Ullrich Congenital Muscular Dystrophy 1
A number sign (#) is used with this entry because of evidence that Ullrich congenital muscular dystrophy-1 (UCMD1) can be caused by mutation in any of 3 genes encoding the subunits of collagen type VI (COL6A1, 120220; COL6A2, 120240; and COL6A3, 120250). Both recessive (homozygous) and dominant (heterozygous) mutations have been reported.
See also Bethlem myopathy-1 (BTHLM1; 158810), an allelic disorder that shows autosomal dominant inheritance and a milder phenotype.
DescriptionUllrich congenital muscular dystrophy is characterized by generalized muscle weakness and striking hypermobility of distal joints in conjunction with variable contractures of more proximal joints and normal intelligence. Additional findings may include kyphoscoliosis, protruded calcanei, and follicular hyperkeratosis. Some patients manifest at birth and never achieve independent ambulation, whereas others maintain ambulation into adulthood. Progressive scoliosis and deterioration of respiratory function is a typical feature (summary by Kirschner, 2013).
Genetic Heterogeneity of Ullrich Congenital Muscular Dystrophy
UCMD2 (616470) is caused by mutation in the COL12A1 gene (120320) on chromosome 6q.
NomenclatureAt the 229th ENMC international workshop, Straub et al. (2018) classified Ullrich congenital muscular dystophy caused by mutation in one of the collagen VI genes, which they called recessive Bethlem myopathy, as a form of limb-girdle muscular dystrophy (LGMDR22).
Clinical FeaturesUllrich (1930) described a congenital muscular dystrophy that he called 'scleroatonic muscular dystrophy.' In most cases, muscle weakness and multiple contractures were noted at birth or in early infancy. Furukawa and Toyokura (1977) described affected sibs. The limitation of motion in axial and proximal joints suggested a rigid spine syndrome. The patients often have hyperextensibility in distal joints, suggesting the Ehlers-Danlos syndrome (see 130000).
Ricci et al. (1988) described brother and sister with relatively late onset of manifestations. The sister was found to have bilateral hip dislocation at 16 months and difficulty climbing stairs at 3 years. The patient died at age 13 years of recurrent bronchopneumonia. The brother was noted to have a clumsy gait and difficulty climbing stairs at the age of 3 years. Contractures at the elbows were evident at age 12 and the spine appeared rigid. De Paillette et al. (1989) found reports of other affected sibs as well as several instances of first-cousin parents. Proximal contractures, distal hyperextensibility, and hyperhidrosis were commented on. Wiedemann (1991) stated that about 20 cases were known.
Mercuri et al. (2002) described 15 patients with Ullrich congenital muscular dystrophy. All of the patients presented within the first months of life with hypotonia, contractures, torticollis, or hip dislocation. Eight of the patients acquired ambulation or had only mild motor delay, whereas 7 had severe motor disability. Most patients had characteristic round facies and long, thin extremities with wasting of the muscles. All had generalized weakness, rigidity of the spine, and respiratory insufficiency with tendency toward recurrent chest infections.
Lampe and Bushby (2005) provided a review of collagen VI-related muscle disorders.
Nadeau et al. (2009) reported the natural history of 13 patients with UCMD. The mean age at symptom onset was 12 months, with delayed motor development and proximal weakness, but 6 patients had a congenital presentation with variable combinations of congenital hip dislocation (2), hypotonia (3), contractures (4), torticollis (2), scoliosis (1), and feeding difficulties (2). Eight patients (61.5%) acquired independent ambulation, none ever ran, and 9 were wheelchair-dependent at a mean age of 11 years. All patients developed multiple joint contractures in the first decade of life, including of the long finger flexors. Twelve patients had scoliosis, 6 had kyphosis, and many had rigid spine. All patients developed progressive respiratory insufficiency from age 6 years on, and most required nocturnal ventilation; 2 died of respiratory failure at ages 10.8 and 15.1 years. Eight patients were underweight and 7 described chewing difficulties; 3 required gastrostomy. Eight patients had follicular hyperkeratosis and 3 had abnormal scarring with keloid formation. Serum creatine kinase was mildly increased, and staining for collagen VI was abnormal in all patients examined. All patients had normal cognitive abilities and cardiac function. Overall, most patients had rapid deterioration of respiratory function in the first decade of life, but this deterioration was not correlated with age or severity at presentation.
PathogenesisIn a boy with Ullrich disease, Ishikawa et al. (2002) identified compound heterozygosity in the COL6A2 gene (120240) and complete deficiency of collagen VI by immunohistochemistry in the patient's muscle biopsy. Expression of collagen IV (see 120130), a major component of the basal lamina, was normal. Electron microscopy showed a total absence of microfibrils, which are usually seen in the interstitium associated with collagen fibrils. Ishikawa et al. (2002) suggested that loss of anchoring between the basal lamina and the interstitium may be the molecular mechanism of muscular dystrophy.
