A kindred of 7 affected male infants with an X-linked mental retardation and epilepsy syndrome (XMRE), distinct from X-linked West and other mental retardation-epilepsy syndromes, is reported from the University of Michigan, Ann Arbor, MI. The locus for the new syndrome is identified on chromosome Xp21.1-p11.4. The tetraspanin gene, implicated in nonspecific mental retardation, was not involved. Seizures were primarily generalized, tonic-clonic, and atonic and began at 4 to 14 months of age (average age, 6.8 months). None had infantile spasms or hypsarrhythmia, and other than mental retardation and epilepsy affecting all patients, and mild rigidity and ataxia in 2, the neurologic examination was unremarkable. MRI, EMG, NCS, and laboratory metabolic tests were normal. 
COMMENT. X-linked mental retardation is clinically heterogeneous and is reported in 25% of all MR. The authors cite references to 202 XLMR genetically mapped syndromes and 33 identified XLMR genes. Seizures occur with several XLMR disorders, and West syndrome is sometimes transmitted as an X-linked disorder mapped to a locus on Xp21.3-Xp22,l, and distinct from the present novel family. In patients without recognizable metabolic or developmental brain abnormalities, a search for X-linked genetic factors is important in XMRE syndromes.