P30 Blisters in a newborn: all that glitters is not gold

Abstract

Abstract Mastocytosis is a rare and clinically heterogeneous disease characterized by abnormal accumulation of mast cells in various tissues. There are three major types of cutaneous mastocytosis (CM): diffuse cutaneous mastocytosis (DCM), urticaria pigmentosa and solitary mastocytoma, which is the most common form before the age of 3 months: 90% of CM cases present before 2 years of age, and congenital mastocytosis has been described in 23% of those. Solitary mastocytoma has been associated with a mutation of the KIT gene. A male infant was born at 39 weeks, with a large, indurated, blistering, ulcerated plaque containing yellow serous fluid affecting half his right calf. His nails and oral mucosa were normal. Our centre was contacted on suspected diagnosis of inherited epidermolysis bullosa (EB). There was no family history of EB, and the parents were not related. Initial testing showed a PCR positive for HSV type 1 and treatment with aciclovir and cefotaxime was initiated. There was no improvement after 2 weeks of treatment. Viral and bacterial skin swab were negative. A skin biopsy and ultrasound were performed showing extensive superficial hypoechoic lesion and reactive popliteal lymph nodes and the biopsy confirmed the diagnosis of mastocytoma. Bloods including tryptase level and abdominal ultrasound were normal. The lesion healed within 4 weeks with dressings and topical steroids. This case of a single isolated congenital mastocytoma shows the broad differential diagnoses that must be considered in the evaluation of bullous lesions in a newborn. It is key to biopsy early and always exclude ­infection.