Angelin et al. (2007) identified significantly increased apoptosis in skeletal muscle biopsies and myoblast cultures from 5 unrelated patients with variable severity of Ullrich congenital muscular dystrophy. Addition of oligomycin, a selective mitochondrial inhibitor, resulted in mitochondrial depolarization of myoblasts from UCMD patients but not from healthy controls. Electron microscopy showed abnormal mitochondrial morphology, including less elongation, increased size, and hypodense matrix with absence of cristae. Plating on collagen VI or treatment with cyclosporin A or calcium chelators normalized all of these findings and decreased apoptosis. The response to cyclosporin A suggested an inappropriate opening defect in the permeability transition pore, since the drug desensitizes the pore. Angelin et al. (2007) concluded that mitochondrial dysfunction is involved in the pathogenesis of Ullrich congenital muscular dystrophy.
Kawahara et al. (2007) observed sarcolemmal-specific collagen VI deficiency in muscle biopsies from patients with a heterozygous COL6A1 G284R mutation (120220.0012) in the N-terminal region in the triple helical domain. Collagen VI was present in the interstitium but was barely detectable in the sarcolemma; patients with compound heterozygous COL6A1 mutations had complete absence of the protein. Electron microscopy showed that collagen VI microfibrils did not bind to the basement membrane. Further studies showed that fibroblasts with the mutation assembled and secreted normal collagen VI microfibrils. However, cell adhesion of heterozygous G284R fibroblasts was markedly decreased, similar to that of collagen VI-deficient cells, but could be rescued by the addition of normal collagen VI. Kawahara et al. (2007) concluded that heterozygous mutations in the COL6A1 gene result in decreased binding of collagen VI to the extracellular matrix.
Voermans et al. (2007) reported a patient with Ehlers-Danlos syndrome (EDS; 606408) who had a homozygous mutation in the TNXB gene (600985.0002). In addition to classic clinical features of EDS, such as mild joint hypermobility, skin hyperextensibility, and easy bruising since childhood, she also had progressive generalized muscle weakness and distal contractures beginning at about age 40. She was unable to walk up stairs, had limited walking endurance of 1 hour, and had reduced gripping force. Needle biopsy of the quadriceps muscle did not show significant myopathic changes, but there was absence of immunostaining to tenascin XB and decreased endomysial staining for collagen VI. Voermans et al. (2007) noted that disruption of the TNXB gene, which is part of the extracellular matrix in skeletal muscle, results in decreased expression of type VI collagen. Thus, some patients with EDS due to tenascin deficiency may show myopathic features of collagen VI-related myopathies, such as Ullrich congenital muscular dystrophy. Kirschner et al. (2005) had previously suggested an overlap in ultrastructural connective tissue abnormalities between patients with UCMD and EDS, namely, changes in collagen fibril morphology and increased ground substance. All 5 UCMD patients examined by Kirschner et al. (2005) had distal joint hypermobility, and some patients had abnormal scar formation, poor wound healing, and velvety skin texture as observed in EDS.
Pace et al. (2008) reported 8 patients with UCMD caused by heterozygous glycine mutations toward the N-terminal of the triple helix of the collagen VI molecule. Studies of patient fibroblasts showed that all the mutations compromised intracellular assembly and disulfide bonding of the collagen VI tetramers. The mutations produced 2 assembly phenotypes that reflected severity. In the mild group, collagen VI dimers accumulated in the cell but not the medium, microfibril formation in the medium was moderately reduced, and the amount of collagen VI in the extracellular matrix was not significantly altered. The more severe group had more severe collagen assembly defects: some secreted collagen VI tetramers were not disulfide bonded, microfibril formation in the medium was severely compromised, and collagen VI in the extracellular matrix was reduced. These data indicate that collagen VI glycine mutations can impair the assembly pathway in different ways that correlate with disease severity. In mildly affected patients, normal amounts of collagen VI were deposited in the fibroblast matrix, whereas in patients with moderate to severe disability, assembly defects led to a reduced collagen VI fibroblast matrix.
Clinical ManagementMerlini et al. (2008) found that treatment of 4 UCMD patients with 2 divided doses of orally administered cyclosporin A resulted in decreased mitochondrial dysfunction and apoptosis in skeletal muscle biopsies 1 month later. Cellular signs of muscle regeneration were also observed. Clinical response could not be assessed because of the limited time frame, but the study provided a proof of principle and suggested that mitochondrial dysfunction may play a role in the pathogenesis of the disorder.
