ABSTRACT
FSHD Facioscapulohumeral Muscular Dystrophy: Clinical Medicine and Molecular Cell Biology, edited by Meena Upadhyaya and David N.Cooper. © 2004 Garland/BIOS Scientific Publishers Limited, Abingdon.
17.1 Introduction
Facioscapulohumeral muscular dystrophy (FSHD) is a unique genetic disease in that its molecular aetiology involves a shortening of an array of large tandem repeats on only one homologue at the disease-associated locus. This locus lies within the subtelomeric region of the long arm of chromosome 4 (Chr4), and the repeat is a 3.3 kb sequence termed D4Z4. Although the immediate genetic defect in FSHD has been identified, the way in which it causes the characteristic type of muscular dysfunction (Lunt, 2000) is still mysterious. In almost all FSHD patients there are between one and ten tandem copies of the D4Z4 repeat at the 4q35 band of one Chr4 homologue (Lemmers et al., 2001). By contrast, unaffected individuals have 11-100 copies of this copy-number polymorphic repeat on both Chr4 homologues.
