Mutations in C0L6A], COL6A2 and COL6A3, the genes which encode the extracellular matrix component collagen VI, lead to Bethlem myopathy BM Ullrich Congenital Muscular Dystrophy (UCMD) and myosclerosis myopathy. Unlike UCMD, BM is difficult to diagnose due to its clinical overlap with other contractural phenotypes and the lack of sensitivity of standard immunohistochemica! diagnostic techniques in muscle biopsy samples. This thesis investigates the potential of two prospective diagnostic techniques, and proposes an algorithm for better BM diagnosis based on immunofluorescent labelling of collagen VI in skin biopsy-derived fibroblast cells.