Meganne Leach

Large genomic deletions: A novel cause of Ullrich congenital muscular dystrophy

Two mutational mechanisms are known to underlie Ullrich congenital muscular dystrophy (UCMD): heterozygous dominant negatively‐acting mutations and recessively‐acting loss‐of‐function mutations. We describe large genomic deletions on chromosome 21q22.3 as a novel type of mutation underlying recessively inherited UCMD in 2 families. Clinically unaffected parents carrying large genomic deletions of COL6A1and COL6A2also provide conclusive evidence that haploinsufficiency for COL6A1and COL6A2is not a disease mechanism for Bethlem myopathy. Our findings have important implications for the genetic evaluation of patients with collagen VI–related myopathies as well as for potential therapeutic interventions for this patient population. Ann Neurol 2011;69:206–211

Mosaicism for dominant collagen 6 mutations as a cause for intrafamilial phenotypic variability.

Collagen 6‐related dystrophies and myopathies (COL6‐RD) are a group of disorders that form a wide phenotypic spectrum, ranging from severe Ullrich congenital muscular dystrophy, intermediate phenotypes, to the milder Bethlem myopathy. Both inter‐ and intrafamilial variable expressivity are commonly observed. We present clinical, immunohistochemical, and genetic data on four COL6‐RD families with marked intergenerational phenotypic heterogeneity. This variable expression seemingly masquerades as anticipation is due to parental mosaicism for a dominant mutation, with subsequent full inheritance and penetrance of the mutation in the heterozygous offspring. We also present an additional fifth simplex patient identified as a mosaic carrier. Parental mosaicism was confirmed in the four families through quantitative analysis of the ratio of mutant versus wild‐type allele (COL6A1, COL6A2, and COL6A3) in genomic DNA from various tissues, including blood, dermal fibroblasts, and saliva. Consistent with somatic mosaicism, parental samples had lower ratios of mutant versus wild‐type allele compared with the fully heterozygote offspring. However, there was notable variability of the mutant allele levels between tissues tested, ranging from 16% (saliva) to 43% (fibroblasts) in one mosaic father. This is the first report demonstrating mosaicism as a cause of intrafamilial/intergenerational variability of COL6‐RD, and suggests that sporadic and parental mosaicism may be more common than previously suspected.

Results of a two-year pilot study of clinical outcome measures in collagen VI- and laminin alpha2-related congenital muscular dystrophies

Potential therapies are currently under development for two congenital muscular dystrophy (CMD) subtypes: collagen VI-related muscular dystrophy (COL6-RD) and laminin alpha 2-related dystrophy (LAMA2-RD). However, appropriate clinical outcome measures to be used in clinical trials have not been validated in CMDs. We conducted a two-year pilot study to evaluate feasibility, reliability, and validity of various outcome measures, particularly the Motor Function Measure 32, in 33 subjects with COL6-RD and LAMA2-RD. In the first year, outcome measures tested included: Motor Function Measure 32 (MFM32), forced vital capacity (FVC) percent predicted sitting, myometry, goniometry, 10-meter walk, Egen Klassification 2, and PedsQL(TM) Generic and Neuromuscular Cores. In the second year, we added the North Star Ambulatory Assessment (NSAA), Hammersmith Functional Motor Scale (HFMS), timed functional tests, Measure of Activity Limitations (ACTIVLIM), Quality of Upper Extremity Skills Test (QUEST), and Patient-Reported Outcomes Measurement Information System (PROMIS) fatigue subscale. The MFM32 showed strong inter-rater (0.92) and internal consistency (0.96) reliabilities. Concurrent validity for the MFM32 was supported by large correlations (range 0.623-0.936) with the following: FVC, NSAA, HFMS, timed functional tests, ACTIVLIM, and QUEST. Significant correlations of the MFM32 were also found with select myometry measurements, mainly of the proximal extremities and domains of the PedsQL(TM) scales focusing on physical health and neuromuscular disease. Goniometry measurements were less reliable. The Motor Function Measure is reliable and valid in the two specific subtypes of CMD evaluated, COL6-RD and LAMA2-RD. The NSAA is useful as a complementary outcome measure in ambulatory individuals. Preliminary concurrent validity of several other clinical outcome measures was also demonstrated for these subtypes.

Comparison of sitting and supine forced vital capacity in collagen VI-related dystrophy and laminin α2-related dystrophy: Sitting and Supine FVC in COL6-RD and LAMA2-RD

Progressive, restrictive, respiratory insufficiency is the major cause of morbidity and mortality in Congenital Muscular Dystrophy (CMD). Nocturnal hypoventilation precedes daytime alveolar hypoventilation, and if untreated, may lead to respiratory failure and cor pulmonale. CMD consensus care guidelines recommend screening for respiratory insufficiency by conventional and dynamic (sitting to supine) pulmonary function testing (PFT) and evaluating for sleep disordered breathing if there is more than 20% relative reduction from sitting to supine FVC(L) (ΔFVC).

