Muscular Dystrophy, Limb-Girdle, Autosomal Recessive 5

A number sign (#) is used with this entry because autosomal recessive limb-girdle muscular dystrophy-5 (LGMDR5) is caused by homozygous mutation in the gamma-sarcoglycan gene (SGCG; 608896) on chromosome 13q12.

For a discussion of genetic heterogeneity of autosomal recessive LGMD, see LGMDR1 (253600).

Nomenclature

At the 229th ENMC international workshop, Straub et al. (2018) reviewed, reclassified, and/or renamed forms of LGMD. The proposed naming formula was 'LGMD, inheritance (R or D), order of discovery (number), affected protein.' Under this formula, LGMD2C was renamed LGMDR5.

Clinical Features

Autosomal recessive inheritance of a muscular dystrophy resembling X-linked Duchenne muscular dystrophy (DMD; 310200) was reported by Kloepfer and Talley (1958), Dubowitz (1960), and Skyring and McKusick (1961), among others. The clinical course was characterized by onset before age 5 years, confinement to wheelchair by 12 years, and death usually before age 20 years. Pseudohypertrophy was present. Skyring and McKusick (1961) suggested that the signs of cardiac involvement present in the X-linked form may be lacking in the autosomal variety.

McKusick (1971) had the opportunity to restudy 2 affected sibs reported by Kloepfer and Talley (1958). At that time, the 30-year-old sister had evidence of cardiac involvement with chronic congestive heart failure, and the 27-year-old brother had arrhythmia with coronary sinus rhythm by electrocardiogram. The sister had 2 children, aged 6 and 4 years.

Ben Hamida et al. (1983) reported 93 children with a form of autosomal recessive, severe, progressive muscular dystrophy unusually frequent in Tunisia. Of the 93 cases, 75 came from 17 families with affected persons of both sexes and the other 18 came from 11 families with only girls affected. The 28 kindreds included 45 pairs of parents with myopathic children. Over three-fourths of the parental pairs were closely consanguineous, compared with consanguinity rates of 16 to 23% in the general population. Inability to walk occurred between ages 10 and 20. The serum creatine kinase was markedly raised in the early stages of disease. Muscle wasting affected mainly limb girdle and truncal muscles; calf muscle hypertrophy was usually present.

Somer et al. (1985) reported 2 sisters with severe muscular dystrophy from a family of 12 sibs with consanguineous parents. Muscle weakness began at ages 7 and 6 years, respectively. The symptoms progressed rapidly and the patients were confined to wheelchairs at ages 12 and 11 years, respectively. They both had mild facial weakness and pseudohypertrophy of the calves, but neither had cardiomyopathy or mental retardation. Serum creatine kinase levels exceeded upper normal limits by 70- to 85-fold. Both girls had a normal karyotype, and the clinical picture was indistinguishable from that of the X-linked form.

Merlini et al. (2000) reported clinical homogeneity among the Romany Gypsies in western Europe with LGMD2C. All shared a common founder mutation (608896.0002). Mean age at onset was 5.3 years. One-half of the patients lost ambulation by the age of 12; 13% could still walk after age 16. Calf hypertrophy, scapular winging, macroglossia, and lumbar lordosis were common. Girdle, trunk, and proximal limb muscles had earlier and more severe involvement. Cardiomyopathy was not observed.

In a study of 10 Gypsy patients with LGMD2C, Calvo et al. (2000) found evidence of subclinical cardiac involvement. Electrocardiographic and echocardiographic evaluation indicated mild right ventricular dysfunction.

Other Features

Duchenne muscular dystrophy is caused by mutation in the dystrophin gene (300377) on the X chromosome. Dystrophin is associated with a large oligomeric complex of sarcolemmal glycoproteins, the dystrophin-glycoprotein complex, which spans the sarcolemma to provide a link between the subsarcolemmal cytoskeleton and the extracellular matrix component, laminin (150320). In DMD, the absence of dystrophin leads to a large reduction in all of the dystrophin-associated proteins (Matsumura et al., 1992). Ben Jelloun-Dellagi et al. (1990) demonstrated that the dystrophin protein is normal in the Tunisian form of autosomal recessive muscular dystrophy.

