Early scleromyxedema with granulomatous histology mimicking generalized granuloma annulare: a diagnostic hurdle

Scleromyxedema is a rare primary cutaneous mucinosis characterized by generalized waxy papules, dermal mucin deposition, fibroblast proliferation, and fibrosis, frequently associated with monoclonal gammopathy. Granuloma annulare, in contrast, is a granulomatous dermatosis that may present with annular papules and plaques and is typically self-limiting. Diagnostic differentiation between these entities relies heavily on clinicopathologic correlation; however, overlap patterns may pose significant diagnostic challenges. We report a 77-year-old woman with multiple comorbidities presenting with a four-month history of mildly pruritic, erythematous, waxy papules arranged in linear arrays over the neck, trunk, forearms, and thighs. Initial clinical assessment favored generalized granuloma annulare. Histopathological examination demonstrated granulomatous inflammation in the papillary dermis without significant fibroblast proliferation or mucin deposition, suggestive of granuloma annulare. 
The patient initially responded to topical corticosteroids and narrowband ultraviolet B phototherapy, but later experienced disease recurrence with scleroderma and swallowing difficulty, prompting reconsideration of a granulomatous variant of scleromyxedema. Further investigations, including serum protein electrophoresis and immunofixation, were initiated to evaluate for monoclonal gammopathy. This case highlights the diagnostic complexity arising from histopathological overlap between generalized granuloma annulare and granulomatous variants of scleromyxedema. Recognition of atypical clinical progression and treatment resistance is essential to avoid delayed diagnosis of scleromyxedema, a condition with potential systemic implications requiring early systemic therapy.