Progress in the Molecular Diagnosis of Facioscapulohumeral Muscular Dystrophy and Correlation Between the Number of KpnI Repeats at the 4q35 Locus and Clinical Phenotype

Ann Neurol. 1999 Jun;45(6):751-7. doi: 10.1002/1531-8249(199906)45:6<751::aid-ana9>3.0.co;2-m.

Abstract

Genotype analysis by using the p13E-11 probe and other 4q35 polymorphic markers was performed in 122 Italian facioscapulohumeral muscular dystrophy families and 230 normal controls. EcoRI-BlnI double digestion was routinely used to avoid the interference of small EcoRI fragments of 10qter origin that were found in 15% of the controls. An EcoRI fragment ranging between 10 and 28 kb that was resistant to BlnI digestion was detected in 114 of 122 families (93%) comprising 76 familial and 38 isolated cases. Among the unaffected individuals, 3 were somatic mosaics and 7, carrying an EcoRI fragment larger than 20 kb, could be rated as nonpenetrant gene carriers. In a cohort of 165 patients with facioscapulohumeral muscular dystrophy we found an inverse correlation between fragment size and clinical severity. A severe lower limb involvement was observed in 100% of patients with an EcoRI fragment size of 10 to 13 kb (1-2 KpnI repeats left), in 53% of patients with a fragment size of 16 to 20 kb (3-4 KpnI repeats left), and in 19% of patients with a fragment size larger than 21 kb (>4 KpnI repeats left). Our results confirm that the size of the fragment is a major factor in determining the facioscapulohumeral muscular dystrophy phenotype and that it has an impact on clinical prognosis and genetic counseling of the disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Chromosomes, Human, Pair 4 / genetics*
  • Humans
  • Muscular Dystrophies / genetics*
  • Muscular Dystrophies / physiopathology
  • Pedigree
  • Phenotype
  • Prognosis
  • Risk Factors
  • Tandem Repeat Sequences

Grant support