentiating them from more significant cutaneous disorders [1]. Differential diagnosis comprises Gottron’s papules, which share similar location [4]. Nevertheless, Gottron’s papules present distinctive features (flat papules, erythematous/violaceous, with central atrophy), consisting on a cutaneous manifestation of Juvenile Dermatomyositis [4, 5]). Juvenile Dermatomyositis was excluded since our case report didn’t fulfilled clinical criteria [5]: absence of typical skin rash and proximal muscle weakness and only mildly elevation of serum skeletal muscle enzymes (usually 5 to 20 times normal). The normal erythrocyte sedimentation rate also disfavored this diagnosis. Finally, differential diagnosis of Knuckle pads must also consider scars, granuloma annulare and rheumatoid nodules, among others [1].

Conflict of Interest

No conflict of interest for neither of the authors.

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Journal of Medical Cases is published by Elmer Press Inc.