Clinical Characteristics

Individuals with MN1 C-Terminal Truncation (MCTT) syndrome have intellectual disability, severe expressive language delay, and dysmorphic facial features such as midface hypoplasia. Affected individuals also have an atypical form of rhombencephalosynapsis (RES), which is a distinctive brain malformation characterized by partial or complete loss of the cerebellar vermis with fusion of the cerebellar hemispheres.