Published Web Locationhttps://doi.org/10.5070/D363d311vc
PachydermodactylyDepartment of Dermatology, New York University, New York, New York
Raegan Hunt MD PhD, Rajni Mandal MD, Ruth Walters MD, Julie V Schaffer MD
Dermatology Online Journal 16 (11): 5
A 16-year-old boy presented to the Pediatric Dermatology Clinic at the Charles C. Harris Skin and Cancer Pavilion with a two-year history of asymptomatic swelling of fingers on both hands. His condition had remained undiagnosed after previous evaluation by several dermatologists and hand specialists. He initially had noticed increased fullness of his proximal left fourth digit. Several months later, he noted swelling of his left fifth digit and right second through fourth digits. The patient reported no pain, pruritus, restriction of movement, morning stiffness, or trauma. He also denied repetitive hand-rubbing movements although his mother stated that he had this habit as a child. Past medical history included allergic rhinitis and asthma. Similar hand findings were not present in any other members of his family.
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There was soft tissue swelling along the radial and ulnar aspects of the proximal interphalangeal joints of the right and (less prominently) left second, third, and fourth fingers; this gave the affected digits a fusiform appearance. Slightly pink, smooth, nodular swelling also was present on the proximal phalanges of the left fourth and fifth fingers. There was no erythema, warmth, or tenderness. All the hand joints had full range of motion without pain, and no joint effusions were evident. The toes were normal.
The erythrocyte sedimentation rate, C-reactive protein level, thyroid stimulating hormone level, and serum and urine protein electrophoresis were normal. Hand radiographs showed soft tissue swelling but no abnormalities of the joints or bones.
There is epidermal hyperplasia with acanthosis and hyperkeratosis. Collagen fibers in the reticular dermis are thickened and haphazardly arranged, with fibroblast hypercellularity and increased deposits of connective-tissue mucin.
Originally described by Bazex in 1973,  pachydermodactyly is characterized by asymptomatic thickening of the soft tissues that overlie the radial and ulnar aspects of the proximal interphalangeal joints [1, 2]. Fusiform swelling, which typically affects the second through fourth digits and occasionally involves the fifth digit occurs [3, 4]. Skin thickening or nodules sometimes extend to the dorsal aspect of the fingers, and a distal variant also has been identified. No tenderness, warmth, or reduced range of motion of the joints is observed, and radiographs and magnetic resonance imaging show soft tissue thickening but no abnormalities of the joint space or bones [5, 6]. A single case of deforming pachydermodactyly with nonerosive interphalangeal subluxation that resulted in ulnar deviation has been reported .
Pachydermodactyly develops most often in healthy adolescents and young adults (median age of 19 years), with a male-to-female ratio of approximately 4:1 [4, 8]. Repetitive mechanical trauma, such as that inflicted by habitual or tic-like hand movement patterns, was noted as a precipitating factor in 35 percent (33/94) of the patients reported to date . In some of these individuals, the ritualistic behaviors were related to sports activities or underlying conditions, such as obsessive-compulsive disorder and Asperger syndrome. Although familial occurrence and association with tuberous sclerosis or Ehlers-Danlos syndrome have been described, pachydermodactyly usually is an isolated, sporadic condition [9, 10].
Histopathologic features of pachydermodactyly include a hyperkeratotic, acanthotic epidermis and a thickened dermis with haphazardly arranged collagen bundles and fibroblasts. Types III and V collagens predominate [11, 12] and electron microscopy has demonstrated increased numbers of thin, collagen fibers . In many cases (including ours), dermal mucin deposition is evident . Although self-healing juvenile cutaneous mucinosis can present with fibromucinous nodules in a periarticular distribution on the hands, fusiform swelling of the lateral digits is not observed, and patients frequently have lesions elsewhere on the body.
Misdiagnosis of the periarticular abnormalities as manifestations of polyarticular juvenile idiopathic arthritis may lead to needless investigations and inappropriate treatment [14, 15]. In pachydermodactyly, patients with repetitive hand movements, appreciable improvement has been observed after cessation of the traumatic activity [16, 17]. Intralesional triamcinolone injections and localized surgical resection also have resulted in reduction of soft tissue swelling in some cases [3, 18].
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