A Case of Lateral Meningocele Syndrome without Lateral Meningoceles

Lateral meningocele syndrome (LMS), also known as Lehman syndrome, is caused by pathogenic variants in exon 33 of NOTCH3. Variants in this final exon of NOTCH3 interrupt the regulatory PEST domain, leading to enhanced NOTCH3 signaling due to prolonged cellular half-life. Individuals with LMS are expected to have multiple lateral meningoceles, developmental delay, neonatal hypotonia, dysmorphic facial features, and feeding difficulties.

We report an 8-year-old male with a history of autism, feeding difficulties, developmental delay, severe intellectual disability, and self-injurious behavior. Genetic testing revealed a NOTCH3 c.6663C>G (p.Y2221*) pathogenic variant in exon 33, consistent with a diagnosis of LMS. A follow-up spine MRI showed a ventral sacral extradural arachnoid cyst but no lateral meningoceles. This individual's most recent exam noted multiple dysmorphic features including prominent metopic ridging, broad forehead, downslanting palpebral fissures, high-arched palate, long narrow philtrum, mild pectus excavatum, and wide-based gait.

This individual shares the dysmorphic facial features, ongoing G-tube dependence, failure to thrive, and developmental delay seen in other individuals with LMS. His lack of lateral meningoceles expands the phenotype for this condition, as all previously reported individuals with molecularly confirmed LMS had multiple lateral meningoceles before age 8 years with an average age of identification at 4 years.