Gorlin-like phenotype in a patient with a PTCH2 variant of uncertain significance

Abstract

Gorlin syndrome, also known as Nevoid Basal-Cell Carcinoma Syndrome (NBCCS), is an autosomal dominant tumor predisposition syndrome that presents early in life with characteristic congenital malformations and tumors. This syndrome most commonly results from germline mutations of the PTCH1 tumor suppressor gene, which shows high penetrance and great intra and interfamilial phenotypic variability, as well as the SUFU tumor suppressor gene. Recently, the PTCH2 gene has also been implicated as a cause of Gorlin syndrome. Notably, these patients displayed milder phenotypes of Gorlin syndrome when considered against PTCH1 and SUFU-related disease. We report a patient with a novel PTCH2 mutation inherited from his father. The proband displays several minor diagnostic features of Gorlin syndrome, supporting the pathogenic role of this gene. Features in the proband include macrocephaly, a wide face, prominent forehead, hypertelorism/telecanthus, large eyes, cleft lip and palate, thin vertical palmar creases, penoscrotal inversion, and a hyperpigmented spot on his penis. His father displays macrocephaly, several nevi on his back and shoulders, and a single palmar pit on his left hand, raising suspicion for Gorlin syndrome. Whole exome sequence (trio) found that the proband and father are heterozygous for NM_003738.4:c.3347C>T;p.(Pro1116Leu) in exon 21 of PTCH2, found also in his mildly affected brother. This semi-conservative amino acid substitution has been reported in the literature, but its significance is unclear. Notably, the proband, brother, and father do not meet clinical criteria for Gorlin syndrome. However, the clinical findings described in this family support the association between PTCH2 mutations and Gorlin-like phenotypes.

Keywords: Gorlin syndrome; Gorlin-like syndrome; Mild phenotype; Nevoid basal cell carcinoma syndrome; Novel PTCH2 variant.