Vainzof et al. (1991) described a 7.5-year-old boy, born of consanguineous parents, with typical symptoms and clinical findings of DMD including hypertrophy of the calves, Gowers sign, and lordosis. Normal dystrophin immunostaining and the lack of DNA deletion with dystrophin probes excluded a diagnosis of X-linked DMD. The presence of normal dystrophin was confirmed by the concomitant use of 2 antibodies, one against the C-terminal region and one against the N-terminal region in Western blot analysis.

In patients with SCARMD, Matsumura et al. (1992) demonstrated deficiency in the 50-kD subunit of the dystrophin-associated glycoprotein (DAG2 or DAG50), also referred to as adhalin or alpha-sarcoglycan (SGCA; 600119). The authors concluded that the loss of adhalin is a common denominator of the pathologic process in DMD and SCARMD. El Kerch et al. (1994) found absence of DAG50 in a muscle biopsy from a patient with SCARMD. No abnormality of this protein was found in a variety of other neuromuscular disorders. Higuchi et al. (1994) noted that alpha-sarcoglycan deficiency had been demonstrated in 1 Greek, 1 Italian, 3 French (Fardeau et al., 1993), and 5 Brazilian (Passos-Bueno et al., 1993) patients with severe muscular dystrophy. They reported for the first time 2 Japanese patients with adhalin deficiency. In addition, they demonstrated abnormal expression of laminin in the basal lamina surrounding muscle fibers, which implicated a disturbance of sarcolemma-extracellular matrix interaction in the molecular pathogenesis of muscle fiber necrosis in these patients. Piccolo et al. (1995) noted that there are 2 kinds of myopathies with adhalin deficiency: one with a primary defect of adhalin (LGMDR3; 608099) caused by mutation in the SGCA gene, and those such as SCARMD in which absence of adhalin is secondary to mutation in another gene.

Jung et al. (1996) produced specific antibodies against a gamma-sarcoglycan peptide and used them to examine the expression of this protein in skeletal muscle of patients with SCARMD. Immunofluorescence and Western blotting in skeletal muscle from these patients showed complete absence of gamma-sarcoglycan. Alpha- and beta-sarcoglycan were also greatly reduced, whereas other components of the dystrophin-glycoprotein complex were preserved. In addition, they showed that in normal muscle alpha-, beta-, and gamma-sarcoglycan constituted a tightly associated sarcolemmal complex that could not be disrupted by SDS treatment.

Inheritance

In 3 young girls, Hazama et al. (1979) reported autosomal recessive inheritance of progressive muscular dystrophy.

Goonewardena et al. (1988) used DNA probes to exclude linkage to the X chromosome in 2 brothers with muscular dystrophy. The authors suggested autosomal recessive inheritance of the disorder.

Mapping

Linkage studies by Ben Othmane et al. (1992) using 3 consanguineous families from Tunisia demonstrated that the DMD-like disease locus was situated on chromosome 13p; 2 markers within 13q12 showed a lod score of 9.15 and 8.4 at theta = 0.03. In affected Algerian families, Azibi et al. (1993) confirmed the assignment of the mutant gene to proximal 13q. They identified 57 Algerian patients with the disorder, which they referred to as 'severe childhood autosomal recessive muscular dystrophy' (SCARMD). The patients belonged to 34 families, of which 29 had more than 1 affected member.

El Kerch et al. (1994) found linkage homogeneity to 13q in affected patients from Morocco, Tunisia, and Algeria, 3 Maghreb countries with a high frequency of the disorder. Ben Othmane et al. (1995) found that 6 Tunisian families and 1 Egyptian family with DMD-like muscular dystrophy showed linkage to the pericentromeric region of chromosome 13q (maximum lod score of 9.15 at D13S115). The authors stated that the Egyptian family was the first non-North African family to be linked to the 13q locus.

