Bullous eruption in an infant, what's your diagnosis?

A three-month-old male infant presented with generalized blisters that were first noted when he was two months old. A portion of blisters formed spontaneously and a portion formed when the patient was scratched or rubbed. The lesions were first observed on the hands and feet and spread to the scalp, face and trunk. The infant was otherwise healthy. The mother reported that there was no history of local or systemic symptoms, including flushing, pruritus, shortness of breath, hypotension and diarrhea. Furthermore, the family history was negative for any dermatologic, gastrointestinal or hematologic diseases. Cutaneous examination revealed multiple tense vesicles, bullae, and erosions on the face, scalp, trunk and extremities (Fig. 1). All of the patient’s skin was erythematous and thickened. It had a leathery appearance and a doughy texture, and the skin markings were exaggerated. The patient was positive for Darier’s sign. There was no evidence of organomegaly or lymphadenopathy. Bacterial blister culture results were negative. Direct immunofluorescence was also negative. Histological examination of a biopsy specimen taken from a tense blister revealed sub-epidermal bullae with a dense infiltration of mast cells and a number of eosinophils in the upper dermis (Figs. 2 and 3).