D3.253 - Two Infant Cases Diagnosed with Bullous Mastocytosis, a Rare Variant of Diffuse Cutaneous Mastocytosis

Introduction and Objective

Mastocytosis is a heterogeneous group of disorders characterized by abnormal infiltration of mast cells in the skin and/or other organs. Cutaneous mastocytosis presenting predominantly with bullous lesions is extremely rare and may be confused with bullous impetigo, herpes simplex virus infection, and other immunobullous diseases. Herein, we present two infant cases diagnosed with bullous mastocytosis.

Case 1

A 51-day-old male infant presented with 3–4 lesions located on the occipital region, forehead, and above the left eyebrow, which initially appeared as erythema and subsequently progressed to oozing ulcerative lesions. Darier’s sign was positive. Serum tryptase level was 71.4 ng/mL (normal: <5 ng/mL; mastocytosis: >20 ng/mL). While investigations were planned with a preliminary diagnosis of mastocytosis, widespread bullous lesions developed one day after skin biopsy, starting from the biopsy site and spreading to the neck and back. Histopathological examination of the biopsy specimen was consistent with bullous mastocytosis.

Case 2

A 6-month-old male infant presented with widespread eruptions on the trunk, back, and shoulders, which began as erythema and progressed to bullous lesions overnight. There was no history of infection at presentation, although mild elevation of acute phase reactants was noted. Bullous impetigo and staphylococcal skin infection were excluded due to the absence of growth in wound cultures. Skin biopsy findings were compatible with bullous mastocytosis. Serum tryptase level was 102 ng/mL (normal: <5 ng/mL; mastocytosis: >20 ng/mL).

Conclusion

Bullous mastocytosis is a rare cutaneous disorder that can be confused with other bullous dermatoses and should be considered in the differential diagnosis. The diagnosis of cutaneous mastocytosis is based on clinical findings, histopathological examination, and exclusion of systemic involvement. Our cases highlight that trauma-inducing factors, including skin biopsy, may trigger disease exacerbation, emphasizing the need for caution. Accurate diagnosis is crucial due to the risk of anaphylaxis and the importance of long-term follow-up.