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Rippling muscle disease: evidence for phenotypic and genetic heterogeneity
1Department of Neurology, Room A 343, Stanford University Medical Center, Stanford, California 94305-5235, USA. ytso@Stanford.edu
Abstract:
We describe the clinical features of a family with rippling muscle disease. Muscle stiffness and myalgia were the most prominent symptoms. Muscle rippling, although distinctive, was present in only 6 of the 11 affected family members, whereas persistent muscle contraction to muscle percussion was present in all affected adults. Although this persistent contraction resembled percussion myotonia, it was electrically silent and is therefore more aptly called "percussion contracture." We also observed two clinical features not emphasized in previously reported kindreds: mild but asymptomatic weakness of face or proximal muscles was present in 5 of 11 affected members, and 5 individuals also complained of toe walking after a prolonged period of inactivity, reflecting the disproportionate involvement of the calf muscles. The pedigree suggested autosomal dominant inheritance. Our linkage analysis excluded the region on chromosome 1q identified in a previous linkage study.
Insights
Rippling muscle disease presents with muscle stiffness and myalgia. Distinctive muscle rippling occurred in some, while all affected adults showed silent "percussion contracture," suggesting autosomal dominant inheritance.
Area of Science:
- Neurology
- Genetics
- Clinical Medicine
Background:
- Rippling muscle disease (RMD) is a rare neuromuscular disorder characterized by muscle hyperexcitability.
- Previous studies have suggested genetic linkage to chromosome 1q.
Observation:
- This study details the clinical presentation in a family with RMD, noting prominent muscle stiffness and myalgia.
- Muscle rippling was observed in 6 of 11 affected individuals.
- Persistent, electrically silent muscle contraction upon percussion, termed 'percussion contracture,' was present in all affected adults.
Findings:
- Two previously underemphasized clinical features were noted: asymptomatic facial/proximal muscle weakness and toe walking after inactivity, indicative of calf muscle involvement.
- The family pedigree indicated autosomal dominant inheritance.
- Linkage analysis excluded the previously implicated 1q region.
Implications:
- These findings expand the known clinical spectrum of rippling muscle disease.
- The exclusion of the 1q region suggests alternative genetic loci for RMD.
- Further genetic studies are warranted to identify the causative gene(s) for RMD.