[Homologies between membrane proteins result in expected or unexpected relations between neuromuscular and erythrocyte diseases].

The advances achieved in biochemistry and molecular genetics have made it possible to demonstrate that the membrane proteins of the erythrocytes belong to protein "families" that are present in most cell membranes and share remarkable structural and functional homologies. Abnormalities of erythrocyte membrane proteins might then totally or partially reflect lesions of other cell membranes that are intrinsically more severe than those of the erythrocytes. Examples of these physiopathogenetic links can be found in congenital diseases where muscular and erythrocytic pathologies coexist. Such are: (1) choreaacanthocytosis supported by molecular abnormalities of the so-called band 3 protein or anion channel; (2) Mac Leod syndrome by deficiency of a membrane protein precursor of Kell antigens; (3) some cases of hereditary spherocytosis associated with qualitative and quantitative ankyrin alterations. Yet, despite the homologies that are known to exist between spectrin and dystrophin, all attempts to use spectrin analysis as marker of Duchenne-Becker muscular dystrophy have met with complete failure, which shows that at this early stage one should refrain from drawing firm physiopathological conclusions from the available data.