Phenotypic variability associated with Arg26Gln mutation in caveolin3

Caveolin3 (CAV3) is a protein associated with dystrophin, dystrophin-associated glycoproteins, and dysferlin. Mutations in the CAV3 gene result in certain autosomal-dominant inherited diseases, namely, rippling muscle disease (RMD), limb-girdle muscular dystrophy type 1C (LGMD1C), distal myopathy, and hyperCKemia. In this report we show that a previously reported family with RMD has a mutation in the CAV3 gene. Affected individuals had either a characteristic RMD phenotype, a combination of RMD and LGMD1C phenotypes, or a LGMD1C phenotype, but one mutation carrier was asymptomatic at age 86 years. This phenotypic variability associated with mutations in CAV3 has been reported previously but only in a few families. It is important to remember the significant phenotypic variability associated with CAV3 mutations when counseling families with these mutations. These observations also suggest the presence of factors independent of the CAV3 gene locus that modify phenotype.     

Novel missense mutation in the caveolin-3 gene in a Belgian family with rippling muscle disease

Rippling muscle disease (RMD) is a rare muscle disorder characterised by muscle stiffness, exercise induced myalgia, and cramp-like sensations. It is genetically heterogeneous and can be acquired, but most cases show autosomal dominant inheritance due to mutations in the caveolin-3 (CAV3) gene. We report a novel heterozygous missense mutation in CAV3 in a Belgian family with autosomal dominant RMD. A 40 year old woman complained of fatigue, exercise induced muscle pain, and muscle cramps since the age of 35. Neurological examination revealed percussion induced rapid muscle contractions (PIRCs) and localised muscle mounding on percussion; muscle rippling was not observed. Creatine kinase (CK) was elevated but electromyography and nerve conduction studies were normal. Fluorescence immunohistochemistry revealed reduced caveolin-3 and dysferlin staining in a quadriceps muscle biopsy. Western blot analysis confirmed severely reduced caveolin-3 levels, whereas dysferlin was normal. Sequence analysis of the two coding exons of CAV3 revealed a hitherto unreported heterozygous C82A transversion in the first exon, predicting a Pro28Thr amino acid exchange. Thr patient's first degree relatives did not present with neuromuscular complaints, but PIRCs, muscle mounding, and muscle rippling were found in the mother, who also carried the CAV3 mutation.     

Early-onset toe walking in rippling muscle disease due to a new caveolin-3 gene mutation

The authors describe a family with autosomal dominant rippling muscle disease (RMD) and prominent early-onset toe walking. Molecular analysis revealed a novel heterozygous G > A transition at nucleotide position 136 in exon 2 of the caveolin-3 gene (CAV3). The role of Achilles tendon lengthening in more severe forms of RMD is discussed.     

A sporadic case of rippling muscle disease caused by a de novo caveolin-3 mutation.

OBJECTIVE: To determine the cause of sporadic rippling muscle disease (RMD) in a 24-year-old patient. BACKGROUND: RMD is a rare myopathy characterized by percussion-induced rapid muscle contractions (PIRC), muscle mounding, and rippling waves. We have recently found that autosomal dominant RMD is caused by mutations in the caveolin-3 gene (CAV3) on chromosome 3p25. Possibly, increased activity of neuronal nitric oxide synthase (nNOS) contributes to the clinical characteristics of increased mechanical muscle hyperexcitability. METHODS: Clinical examination, mutational analysis, and immunohistochemistry of muscle tissue were performed in a patient with sporadic RMD. RESULTS: The authors observed a de novo CAV3 missense mutation Arg26Gln. Immunohistochemistry showed reduced caveolin-3 surface expression in a muscle biopsy. In addition, the authors found normal sarcolemmal nNOS expression and a reduced expression of alpha-dystroglycan in muscle fibers. CONCLUSIONS: These data confirm that RMD is caused by CAV3 mutations. Moreover, there is evidence that CAV3 mutations may also be found in patients without a positive family history of RMD.     

