Cutaneous plasmacytosis: A rare entity with unique presentation.

Area of Science:

• Dermatology
• Pathology
• Immunology

Background:

• Primary cutaneous plasmacytosis is an uncommon dermatological condition characterized by widespread skin lesions.
• Most reported cases originate from Japan, making international documentation rare.

Observation:

• A 50-year-old female of Mongolian descent from Mizoram, India, presented with extensive violaceous maculo-papular plaques on the face, trunk, and extremities.
• Skin biopsies revealed dense perivascular and periadnexal mature plasma cell infiltration.
• The patient also exhibited lymphadenopathy with cervical lymph node biopsy showing effacement by plasma cells.

Findings:

• Serum protein electrophoresis and urine Bence Jones protein tests were negative for M band and monoclonal proteins.
• Immunohistochemistry confirmed a polyclonal nature of plasma cells in both skin and lymph node biopsies, with no kappa or lambda light chain restriction.
• The case presented classical clinical features alongside detailed histopathological and immunohistochemical documentation.

Implications:

• This case expands the geographical documentation of primary cutaneous plasmacytosis.
• It highlights the importance of histopathological and immunohistochemical analysis for accurate diagnosis.
• Understanding the polyclonal nature of plasma cell infiltration is crucial for differentiating from plasma cell neoplasms.