MedGen

Collagen VI-related dystrophies (COL6-RDs) represent a continuum of overlapping clinical phenotypes with Bethlem muscular dystrophy at the milder end, Ullrich congenital muscular dystrophy (UCMD) at the more severe end, and a phenotype in between UCMD and Bethlem muscular dystrophy, referred to as intermediate COL6-RD. Bethlem muscular dystrophy is characterized by a combination of proximal muscle weakness and joint contractures. Hypotonia and delayed motor milestones occur in early childhood; mild hypotonia and weakness may be present congenitally. By adulthood, there is evidence of proximal weakness and contractures of the elbows, Achilles tendons, and long finger flexors. The progression of weakness is slow, and more than two thirds of affected individuals older than age 50 years remain independently ambulatory indoors, while relying on supportive means for mobility outdoors. Respiratory involvement is not a consistent feature. UCMD is characterized by congenital weakness, hypotonia, proximal joint contractures, and striking hyperlaxity of distal joints. Decreased fetal movements are frequently reported. Some affected children acquire the ability to walk independently; however, progression of the disease results in a loss of ambulation by age ten to eleven years. Early and severe respiratory insufficiency occurs in all individuals, resulting in the need for nocturnal noninvasive ventilation (NIV) in the form of bilevel positive airway pressure (BiPAP) by age 11 years. Intermediate COL6-RD is characterized by independent ambulation past age 11 years and respiratory insufficiency that is later in onset than in UCMD and results in the need for NIV in the form of BiPAP by the late teens to early 20s. In contrast to individuals with Bethlem muscular dystrophy, those with intermediate COL6-RD typically do not achieve the ability to run, jump, or climb stairs without use of a railing. [from GeneReviews]

Ullrich congenital muscular dystrophy-1 (UCMD1) 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). For general phenotypic information and a discussion of genetic heterogeneity of Ullrich congenital muscular dystrophy, see UCMD1A (254090). [from OMIM]

A decreased amount of collagen VI in muscle tissue. Collagen VI is a primarily associated with the extracellular matrix of skeletal muscle. [from HPO]