Caveolin-3 gene mutation in Japanese with rippling muscle disease

OBJECTIVES: Rippling muscle disease (RMD) is a rare myopathy characterized by percussion-induced rapid muscle contractions, muscle mounding, and rippling. Recently a caveolin-3 gene (CAV3) mutation was identified in patients with autosomal dominant RMD. The objective of this study was to determine whether a similar mutation was present in two Japanese families with this condition. PATIENTS AND METHODS: Clinical examination, mutational analysis, and muscle immunohistochemistry were carried out in six patients from two Japanese RMD pedigrees. RESULTS: Apart from the atrophy of the intrinsic muscles in their hands and a slight muscle weakness in their fingers, the clinical features of our patients were compatible with RMD. Our investigation revealed a CAV3 missense mutation, i.e. Arg26Gln in both families. Immunohistochemistry performed on a muscle biopsy specimen showed reduced caveolin-3 surface expression. CONCLUSIONS: Japanese RMD also appears to result from a CAV3 mutation.     

Mutation in the CAV3 gene causes partial caveolin-3 deficiency and hyperCKemia

Mutations in the caveolin-3 (CAV3) gene are associated with autosomal dominant limb-girdle muscular dystrophy (LGMD1C). The authors report a novel sporadic mutation in the CAV3 gene in two unrelated children with persistent elevated levels of serum creatine kinase (hyperCKemia) without muscle weakness. Immunohistochemistry and quantitative immunoblot analysis of caveolin-3 showed reduced expression of the protein in muscle fibers. Our data indicate that a partial caveolin-3 deficiency should be considered in the differential diagnosis of idiopathic hyperCKemia.     

Limb-girdle muscular dystrophy in a 71-year-old woman with an R27Q mutation in the CAV3 gene

The authors report a 71-year-old woman with limb-girdle muscular dystrophy (LGMD) associated with an R27Q mutation in the CAV3 gene. Immunohistochemistry showed a >90% reduction of caveolin-3 on the sarcolemma by western blot, and anti-dysferlin immunoreactivity was reduced. This case emphasizes that an R27Q missense mutation in the CAV3 gene can lead to various clinical phenotypes including hyperCKemia, rippling muscle disease, distal myopathy, and LGMD1C.     

Novel splice site mutation in the caveolin-3 gene leading to autosomal recessive limb girdle muscular dystrophy

Mutations in CAV3 gene encoding the protein caveolin-3 are associated with autosomal dominant limb girdle muscular dystrophy 1C, rippling muscle disease, hyperCKemia, distal myopathy, hypertrophic cardiomyopathy and rare autosomal recessive limb girdle muscular dystrophy phenotypes. In a 57-year-old patient with asymmetric limb girdle weakness, we detected a novel homozygous intronic mutation (IVS1 + 2T > C) of the CAV3 gene. This is the first splicing mutation reported for CAV3. These findings add to the clinical and genetic variability of CAV3 mutations.     

Variable cardiac involvement in Tunisian siblings harboring FKRP gene mutations

Mutations in the gene encoding fukutin-related protein (FKRP) cause limb-girdle muscular dystrophy 2I (LGMD2I) and congenital muscular dystrophy (MDC1C). Cardiac involvement was frequently reported with numerous mutations including C826A and 1364C > A mutations. The original Tunisian family with LGMD2I included 12 patients sharing the LGMD phenotype and homozygous to the 1486T > A mutation but who did not display any cardiac involvement. In this study, we report the clinical data, cardiac assessment and mutation analysis in four sibs belonging to a second Tunisian LGMD2I family. All patients showed the LGMD phenotype, the oldest brother and sister had mild cardiac involvement, whereas two twin sisters displayed severe cardiomyopathy leading to death. The patients shared the compound heterozygous 1486T > A, 1364C > A mutation in the FKRP gene suggesting that the association of a compound heterozygous state of mutation responsible for LGMD2I and the MDC1C phenotype could lead to cardiac involvement.     

