Diffuse cutaneous reticulohistiocytosis

Area of Science:

• Dermatology
• Oncology
• Pathology

Background:

• Multicentric reticulohistiocytosis (MRH) is a rare systemic histiocytic disorder typically associated with arthritis.
• Cutaneous manifestations of MRH can vary, including papules, nodules, and plaques.

Observation:

• A 65-year-old man presented with a year-long, asymptomatic, diffuse cutaneous eruption of reddish-brown papules.
• Skin lesions exhibited morphologic, light microscopic, and ultrastructural features characteristic of MRH.
• The patient showed no clinical, laboratory, or radiographic evidence of arthritis or systemic involvement.

Findings:

• The cutaneous eruption of MRH resolved spontaneously after 17 months.
• Subacute myelogenous leukemia developed in the patient several weeks after the skin lesions involuted.
• Histopathological findings were consistent with MRH, despite the absence of systemic disease.

Implications:

• This case suggests that diffuse cutaneous reticulohistiocytosis without systemic involvement may represent a distinct clinical expression within the spectrum of MRH.
• The findings support the hypothesis that isolated reticulohistiocytomas, diffuse cutaneous reticulohistiocytosis, and systemic MRH share common etiologic and pathogenetic mechanisms.
• Further research is warranted to elucidate the relationship between cutaneous histiocytic disorders and hematologic malignancies.