Systematic use of dystrophin testing in muscle biopsies: results in 201 cases

We studied dystrophin with both immunohistochemistry and immunoblotting in 201 muscle biopsies stored in liquid nitrogen during the period 1985-92. The systematic use of dystrophin testing combined with DNA analysis and with 3-10 years follow-up of the patients yielded a significant modification of the diagnoses made previously and identified dystrophinopathies with unusual expression and course. Seventeen out of 152 (11.18%) diagnoses in males and 8 out of 49 (16.32%) in females were modified by dystrophin testing. Most diagnostic errors (9 out of 27 diagnoses) were in the group Becker muscular dystrophy-limb girdle muscular dystrophy, confirming the clinical overlap of the two diseases. Unusual expressions of dystrophinopathy included muscular dystrophy with early elbow contractures (two patients), recurrent myoglobinuria (one patient), dilating cardiomyopathy (two patients), myoglobinuria and associated dilating cardiomyopathy (one patient), very late-onset benign myopathy (two patients and one manifesting carrier) and congenital myopathy (one manifesting carrier). In the group 'idiopathic hyper-CKaemia', we did not find any dystrophinopathy in 34 males, whereas five out of nine females were found to be carriers. Immunohistochemical analysis of dystrophin using the monoclonal antibody against the C-terminus detected 99% of protein defects and was found to be the most cost-effective way of revealing dystrophinopathies. The combined use of immunohistochemical analysis with the antibody against the C-terminus and immunoblotting with the antibody against the core of the protein appears to be a highly reliable diagnostic approach (100% detection rate).