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Imatinib for control of bullous skin lesions in a child with familial mastocytosis

A 16-month-old boy, with a family history of systemic mastocytosis due to a familial KIT K590I mutation was referred to the haematology clinic with widespread bullous eruptions and pruritus that had been occurring since 3 months of age. Darier sign was positive. He had had frequent severe exacerbations unresponsive to several antihistamines. Physical examination showed multiple maculopapular bullous exanthematous lesions (left). A familial KIT K590I mutation was demonstrated by direct sequence analysis and baseline investigations showed an unrecordably high (>99 0 ng/ml) serum tryptase (normal range 2 0–11 4 ng/ml). This particular familial mutation is known to be exquisitely sensitive to tyrosine kinase inhibition. He commenced imatinib, which led to resolution of skin lesions (right), normalisation of serum tryptase and, importantly, control of his symptoms. His condition remains improved at follow-up at 10 months with normal growth and development, and no adverse drug effects. This case highlights the important role of tyrosine kinase inhibitors in disease control in familial mastocytosis with specific KIT mutations.