**2. Risk factors**

There are no known risk factors for GIST. Though most of GISTs are sporadic, the minority occur as part of hereditary syndrome.

Familial GIST syndrome: several family members with hereditary mutations in either the KIR or PDGFRA genes have been reported in the study [19–28]. These families have a higher risk to develop multiple gastric and small bowel GISTs. Some patients may have skin hyperpigmentation, dysphagia, gastrointestinal autonomic nerve tumors, intestinal fibromatosis, and inflammatory fibroid polyps [19–28].

Carney-Stratakis syndrome is an autosomal-dominant disease which is characterized by dyad of multifocal GISTs and paragangliomas [29]. Patients do not have KIT or PDGFRA mutations, but do have mutations of succinate dehydrogenase subunits (SDH) A, B, C, or D [30].

Carney's triad: a very rare non-heritable syndrome characterized by gastric GIST, paraganglioma and pulmonary chondromas. These patients are characterized by mutations succinate dehydrogenase subunit (SDH) C [29] but lack mutations of KIT and PDGFRA.

Neurofibromatosis type 1: patients with NF1 are more predisposed for multifocal GISTs that mainly affect the small intestine [31].
