Dystrophin analysis in Duchenne and Becker muscular dystrophy carriers: correlation with intracellular calcium and albumin. Immunocytochemical localization and immunoblot analysis of dystrophin in muscle fibers of 11 obligate and probable, and 7 possible carriers of Duchenne and Becker muscular dystrophy revealed an abnormal expression of the protein in 3 of them. Localization of calcium and albumin, as endogenous markers of extracellular fluid penetration, showed the presence of both molecules inside some fibers lacking dystrophin. Our morphological studies show that the initial stages leading to fiber necrosis in Duchenne muscular dystrophy are present in carriers with mosaicism. Comparison of dystrophin studies with restriction fragment length polymorphism analysis and creatine kinase levels showed that neither immunocytochemical nor immunoblot techniques for dystrophin are sensitive enough to provide a basis for genetic counseling. 