Anaphylaxis with clonal mast cells in normal looking skin - a new entity?

Area of Science:

• Immunology
• Dermatology
• Hematology

Background:

• Elevated serum tryptase (sBT) and anaphylaxis can suggest underlying mastocytosis.
• Aberrant mast cells (MC) have been observed in extracutaneous sites in patients with severe hypotension or anaphylaxis.

Purpose of the Study:

• To investigate mast cell alterations in normal neck skin of patients with anaphylaxis and urticaria who have elevated sBT.
• To explore the potential for skin biopsy to aid in diagnosing mast cell disorders.

Main Methods:

• Studied mast cells in normal neck skin biopsies from patients with anaphylaxis, urticaria, eczema, and systemic mastocytosis (SM).
• Compared mast cell counts and morphology (spindle shape) with CD25 antigen expression in patient groups and autopsy skin controls.
• Analyzed serum tryptase (sBT) levels.

Main Results:

• Anaphylaxis patients (n=14) had a mean of 93.1 MC/mm² in neck skin, compared to 39.1 MC/mm² in autopsy controls.
• Systemic mastocytosis (SM) patients (n=5) showed a higher mean MC count (124.4 MC/mm²).
• In anaphylaxis and SM patients, a significant proportion of MC were spindle-shaped and expressed CD25.

Conclusions:

• Normal skin can harbor clonal mast cells in anaphylaxis patients, suggesting skin biopsy is a valuable diagnostic tool.
• Proposed a skin score criteria including MC number, spindle shape, CD25 expression, c-Kit mutation, and sBT levels for mastocytosis diagnosis.
• Advocated for skin biopsy and MC analysis in anaphylaxis patients with elevated sBT, treating aberrant skin MC similar to mastocytosis patients.