Four of 8 definite heterozygous female carriers determined by PCR amplification of tandem
CAG repeat of the AR gene, from 4 families of X-linked recessive bulbospinal neuronopathy
(X-BSNP) showed extensive high amplitude motor unit potentials in examined muscles
although all subjects were neurologically normal. Plasma creatine kinase, myoglobin,
myosin light chain, lactate and pyruvate were all normal even in the carriers who showed
EMG abnormalities. Muscle biopsy showed a type 2 fiber preponderance and possible very …