MASA syndrome

MASA syndrome is a rare X-linked neurological disorder whose name is an acronym for its four cardinal features: Mental retardation (intellectual disability), Aphasia (delayed speech), Shuffling gait (spastic paraplegia), and Adducted thumbs. It is caused by mutations in the L1CAM gene located on the X chromosome (Xq28), which encodes the L1 cell adhesion molecule, a protein critical for nervous system development including neuronal migration, axon guidance, and myelination. MASA syndrome is part of a spectrum of L1CAM-associated disorders that also includes X-linked hydrocephalus (HSAS), X-linked complicated hereditary spastic paraplegia type 1 (SPG1), and X-linked agenesis of the corpus callosum. These conditions are collectively referred to as L1 syndrome. The condition primarily affects the central nervous system. Males are predominantly affected, while carrier females are usually asymptomatic or mildly affected. Key clinical features include mild to moderate intellectual disability, delayed speech and language development, lower limb spasticity resulting in a characteristic shuffling gait, and clasped or adducted thumbs due to absence or hypoplasia of the extensor pollicis longus or brevis muscles. Additional features may include hypoplasia or agenesis of the corpus callosum, mild to moderate ventricular enlargement (hydrocephalus), and variable degrees of corticospinal tract dysfunction. Brain MRI may reveal structural abnormalities including corpus callosum anomalies and enlarged ventricles. There is currently no cure for MASA syndrome. Treatment is supportive and multidisciplinary, focusing on managing symptoms and optimizing developmental outcomes. This may include physical therapy and orthopedic interventions for spasticity and gait abnormalities, speech and language therapy, special education services, and occupational therapy. In cases with significant hydrocephalus, neurosurgical intervention such as ventriculoperitoneal shunting may be required. Genetic counseling is important for affected families given the X-linked inheritance pattern.

Common questions about MASA syndrome