c-kit Mutation in generalized lentigines associated with gastrointestinal stromal tumor.

We describe the case of a 59-year-old Japanese woman presenting with generalized lentigines without systemic anomalies. She had a medical history of gastrointestinal stromal tumors (GISTs), in which gain-of-function mutations of the c-kit gene had recently been found. We detected a point mutation at codon 557 in exon 11 of leukocyte DNA from the patient. The stem cell factor-type III receptor tyrosine kinase pathway plays important roles in the regulation of melanocyte proliferation and differentiation. We speculate that the generalized lentigines of the patient may be caused by melanocyte proliferation due to the c-kit gene mutation.