Cutaneous hyperpigmentation and familial gastrointestinal stromal tumour associated with KIT mutation

Summary Gastrointestinal stromal tumours (GISTs) are mesenchymal tumours arising in the gastrointestinal tract. Early detection, before metastasis occurs, is important as complete surgical excision achieves cure. Approximately 85% of GISTs are associated with mutations in the KIT gene, and although the majority of GISTs are sporadic, familial GISTs have been identified. Several families with multiple GIST tumours have also been described with various cutaneous findings including hyperpigmentation, multiple lentigines, vitiligo and urticaria pigmentosa. We discuss a 6‐year‐old boy who presented with an unusual pattern of hyperpigmentation in association with a family history of GIST. A causative KIT mutation was identified in DNA from the pigmented skin and from the resected GIST, and the patient was referred to the Paediatric Gastroenterology department for GIST screening. The term ‘GIST cutaneous hyperpigmentation disease’ has been suggested previously for the association of familial GIST with cutaneous hyperpigmentation caused by a germline KIT mutation.