Abstract:

Presentation: A 12-year-old female presents with a 2-year history of painless bilateral hand swelling, most prominent on the right third digit at the proximal interphalangeal (PIP) joint. MRI showed thickened ligaments and soft tissue edema but no inflammatory arthritis. Physical exam revealed non-tender skin thickening and swelling at all PIPs. Range of motion was intact. Punch biopsy of the right 3rd digit was obtained. Histologic Evaluation: Histologic sections showed acral skin with epidermal acanthosis and minimal spongiosis. The dermis contained increased fibroblasts between collagen bundles that are immunoreactive for CD34. Dermal mucin deposition was noted and highlighted by colloidal iron stain. Inflammation was absent. In conjunction with the clinical presentation, these findings were consistent with pachydermodactyly (PDD). Discussion: PDD is a rare entity with clinicopathologic correlation driving diagnosis. Beginning in adolescence with a male predominance, painless bilateral hand swelling most affecting the PIP joints occurs. Imaging shows soft tissue swelling with joint sparing. Etiology is hypothesized as trauma secondary to repeated digital manipulation (eg. knuckle cracking). Histologic evaluation shows epidermal hyperkeratosis and acanthosis. The dermis contains increased fibroblasts which are highlighted by CD34 stain. The fibroblasts exist between thickened and disorganized collagen bundles, and focal mucin deposits have been identified. Inflammation is absent. Treatment of PDD is not standardized but includes behavior cessation. Targeted injections or topical corticosteroids have been effective. Conclusion: This case highlights the histopathologic findings in PPD, which are rarely reported in the literature. The pathophysiology of increased fibroblasts and dermal mucin deposition remains uncertain; however, dermatopathologists should be aware of the histopathologic findings to avoid misdiagnosis (e.g., mucinosis and connective tissue disease).

Financial Disclosure:
No current or relevant financial relationships exist.

Menu

Caroline Mullins Underwood, MD