Exclusion Mapping

Francke et al. (1989) described 2 families in which a brother and sister were affected with early-onset progressive muscular dystrophy. The dystrophin gene did not appear to be involved in either family. In 1 family, the affected male was found to share the complete dystrophin RFLP haplotype with his unaffected brother, while his affected sister had inherited the other maternal haplotype. In the second family, no deletion of the DMD gene was detected in the affected male who shared a complete Xp21 haplotype with an unaffected sister, while the affected sister had inherited a recombinant Xp21 region. X-inactivation studies showed random inactivation in the affected girl's leukocytes. In a muscle biopsy from the affected male, the dystrophin protein was present in normal amount and size.

Azibi et al. (1991) excluded linkage to the 6q22-q23 region that includes the dystrophin-related protein (128240) in 19 Algerian families with autosomal recessive DMD-like muscular dystrophy.

In a study of 4 Brazilian families with severe childhood autosomal recessive Duchenne-like muscular dystrophy, Passos-Bueno et al. (1993) excluded linkage to markers on 15q which are associated with LGMD2A (LGMDR1; 253600), a milder form of autosomal recessive LGMD with later onset.

Molecular Genetics

In 2 affected sibs from a Tunisian SCARMD family reported by Ben Othmane et al. (1992), Noguchi et al. (1995) identified a homozygous mutation in the SGCG gene (608896.0001). The authors noted that the mutation not only affects gamma-sarcoglycan, but also disrupt the integrity of the entire sarcoglycan complex.

In 4 of 50 muscular dystrophy patients from the U.S. and Italy, McNally et al. (1996) identified 4 homozygous mutations in the SGCG gene (e.g., 608896.0003; 608896.0004; 608896.0006). They predicted that all 4 mutations lead to disruption of the reading frame of the protein. Microdeletions that disrupted the distal C terminus of gamma-sarcoglycan were identified in 2 of the 4 patients. These distal C-terminal deletions resulted in complete absence of gamma- and beta-sarcoglycan. McNally et al. (1996) concluded that this region is important for the stability of the sarcoglycan complex. The 4 patients were partially deficient for alpha-sarcoglycan immunostaining. The authors suggested that a gamma-sarcoglycan antibody should also be used when initially evaluating patients with muscular dystrophy.

Piccolo et al. (1996) identified homozygosity for a mutation (608896.0002) in the SGCG gene in 18 patients with LGMD2C from 7 large LGMD2C Gypsy families who had lived in France, Italy, and Spain for several generations. All affected chromosomes in homozygous and heterozygous relatives carried the same allele ('allele 5') of the intragenic marker D13S232. Piccolo et al. (1996) also delineated a common ancestral haplotype.

Leal and Da-Silva (1999) reported a clinical and molecular analysis of a 5-generation Brazilian family with LGMD2C. Clinical severity varied according to sex, with males having significantly earlier onset of symptoms and age of confinement to a wheelchair. Mutation analysis confirmed that affected individuals had a mutation in the SGCG gene (608896.0001).

Trabelsi et al. (2008) identified biallelic mutations in sarcoglycan genes in 46 (67%) of 69 patients with a clinical diagnosis of autosomal recessive LGMD. Twenty-six (56.5%) patients had SGCA mutations, 8 (17.3%) had SGCB (600900) mutations, and 12 (26%) had SGCG mutations. Five of the 10 SGCG mutations identified were novel.

Population Genetics

Zatz et al. (1989) studied 470 families in which X-linked inheritance of muscular dystrophy could not be confirmed: 20 with at least 1 affected girl with a Duchenne-like phenotype and 450 with only affected boys. Based on the number of families with at least 1 affected girl and the number of patients per sibship in these pedigrees, the proportion of families with DMD inherited as an autosomal recessive trait was estimated at 6.8%. It was also estimated that 2.5 to 4% of isolated male cases of DMD may have the autosomal recessive form.

