A Rett syndrome MECP2 mutation that causes mental retardation in men

Objective: To characterize the clinical features of a new type of X-linked mental retardation associated with MECP2 mutation in the index family. Background: MECP2 mutations, originally described in a high percentage of patients with classic Rett syndrome, were considered lethal in men. The authors recently described a novel A140V MECP2 missense mutation in an Italian family with X-linked semidominant mental retardation. Methods: The neurologic features of six symptomatic relatives (two women and four men) carrying the mutation were compiled. Laboratory investigations included EEG, EMG, conduction velocity (CV) of peripheral nerves, brain MRI, and ¹H-MR spectroscopy. Results: Mental retardation and signs of neurologic impairment were present in all the affected members, but more pronounced in men. Neurologic features included slowly progressive spastic paraparesis/pyramidal signs (6/6), distal atrophy of the legs (6/6), ataxia (2/6), and postural tremor of the hands (3/6). Speech was preserved (6/6) but was dysarthric in the oldest brothers (2/6). Mild dysmorphic features were present in all cases. Conclusion: The neurologic disorder associated with A140V MECP2 mutation is not necessarily lethal in men, but they are more severely affected than women of the same family.