Basal cell nevus syndrome or Gorlin syndrome.

Basal cell nevus syndrome (BCNS) or Gorlin syndrome is a rare neurocutaneous syndrome sometimes known as the fifth phacomatosis, inherited in autosomal dominant fashion with complete penetrance and variable expressivity. Gorlin syndrome is characterized by development of multiple basal cell carcinomas (BCCs), jaw cysts, palmar or plantar pits, calcification of falx cerebri, various developmental skeletal abnormalities such as bifid rib, hemi- or bifid vertebra and predisposition to the development of various tumors. BCNS is caused by a mutation in the PTCH1 gene localized to 9q22.3. Its estimated prevalence varies between 1/55600 and 1/256000 with an equal male to female ratio. The medulloblastoma variant seen in Gorlin syndrome patients is of the desmoplastic type, characteristically presenting during the first 3 years of life. Therefore, children with desmoplastic medulloblastoma should be carefully screened for other features of BCNS. Radiation therapy for desmoplastic medulloblastoma should be avoided in BCNS patients as it may induce development of invasive BCCs and other tumors in the skin area exposed to radiation. This syndrome is a multisystem disorder so involvement of multiple specialists with a multimodal approach to detect and treat various manifestations at early stages will reduce the long-term sequelae and severity of the condition. Life expectancy is not significantly altered but morbidity from complications and cosmetic scarring can be substantial.