A novel missense mutation in the caveolin-3 gene in rippling muscle disease

Rippling muscle disease (RMD) is a benign myopathy with symptoms and signs of muscular hyperirritability. We report a 17-year-old patient who presented with muscular hypertrophy, local mounding on percussion, and a rippling phenomenon. Needle electromyography showed electrical silence during the rippling phenomenon. Muscle protein immunohistochemical analysis showed a partial deficiency of caveolin-3. Molecular analysis revealed a novel heterozygous A>C transition at nucleotide position 140 in exon 2 of the caveolin-3 gene. We associated this novel mutation with RMD.     

High prevalence and phenotype-genotype correlations of limb girdle muscular dystrophy type 2I in Denmark

OBJECTIVES: The prevalence of limb girdle muscular dystrophy type 2I (LGMD2I) in northern Europe is unknown. We investigated this and the genotype-phenotype relation in LGMD2I. METHODS: Prospective clinical and molecular screening of 118 Danish patients registered with LGMD was performed to divide patients into LGMD subtypes. RESULTS: One hundred three patients fulfilled the clinical criteria for LGMD2. Thirty-eight had LGMD2I (27 homozygous, 11 compound heterozygous for 826C>A), 23 had sarcoglycanopathy, 2 dysferlinopathy, 12 calpainopathy, and 4 Becker muscular dystrophy. The 24 patients with no molecular diagnosis did not harbor fukutin-related protein gene (FKRP) mutations. A clear clinical delineation was found between patients homozygous and compound heterozygous for the 826C>A mutation. Homozygous patients had later debut, milder clinical progression, and less muscle weakness compared with compound heterozygous patients, who were all wheelchair bound by their mid-20s. Impaired cardiac pump function was found in both groups. INTERPRETATION: This study reports a different distribution of LGMD subtypes in Denmark than seen in other geographic regions, with a threefold to fourfold higher prevalence of LGMD2I than elsewhere. The findings support a clear clinical delineation between patients homozygous and compound heterozygous for the 826C>A mutation in FKRP. The findings suggest that, in the studied region, screening for the 826C>A mutation will identify all persons with LGMD2I.     

Enrichment of the R77C alpha-sarcoglycan gene mutation in Finnish LGMD2D patients

Limb-girdle muscular dystrophy 2D (LGMD2D) is caused by mutations in the alpha-sarcoglycan gene (SGCA). The most frequently reported mutation, 229CGC>TGC (R77C) in exon 3 of SGCA, results in the substitution of arginine by cysteine. We present here the clinical, immunohistochemical, and genetic data of 11 Finnish patients with LGMD2D caused by mutations in SGCA. Mutational analysis showed 10 patients homozygous and 1 compound heterozygous for R77C. A wide spectrum of SGCA mutations has been reported previously. Our results show an enrichment of R77C in Finland, further underlined by the observed carrier frequency of 1 per 150. According to the annual birth rate of approximately 60,000 in Finland, one LGMD2D patient with a homozygous mutation is expected to be born every 1 or 2 years on average. The presence of an ancient founder mutation is indicated by the fact that all patients shared a short common haplotype extending > or = 790 kilobases. Our results emphasize the need to include the SGCA gene R77C mutation test in routine DNA analyses of severe dystrophinopathy-like muscular dystrophies in Finland, and suggest that the applicability of this test in other populations should be studied as well.     

A novel in-frame deletion in the CAV3 gene in a Korean patient with rippling muscle disease

Rippling muscle disease (RMD) is a rare form of myopathy that is characterized by percussion-induced rapid muscle contractions, muscle mounding, and rippling. Recently a caveolin-3 gene (CAV3) mutation was identified in patients suffering from autosomal dominant RMD. We encountered a Korean male patient with RMD who had suffered from muscle stiffness for 3 years. Mutation analysis of the CAV3 gene revealed the patient to be heterozygous for a novel in-frame deletion mutation (c.307_312delGTGGTG; Phe103_Phe104del). Further analysis of his family members showed that his mother and elder sister also have the same mutation. To the best of our knowledge, this is the first report of genetically confirmed RMD in Korea.     

