Background: Mastocytosis is comprised of a group of heterogeneous diseases involving various organs. Urticaria pigmentosa is the most common manifestation of cutaneous mastocytosis; others include mastocytoma, diffuse mastocytosis, and telangiectasia macularis eruptiva perstans.
Methods: We describe a case of indolent mastocytosis presenting as scarring alopecia. The scalp biopsy revealed a perifollicular and dermal inflammatory infiltrate composed predominantly of mast cells, which was confirmed by tryptase and Giemsa stains.
Results: The preponderance of mast cells in the biopsy prompted testing for urine N-methylhistamine levels, which were elevated and confirmed the diagnosis of mastocytosis. This is the first report of mastocytosis presenting as scarring alopecia.
Conclusions: This case suggests that the diagnosis of mastocytosis should be entertained in patients presenting with scarring alopecia accompanied by an intense mast cell infiltrate on scalp biopsy and also supports the notion that mast cells may be involved in the pathogenesis of alopecia.