Gorlin-Goltz syndrome is a rare autosomal dominant disorder characterized by multiple basal cell carcinomas (BCCs), odontogenic keratocysts of the jaws, and other systemic manifestations. In a three-generation family, a heterozygous PTCH1 splice site mutation (NM000264.5:c.3449 + 1G > A) was inherited with the disease. A minigene splicing assay demonstrated skipping of exon 20, leading to loss of gene function. Two patients with multiple BCCs received sonidegib orally for 6 months: one 200 mg daily, the other 200 mg every other day. Both showed clinical regression of BCC lesions. Dysgeusia and alopecia occurred with daily dosing, while every-other-day dosing was well tolerated. The case confirms the importance of transcript-level functional assays for PTCH1 variants and supports individualized dosing of sonidegib according to toxicity.