Happle‐Tinschert syndrome variable phenotype as part of the mosaic hedgehog spectrum: Report of three cases

Abstract

Happle-Tinschert syndrome is a rare genodermatosis caused by a postzygotic mutation in SMO gene. The most recognized clinical findings include segmentally arranged basaloid follicular hamartomas, nevoid hypertrichosis, linear atrophoderma, and hypopigmentation or hyperpigmentation following Blaschko lines associated with osseous, dental, and cerebral alterations. We report three additional cases, two of which lacked the pathognomonic basaloid follicular hamartomas, with genetic confirmation and detailed clinical characterization and describe new cutaneous features of this infrequent syndrome.

Detection of PTCH1 Copy-Number Variants in Mosaic Basal Cell Nevus Syndrome

“…The development of BCCs, which is one of the major clinical criteria for the diagnosis of BCNS [1], is dependent on a somatic second-hit pathogenic variant in the other PTCH1 allele, which is typically introduced via UV light exposure, causing multiple BCCs to appear at a young age. Additional somatic variants may be introduced in the SHH pathway, for example, in Smoothened (SMO), which may drive BCC development [6].…”