Upper extremity outcome measures for collagen VI-related myopathy and LAMA2-related muscular dystrophy

Congenital muscular dystrophy (CMD) comprises a rare group of genetic muscle diseases that present at birth or early during infancy. Two common subtypes of CMD are collagen VI-related muscular dystrophy (COL6-RD) and laminin alpha 2-related dystrophy (LAMA2-RD). Traditional outcome measures in CMD include gross motor and mobility assessments, yet significant motor declines underscore the need for valid upper extremity motor assessments as a clinical endpoint. This study validated a battery of upper extremity measures in these two CMD subtypes for future clinical trials. For this cross-sectional study, 42 participants were assessed over the same 2-5 day period at the National Institutes of Health Clinical Center. All upper extremity measures were correlated with the Motor Function Measure 32 (MFM32). The battery of upper extremity assessments included the Jebsen Taylor Hand Function Test, Quality of Upper Extremity Skills Test (QUEST), hand held dynamometry, goniometry, and MyoSet Tools. Spearman Rho was used for correlations to the MFM32. Pearson was performed to correlate the Jebsen, QUEST, hand-held dynamometry, goniometry and the MyoSet Tools. Correlations were considered significant at the 0.01 level (2-tailed). Significant correlations were found between both the MFM32 and MFM Dimension 3 only (Distal Motor function) and the Jebsen, QUEST, MyoGrip and MyoPinch, elbow flexion/extension ROM and myometry. Additional correlations between the assessments are reported. The Jebsen, the Grasp and Dissociated Movements domains of the QUEST, the MyoGrip and the MyoPinch tools, as well as elbow ROM and myometry were determined to be valid and feasible in this population, provided variation in test items, and assessed a range of difficulty in CMD. To move forward, it will be of utmost importance to determine whether these upper extremity measures are reproducible and sensitive to change over time.

T.P.42

Comparisons of clinical outcome measures of motor performance to be used in clinical trials in Congenital Muscular Dystrophy subtypes are limited. However, redundancy, discriminant validity, and ceiling and floor effects of motor function measures are an important consideration in optimizing the use of outcome measures clinical trials. Methods: We conducted a study to compare the Motor Function Measure 32 (MFM32), the Hammersmith Functional Motor Scale (HFMS), and the North Star Ambulatory Assessment (NSAA) in 29 subjects with COL6-RM and LAMA2-RD. We analyzed concurrent validity using Spearman rank order correlation, discriminant analysis using Wilcoxon Mann Whitney test, and floor and ceiling effects using a cut off of 20% for each item. We hypothesized that the HFMS and NSAA would expand the motor function assessment of the MFM32 in both extremes of functional limitations and disease severity (NSAA for higher functioning/less severe and HFMS for lower functioning/more severe). Concurrent validity for the MFM32, HFMS, and NSAA was strong as evidenced by large correlations (ranging 0.76–0.93, p p

G.P.214

Collagen VI-related dystrophies and myopathies (COL6-RD) are a highly variable group of disorders that form a phenotypic spectrum ranging from severe Ullrich congenital muscular dystrophy (UCMD) via intermediate phenotypes to the milder Bethlem myopathy (BM). Both inter- and intra-familial variable expressivity of severity are commonly observed. We present clinical, immunohistochemical, and genetic data on four families with marked inter-generational phenotypic variability masquerading as anticipation due to parental mosaicism for a dominant mutation, with subsequent full inheritance and penetrance of the mutation in the heterozygous offspring. Additionally, we present a 5th simplex patient identified as a mosaic carrier. Parental mosaicism was confirmed in the four families through quantitative analysis of the ratio of mutant versus wild type allele in genomic DNA from various tissues; including blood, saliva, and dermal fibroblasts. Consistent with somatic mosaicism parental samples had lower ratios of mutant versus wild type allele compared to the fully heterozygote offspring, although there was notable variability of the mutant between tissues tested, ranging from 16% (saliva) to 43% (fibroblasts) in one mosaic father. This is the first report demonstrating mosaicism as a cause of intra-familial/inter-generational variability of COL6-RD, suggesting that sporadic and parental mosaicism may be more common than previously suspected.

P1.11 Large genomic deletions as a novel type of mutation in Ullrich CMD

have performed oral function and swallowing test (ST) with surface electrode EMG and videofluoroscopic examination of swallowing (VF) in two unrelated very mild FCMD patients, who were able to walk and step up-down stairs in their childhood. Genomic DNA analysis of these cases showed 3 kb-RT insertion and no mutation in coding region and exon–intron junction of this gene. However, the haplotype analysis of the FKTN gene with six microsatellite markers revealed these patients have different haplotype from other severe type of FCMD. The ST showed severe dysfunction of swallowing in contradiction to their facial appearance and behavioral state. These results indicate that there may be potential risk for dysphagia and the periodical examination of ST is important for keeping the quality of life even in the very mild case of FCMD.