Variable reduction of caveolin-3 in patients with LGMD2B/MM

Abstract. Mutations in the human dysferlin gene (DYSF) cause autosomal recessive muscular dystrophies characterized by degeneration and weakness of proximal and/or distal muscles: limb girdle muscular dystrophy type 2B (LGMD2B) and Miyoshi myopathy (MM). Recently, an interaction between caveolin-3 and dysferlin in normal and dystrophic muscle (primary caveolin-3 deficiency; LGMD1C) was shown. In this study, clinical,morphological and genetic analysis was carried out in four independent LGMD2B/MM patients. All patients presented with an adult-onset, slowly progressive muscular dystrophy with variable involvement of proximal and distal muscles. We found complete lack of dysferlin in the four LGMD2B/MM patients. Secondary reduction of caveolin-3 was detected in three out of the four patients. Regular caveolae were detected along the basal lamina in two patients by electron microscopy. We provide further evidence that dysferlin and caveolin-3 interact in human skeletal muscle. It remains to be elucidated whether the loss of this interaction contributes to pathogenic events in muscular dystrophy.M. C. Walter and C. Braun contributed equally.     

Frequency and characterisation of anoctamin 5 mutations in a cohort of Italian limb-girdle muscular dystrophy patients

Limb-girdle muscular dystrophy (LGMD) 2L, caused by mutations in the anoctamin 5 (ANO5) gene, is the third most common LGMD in Northern and Central Europe, where the c.191dupA mutation causes the majority of cases. We evaluated data from 228 Italian LGMD patients to determine the prevalence of LGMD2L and the c.191dupA mutation, and to describe the clinical, muscle biopsy, and magnetic resonance imaging findings in these patients. Forty-three patients who lacked molecular diagnosis were studied for ANO5 mutations, and four novel mutations were found in three probands. Only one proband carried the c.191dupA mutation, which was compound heterozygous with c.2516T>G. Two probands were homozygous for the c.1627dupA and c.397A>T mutations, respectively, while a fourth proband had a compound heterozygous status (c.220C>T and c.1609T>C). Therefore occurrence and molecular epidemiology of LGMD2L in this Italian cohort differed from those observed in other European countries. ANO5 mutations accounted for ∼2% of our sample. Affected patients exhibited benign progression with variable onset and an absence of cardiac and respiratory impairment; muscle biopsy generally showed mild signs, except when performed on the quadriceps muscles; MRI showed predominant involvement of the posterior thigh. Overall these common clinical, morphological and imaging findings could be useful in differential diagnosis.     

Muskeldystrophie infolge Anoctamin-5-Mutationen

Recessive mutations in the anoctamin 5 (ANO5) gene have been recently identified in families with limb girdle muscular dystrophy (LGMD2L) and distal non-dysferlin Miyoshi myopathy. Anoctamin 5 is supposed to be a putative calcium-activated chloride channel. We report five German patients (four index patients) with muscle dystrophy due to mutations in the ANO5 gene. Sequencing of the ANO5 exons 5, 13 and 20 was performed to screen for a common c.191dupA mutation and two other reported mutations (c.1295C>G and p.R758C). The whole coding region of the ANO5 gene was sequenced to identify new mutations. Phenotypically, three patients showed LGMD and one patient Miyoshi type distal myopathy. One sibling had asymptomatic hyperCKemia. The age at onset was 64, 38 and 40 years in patients with LGMD and 23 years in the patient with distal myopathy. The four symptomatic patients showed remarkable asymmetric muscle involvement. There was marked CK elevation (11 to 30 times). Electron microscopy showed multifocal gaps in the sarcolemmal membrane. All patients harboured the common c.191dupA mutation in at least one allele. Two patients with LGMD were homozygous and the third patient and his asymptomatic sister were compound heterozygous for the c.191dupA mutation and a novel p.T548I mutation. The patient with distal myopathy harboured the p.R758C mutation in the second allele. Mutations in the ANO5 gene seem to be a relatively common cause of muscular dystrophy in Germany. Cases with late onset or asymptomatic hyperCKemia can occur. Clinically, asymmetric manifestation is typical.     

