A mutation in either BRAF (7q34), MAP2K1 (15q22.1-q22.33),MAP2K2 (19p13.3), or KRAS (12p12.1) causes this disease. A mutation in the formermost gene is the cause for 75% of the cases of this disease. (Orphanet) Although the possibility of inheritance of this gene is theoretically 50%, few cases of families with these mutated genes have been reported. Thus, this rare disease is usually caused by the mutation of the gene in the patient him/her-self. There may be genes responsible for the disease other than the four listed here, as there have been patients diagnosed with this disease in which these four genes were all healthy. (NORD)

 

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