Neurofibromatosis 1 (NF1) is a hereditary monogenic disorder. Common symptoms are cafe au lait spots and / or axillary or inguinal freckles, and cutaneous neurofibromas. In a recent population-based study the cancer risk of NF1 patients was twice compared to average population. This is a case report of patients with variable disease in three generations with GIST and various neuropsychologic symptoms in family, and in which the pathogenic NF1 variant was identified first at the RNA level and then at the DNA level. The case report confirms that GIST tumor is a universal symptom in different NF1 PVs and good academic skills can be achieved even if neuropsychological symptoms are challenging.