Cyclosporine A acts as an inhibitor of opening of the mitochondrial permeability transition pore (PTP). Opening of the PTP allows equilibration of the ionic charge between the mitochondrial matrix and the intermembrane space, causing depolarization of the electrochemical gradient used to generate ATP and prompting apoptosis. Hicks et al. (2009) found evidence for PTP dysregulation in muscle cell lines, but not fibroblasts, from 2 UCMD patients. PTP dysregulation was also observed in LGMD2B (253601) myoblasts, but not in myoblasts from patients with several other muscular dystrophies. Further studies led Hicks et al. (2009) to conclude that PTP dysregulation may be a characteristic of cells in culture and not specific to a collagen VI defect, calling into question the results of Merlini et al. (2008). In a reply, Bernardi et al. (2009) noted that the findings of Hicks et al. (2009) actually supported their original results (Merlini et al., 2008), since they had studied myoblasts, not fibroblasts. Bernardi et al. (2009) cited the studies of Angelin et al. (2007), who found that cyclosporin A normalized mitochondrial dysfunction in myoblasts, and of Irwin et al. (2003), who demonstrated that treatment of Col6a1 -/- mice with cyclosporin A rescued the muscle ultrastructural defects and markedly decreased the number of apoptotic nuclei in vivo.
HeterogeneityGenetic Heterogeneity
Mercuri et al. (2002) sought abnormalities in collagen VI in 15 affected patients. Muscle biopsy examination for collagen VI in 11 patients showed 5 with a marked reduction, 1 with a mild reduction, and 5 with normal expression of collagen VI. Genetic linkage analysis of 6 families linked 3 with collagen VI loci (COL6A1, 120220; COL6A2, 120240; and COL6A3, 120250) and excluded 3 families. In sum, 6 of 15 patients had evidence of primary collagen VI involvement. The clinical features were similar in both groups, and did not segregate with collagen VI status. Mercuri et al. (2002) concluded that although collagen VI involvement is common in this disease, the role of this molecule was excluded in a number of cases, suggesting genetic heterogeneity of UCMD.
Lampe et al. (2005) sequenced all 3 COL6 genes from genomic DNA in 79 patients with UCMD or Bethlem myopathy, and found putative mutations in 1 of the COL6 genes in 62% of patients. Some patients showed changes in more than one of the COL6 genes, and some UCMD patients appeared to have dominant rather than recessive disease. Lampe et al. (2005) concluded that these findings may explain some or all of the cases of UCMD that are unlinked to the COL6 gene under a recessive model and noted that the large number of SNPs generated in this study may be of importance in determining the major phenotypic variability seen in this group of disorders.
Molecular GeneticsCamacho Vanegas et al. (2001) demonstrated recessive mutations in COL6A2 as the cause of UCMD (see, e.g., 120240.0002-120240.0004).
Demir et al. (2002) stated that UCMD behaving as an autosomal recessive disorder and characterized by generalized muscle weakness, contractures of multiple joints, and distal hyperextensibility could also be caused by homozygous mutations in the COL6A3 gene (see, e.g., 120250.0002 and 120250.0003).
Pan et al. (2003) identified a de novo heterozygous deletion near a minisatellite DNA sequence in intron 8 of the COL6A1 gene that removed 1.1 kb of genomic DNA encompassing exons 9 and 10 (120220.0006), resulting in a severe form of classic UCMD.
In 3 unrelated patients with UCMD, all born of consanguineous parents, Giusti et al. (2005) identified homozygous mutations in the COL6A1 gene (120220.0009-120220.0011).
Among 13 patients from 11 families with UCMD, Nadeau et al. (2009) found that 4 patients, including 2 sibs, were heterozygous for a COL6A1 mutation (see, e.g., 120220.0012); 2 were heterozygous for a COL6A2 mutation (see, e.g., 120240.0013), 4, including 2 cousins, were homozygous for a COL6A2 mutation (see, e..g, 120240.0012), and 2 were heterozygous for a COL6A3 mutation (120250.0004). One patient was compound heterozygous for mutations in COL6A1 (G281R; 120220.0014) and COL6A2 (R498H; 120240.0014), consistent with digenic inheritance. No genotype/phenotype correlations were noted.
Foley et al. (2011) reported large genomic deletions of chromosome 21q22.3 involving the COL6A1 and/or COL6A2 genes in 2 unrelated individuals with UCMD. One patient was compound heterozygous for a splice site mutation in COL6A2 and a 69-kb deletion involving COL6A2, whereas the other was compound heterozygous for a 47-kb deletion involving COL6A2 and a 1.61-Mb deletion involving COL6A1, COL6A2, and several surrounding genes. The 4 asymptomatic parents were each heterozygous for 1 of the molecular defects. Skin biopsies from the second patient and his asymptomatic mother who was heterozygous for the 1.61-Mb deletion showed absent and decreased collagen VI staining, respectively. A third patient with global developmental delay and axial hypotonia, but not frank UCMD, was heterozygous for a 1.09-Mb deletion involving the COL6A1 and COL6A2 genes inherited from his asymptomatic father. Foley et al. (2011) emphasized that the heterozygous carrier parents were asymptomatic, indicating that haploinsufficiency of these genes is not a disease mechanism for Bethlem myopathy, despite the finding of decreased collagen VI deposition.