By analysis of dystrophin in 50 males diagnosed with DMD, Vainzof et al. (1991) estimated that the frequency of autosomal recessive muscular dystrophy may be 8 to 12% among male patients diagnosed with DMD in whom X-linked inheritance could not be definitively established.

Stec et al. (1995) examined a total of 415 families with at least 1 living male patient with clinical features suggesting Duchenne muscular dystrophy. Based on formal genetics, haplotype analysis, and dystrophin determinations, they estimated that 1 in 8 (11.8%) sporadic male patients suffer from an autosomal rather than an X-chromosomal mutation, most often LGMD2C or LGMD2D (LGMDR3; 608099).

Hayashi et al. (1995) performed an immunocytochemical survey of muscle biopsies from 243 Japanese muscular dystrophy patients over 2.5 years. They identified 5 unrelated Japanese patients with adhalin deficiency manifesting as an extremely faint but positive staining of the sarcolemma similar to that described in the 13q-linked congenital muscular dystrophy prevalent in North Africa. From these data, they predicted the gene frequency for this deficiency in Japan to be between 0.1 and 0.2%, with a prevalence of the deficiency in the Japanese population to be about 1 x 10(-6). In their series, Hayashi et al. (1995) found this deficiency to account for only 4% of patients with DMD/BMD.

Piccolo et al. (1996) identified the C283Y SGCG mutation (608896.0002) as a founder mutation in the Romany Gypsies of Europe, who are believed to have originated from northern Indian populations that arrived in Europe around 1100 A.D. Due to almost complete endogamy, they formed a genetically isolated community. By haplotype analysis, Piccolo et al. (1996) estimated that the C283Y mutation is at least 1,200 years old and predates the migration of the Gypsies out of northern India.

Navarro and Teijeira (2003) provided a detailed review of neuromuscular disorders among the Romany Gypsies.

History

Azibi (1991) referred to this disorder as Maghrebian autosomal recessive myopathy. The Maghreb, meaning 'west' in Arabic, represents the area of North Africa and particularly the coastal plain of Morocco, Algeria, Tunisia and Libya. It was referred to as Africa Minor in ancient times and at one time included Moorish Spain.

Animal Model

Mice lacking gamma-sarcoglycan develop progressive muscular dystrophy similar to human muscular dystrophy. Without gamma-sarcoglycan, beta- and delta-sarcoglycan (601411) are unstable at the muscle membrane and alpha-sarcoglycan is severely reduced. The expression and localization of dystrophin, dystroglycan, and laminin-alpha-2 (156225), a mechanical link between the actin cytoskeleton and the extracellular matrix, appear to be unaffected by the loss of sarcoglycan. Hack et al. (1999) assessed the functional integrity of this mechanical link and found that isolated muscles lacking gamma-sarcoglycan showed normal resistance to mechanical strain induced by eccentric muscle contraction. Sarcoglycan-deficient muscles also showed normal peak isometric and tetanic force generation. Furthermore, there was no evidence for contraction-induced injury in mice lacking gamma-sarcoglycan when they were subjected to an extended, rigorous exercise regimen. These findings demonstrated that mechanical weakness and contraction-induced muscle injury are not required for muscle degeneration and the dystrophic process. Thus, Hack et al. (1999) concluded that a nonmechanical mechanism, perhaps involving some unknown signaling function, is likely to be involved in cases of muscular dystrophy in which sarcoglycan is deficient.

In a review, Shelton and Engvall (2005) stated that canine models of sarcoglycanopathies had been reported in the Boston terrier, Cocker spaniel, and Chihuahua breeds. Although specific mutations in sarcoglycan genes had not yet been characterized, all 3 models showed absence of gamma-sarcoglycan in muscle tissue.