Diagnosis and etiology of congenital muscular dystrophy

Objective: We aimed to determine the frequency of all known forms of congenital muscular dystrophy (CMD) in a large Australasian cohort. Methods: We screened 101 patients with CMD with a combination of immunofluorescence, Western blotting, and DNA sequencing to identify disease-associated abnormalities in glycosylated α-dystroglycan, collagen VI, laminin α2, α7-integrin, and selenoprotein. Results: A total of 45% of the CMD cohort were assigned to an immunofluorescent subgroup based on their abnormal staining pattern. Abnormal staining for glycosylated α-dystroglycan was present in 25% of patients, and approximately half of these had reduced glycosylated α-dystroglycan by Western blot. Sequencing of the FKRP , fukutin , POMGnT1 , and POMT1 genes in all patients with abnormal α-dystroglycan immunofluorescence identified mutations in one patient for each of these genes and two patients had mutations in POMT2 . Twelve percent of patients had abnormalities in collagen VI immunofluorescence, and we identified disease-causing COL6 mutations in eight of nine patients in whom the genes were sequenced. Laminin α2 deficiency accounted for only 8% of CMD. α7-Integrin staining was absent in 12 of 45 patients studied, and ITGA7 gene mutations were excluded in all of these patients. Conclusions: We define the distribution of different forms of congenital muscular dystrophy in a large cohort of mixed ethnicity and demonstrate the utility and limitations of current diagnostic techniques.