X-LINKED HYDROCEPHALUS AND MASA SYNDROME

X linked hydrocephalus and MASA syndrome are clinically related, neuro logical disorders with an X linked recessive mode of inheritance. Alth ough originally described as distinct entities, their similarity has b ecome apparent as the number of reported families has increased and a high degree of intra- and interfamilial variation in clinical signs no ted for both disorders. Consideration of this clinical overlap togethe r with finding that genes for both diseases map to the same chromosoma l band (Xq28) led to the hypothesis that they were caused by mutation at the same locus. This was confirmed by identification of mutations i n patients with X linked hydrocephalus and MASA syndrome within the ge ne for neural cell adhesion molecule L1. Here we review the clinical a nd genetic characteristics of these disorders and the underlying molec ular defects in the L1 gene.