Thought ripples on muscle waves: recognition of rippling muscle disease

We report on a 16-year-old Dutch patient in whom rippling muscle disease (RMD) was diagnosed years after his mother had been falsely diagnosed with acid maltase deficiency. The autosomal dominant mode of inheritance of the neuromuscular symptoms in this family had led to a re-evaluation of the diagnosis of acid maltase deficiency. Physical examination revealed the three key features leading to the clinical diagnosis of RMD: rippling, mounding, and percussion-induced rapid muscle contraction. Mutation analysis revealed a novel heterozygous missense mutation in the caveolin-3 gene (c.79C > G; p.Arg27Gly) in both the index patient and his mother. This case report stresses the importance of adhering to the mode of inheritance in the diagnosis of neuromuscular disorders. It also indicates that typical RMD phenomena are not easily acknowledged among paediatricians or neurologists. We therefore present an overview of these clinical characteristics of rippling muscle disease RMD.     

Rippling muscle disease and facioscapulohumeral dystrophy-like phenotype in a patient carrying a heterozygous CAV3 T78M mutation and a D4Z4 partial deletion: Further evidence for "double trouble" overlapping syndromes

We report the first case of a heterozygous T78M mutation in the caveolin-3 gene (CAV3) associated with rippling muscle disease and proximal myopathy. The patient displayed also bilateral winged scapula with limited abduction of upper arms and marked asymmetric atrophy of leg muscles shown by magnetic resonance imaging. Immunohistochemistry on the patient's muscle biopsy demonstrated a reduction of caveolin-3 staining, compatible with the diagnosis of caveolinopathy. Interestingly, consistent with the possible diagnosis of FSHD, the patient carried a 35 kb D4Z4 allele on chromosome 4q35. We discuss the hypothesis that the two genetic mutations may exert a synergistic effect in determining the phenotype observed in this patient.     

Cardiac assessment of limb-girdle muscular dystrophy 2I patients: an echography, Holter ECG and magnetic resonance imaging study

Mutations in the FKRP gene may be associated with cardiac involvement. The aim of our study was to assess myocardial involvement in patients with LGMD2I, using physical examination, echocardiography, resting and 24-h ambulatory electrocardiogram and cardiac magnetic resonance imaging, with particular attention to the detection of myocardial morphologic abnormalities. Patients were compared to matched controls. Twenty-three patients were enrolled (men 10 - women 13; 32.3+/-9.5 years). Twenty-two had the C826A gene mutation (homozygous 12, heterozygous 10). Nine patients had severe muscle alterations, 10 had milder muscle involvement and 4 had isolated exertional myoglobinuria. When compared to controls, LGMD2I patients had reduced left ventricular ejection fraction (50.8+/-13.9 versus 66.6+/-3.8%, p<0.0001). Sixty percent of patients had reduced left ventricular ejection fraction, including 8% with severe reduced left ventricular ejection fraction <30%. None had significant arrhythmia. Gene mutation and the severity of the muscle disease were not predictive of cardiac involvement. Cardiac magnetic resonance imaging displayed a high prevalence of myocardial functional abnormalities, fatty replacement and fibrosis, among the 13 patients investigated. Reduced contractility and cardiac magnetic resonance imaging morphological abnormalities are highly prevalent in LGMD2I patients suggesting that all patients should be referred for cardiac evaluation.