Pediatric Bullous Mastocytosis: Diagnostic Challenges and Therapeutic Strategies

Abstract Background Mastocytosis is a rare disorder characterized by abnormal proliferation and accumulation of mast cells. In children, it is most often limited to the skin. Diffuse cutaneous mastocytosis is the rarest form and typically presents during infancy, frequently with extensive bullous lesions. Due to its rarity and clinical resemblance to other bullous dermatoses, early diagnosis remains challenging. Case presentation We report the case of a 9-month-old female infant admitted for an extensive pruritic bullous and ecchymotic eruption involving the thorax, limbs, and scalp. Physical examination revealed thickened infiltrated skin and a positive Darier’s sign, while mucous membranes were spared. Routine laboratory investigations were normal. Skin biopsy showed a dense subepidermal dermal infiltrate composed predominantly of mast cells arranged in confluent sheets. Immunohistochemical staining demonstrated strong and diffuse CD117 positivity. Serum tryptase levels were elevated, supporting the diagnosis of diffuse cutaneous mastocytosis. The patient was treated with topical corticosteroids, sterile dressings, and oral antihistamines, with complete resolution of skin lesions and no systemic complications. Conclusion Diffuse cutaneous mastocytosis should be considered in infants presenting with bullous skin lesions. Histological and immunohistochemical confirmation is essential for diagnosis. Although prognosis is generally favorable, careful follow-up is required due to the risk of severe mediator-related manifestations. Clinical trial number: not applicable