Genotype/Phenotype CorrelationsBaker et al. (2005) studied 5 patients with a clinical diagnosis of UCMD. Three patients had heterozygous in-frame deletions in the N-terminal region of the triple helical domain of type VI collagen (see, e.g., COL6A2 120240.0008 and COL6A3 120250.0004). Protein biosynthesis and assembly studies showed that these mutations acted in a dominant-negative fashion and resulted in severe collagen VI matrix deficiencies. One patient had recessive amino acid changes in the C2 subdomain of COL6A2, which prevented collagen VI assembly. No collagen VI mutations were found in a fifth patient. Baker et al. (2005) concluded that dominant mutations may be common in UCMD and that mutation detection remains critical for accurate genetic counseling.
In 2 patients with UCMD, Giusti et al. (2005) identified heterozygous missense mutations in the COL6A1 gene (120220.0012 and 120220.0013). The mutations occurred at glycine residues in exons 9 and 10, respectively, the same exons deleted in the patient reported by Pan et al. (2003). Both patients had a milder phenotype than that seen in classic cases, as well as reduced but not absent collagen VI protein in muscle cells and fibroblasts. The findings confirmed that dominant mutations in the COL6A1 gene can result in UCMD.
Brinas et al. (2010) classified 49 patients with muscular dystrophy due to mutations in 1 of the 3 COL6A genes into 3 clinical groups: 9 (18%) had a severe phenotype with contractures and never achieved ambulation, 26 (53%) had a moderate phenotype and were initially able to walk but tended to lose ambulation later in childhood, and 14 (29%) had a milder course and remained ambulatory at a mean age of 20 years. All patient fibroblasts showed absent or reduced COL6A secretion, with frequent intracellular retention, and the decreased levels correlated with increased disease severity. Genetic analysis showed equal distribution of mutations across the cohort: 17 (30%) in COL6A1, 26 (46%) in COL6A2, and 13 (23%) in COL6A3. Thirty patients (61%) had dominant de novo mutations, and 18 had recessive mutations. Fourteen patients (28.5%) had truncating mutations. Homozygous truncating mutations before or within the triple helix (TH) domain were associated with the most severe phenotypes. The moderate phenotype was associated with heterozygous mutations resulting in the skipping of part of the TH domains or affecting the glycine residue of the Gly-X-Y domain. RT-PCR analysis was helpful in defining the effect of splice site mutations.
Substitutions in the conserved Gly-X-Y motif in the triple helix (TH) domain of collagen VI are the most commonly identified mutations in the collagen VI myopathies, accounting for almost one-third of all pathogenic mutations. Butterfield et al. (2013) analyzed genotype/phenotype correlations of 194 individuals with Gly substitutions in the TH domain of the COL6A1, COL6A2, or COL6A3 genes. The cohort included 97 newly reported cases and 97 published cases. In all 3 genes, 89% of the mutations clustered in the N-terminal regions before the 17th Gly-X-Y triplet (TH17). This important landmark is delineated by cysteine residues in the COL6A3 chain, which form disulfide bonds stabilizing tetramers. Patients with mutations inside the critical region of Gly-X-Y triplets 10-15 tended to have a more severe phenotype than those with mutations outside this critical region. However, identical glycine substitutions were associated with both severe and mild phenotypes. The most commonly observed mutation was G284R in the COL6A1 gene (120220.0012), found in 28 cases with variable phenotypes. Glycine substitutions in the TH domain were dominantly acting in 96% of cases, and recessive mutations tended to occur in the C-terminal end of the TH domain. Butterfield et al. (2013) concluded that the clustering of glycine substitutions in this region is not based on features of the primary sequence, but rather reflects a functional importance of this domain.
Population GeneticsOkada et al. (2007) determined that primary collagen VI deficiency is the second most common congenital muscular dystrophy in Japan after Fukuyama congenital muscular dystrophy (FCMD), now designated muscular dystrophy-dystroglycanopathy type A4 (MDDGA4; 253800). Collagen VI deficiency accounted for 26 (7.2%) of 362 Japanese patients with a clinical diagnosis of congenital muscular dystrophy. There were no genotype/phenotype correlations.
HistoryWiedemann (1991) gave an account of Otto Ullrich (1894-1957) that included information on his teacher, von Pfaundler, his career, his personality, and 'his' syndromes.