A Cajun kindred with Pelizaeus-Merzbacher disease was found to have a p.Q128X mutation in exon 3B of proteolipid protein 1 (PLP1). The affected males were globally delayed in development, nonambulatory, and severely dysarthric. The heterozygous females developed progressive gait disturbances and cognitive deterioration starting in the fourth decade of life. The average IQ (Stanford-Binet Intelligence Scale: 4th Edition (SBFE)) of the carrier females was 54.2, compared to the average IQ of 97.5 in nonaffected relatives. The X-inactivation ratios in the three carrier females were not markedly skewed (55:45, 70:30, and 85:15). The presence of neurological and cognitive deterioration in the three carriers deviates from the usual expectation that carrier expression only occurs in families when males are mildly affected.
(c) 2007 Wiley-Liss, Inc.