UC Irvine

Purpose

Nevoid Basal Cell Carcinoma Syndrome (NBCCS) is an autosomal-dominant disorder characterized by multiple basal cell carcinomas, jaw cysts, palmar/plantar pits, calcification of the falx cerebri, and spine and rib anomalies. NBCCS is due to mutations in PTCH1, the human homologue of the Drosophila segment polarity gene patched. Mutations are detected in approximately 60% to 85% of individuals tested by sequencing of PTCH1; therefore, clinical examination and x-rays remain important in diagnosis of NBCCS.

Methods

We studied 82 NBCCS patients and 38 of their unaffected siblings at the NIH between 1985 and 1994. Chest, rib, spine, skull, hand and foot x-rays, brain MRI or CT, and pelvic ultrasound (in females) were obtained in the affected individuals and compared to their unaffected relatives.

Results

The following features were significantly more frequent in those with NBCCS: calcification of the falx cerebri, the most frequent radiological feature, was present in 79% of patients > 20 years and in 37% <20 years, calcification of the tentorium cerebellum was present in 20%, bridging of the sella in 68%, and abnormal frontal sinus aeration in 18% of affected individuals. Bifid ribs most often involving the third, fourth, and fifth ribs were seen in 26%; splayed, fused, and misshapen ribs in a further 16%, and widened ends of clavicles in 12%. Spine X-rays revealed calcification of the nuchal ligament in 18%, fusion of vertebrae in 10%, and hemivertebrae in 15%. Flame-shaped lucencies of the metacarpals and/or phalanges were present in 30%, modeling deformities of the phalanges in 14%, and polydactyly of the feet in 4%. The frequency of scoliosis, cervical ribs, absent or rudimentary ribs, spina bifida occulta, or short 4th metacarpal was not higher in the affected individuals as compared to their unaffected relatives. Except for falx calcification, the frequency of radiological manifestations was similar in different age groups. Cranial CT or MRI in 42 affected individuals revealed asymmetric or dilated ventricles in 24%, cerebral atrophy in 10%, cavum septum pellucidum in 19%, dysgenesis or agenesis of the corpus callosum in 10%, and meningioma in 5%. Ovarian fibromas were detected in 17% of females.

Conclusions

This study reports the varied radiological manifestations of NBCCS. In the absence of major features such as basal cell carcinomas, jaw cysts, or falx calcification, which is often not evident until the teen years, other radiological manifestations of the disorder can permit early diagnosis of NBCCS in childhood. This will allow optimum surveillance for medulloblastoma and other neoplasms (cardiac fibromas and basal cell carcinomas) associated with NBCCS.