The L1 syndrome may manifest itself as one of several phenotypes. One of these is X-linked complicated corpus callosum agenesis.
Genetic defect: L1CAM (L1 cell adhesion molecule)
Location: Xq28
Inheritance: X-linked (affected males, carrier females)
Features of the complicated corpus callosum agenesis syndrome:
(1) aplasia, hypoplasia or dysplasia of the corpus callosum
(2) mild to moderate intellectual impairment
(3) variable adducted thumb
(4) variable hypotonia and spastic paraplegia (with shuffling gait)
Features of the CRASH syndrome:
(1) corpus callosum hypoplasia (C)
(2) mental retardation (R)
(3) adducted thumbs (A)
(4) spastic paraplegia (S)
(5) hydrocephalus (H)
