Dystrophin immunocytochemistry was used to study muscle biopsies from 505 girls and women with neuromuscular disease seen at the National Institute of Neuroscience, Tokyo, the University of Pittsburgh School of Medicine and the Columbia Presbyterian Medical Center, New York. The laboratory findings of 25 (54%) of 46 isolated cases with muscle biopsies were consistent with the familial cases and all showed myopathic histopathology and abnormal elevations of serum CK. The clinical presentations of the isolated cases were consistent with familial cases and included proximal limb weakness before age 10 (40%), myalgias or cramps (24%) and grossly elevated CK levels (24%). About 10% of the isolated cases of hyperCKemic myopathy were proven by dystrophin analysis to have a dystrophinopathy as the cause of their disease (manifesting carriers of Duchenne dystrophy). 
COMMENT. All isolated female dystrophinopathy patients had had other diagnoses prior to dystrophin testing, the most common being the limb girdle muscular dystrophy. The clinical criteria that implicate a dystrophinopathy in isolated nonfamilial cases in girls and women include a serum CK level in excess of 1,000 IU/1 and a myopathic histopathology. The exclusion of dystrophinopathy by dystrophin analysis is necessary in confirming a diagnosis of isolated limb girdle muscular dystrophy.
A dystrophin test is also recommended in patients with idiopathic cardiomyopathies since cardiomyopathy was found as the only clinical manifestation in 2 Duchenne muscular dystrophy carriers reported from Rome, Italy . There was no muscle weakness and serum CK was only mildly increased.