Ullrich congenital muscular dystrophy (UCMD) is a rare hereditary muscle condition that manifests at birth or a few months after birth. It belongs to a group of disorders called collagen type 6-related myopathies and characterized by abnormalities in collagen type 6, a major protein that supports skeletal muscles.
Collagen type 6 is made up of six interlinked protein chains called alpha chains. Each chain has to be formed and function correctly for the protein to function properly. The COL6A1, COL6A2, and COL6A3 genes carry instructions to make the alpha chain 1, 2, and 3, respectively; a mutation in any one of the genes can lead to the production of a faulty collagen type 6 protein.
Collagen type 6 is one of the main components of the matrix between muscle cells and connective tissue. It provides stability to the muscle cells and supports their growth. Any issues with collagen type 6 will result in an unstable matrix and affect the stability of the surrounding muscles, which causes progressive muscle weakness.
UCMD is characterized by generalized muscle weakness and excessively high range of motion (hypermobility) in the finger joints and wrist. Other symptoms include:
- less movement at birth
- low muscle tone or floppiness (hypotonia)
- a tilted head (torticollis)
- poor head control
- tightness in the hip, knees, and elbows (congenital contractures)
- abnormal curvature of the spine (scoliosis)
Symptoms vary from patient to patient. In some cases, there may be reduced fetal movement, while in others first symptoms may not be obvious until a few months after birth. Delay in unaided sitting, crawling, or walking may indicate UCMD.
The signs and symptoms of UCMD often are similar to those of other types of collagen type 6-related muscular dystrophies. There also is an overlap in the causes of the multiple forms of these conditions, making it difficult to reach a diagnosis.
Imaging tests, such as magnetic resonance imaging, of the muscles may provide insight into muscle involvement and help diagnose UCMD.
Muscle biopsy is a more invasive technique to detect signs of muscular dystrophy. A small piece of muscle is surgically removed and observed under the microscope for any changes in, or absence of, collagen type 6. Because collagen type 6 also is found on the skin, a skin biopsy may be performed.
Genetic testing is the most accurate diagnostic tool for conditions caused by genetic mutations. It can identify mutations in collagen type 6 genes to confirm the diagnosis. It can be performed as a prenatal test, or after birth once the symptoms appear.
UCMD is mostly inherited in an autosomal recessive manner, meaning that for a child to develop the disease he must have inherited two faulty copies of the causative gene, one from each parent. In rare cases, the disease also can be inherited in an autosomal dominant manner, where one faulty copy of the gene inherited from only one parent is sufficient to cause the condition. For families with a history of UCMD, in-vitro fertilization with pre-implantation genetic diagnosis is an option in which the embryos can be prescreened for the mutations before being implanted into the mother’s womb.
There currently is no cure for UCMD and treatments focus on managing the symptoms of the disease. For example, regular stretching and movement under the guidance of a trained physiotherapist can help slow muscle weakness. Use of assistive aids such as splints, crutches, and wheelchairs also can help improve mobility.
Some UCMD patients may have feeding difficulties such as taking a long time to finish eating or difficulty swallowing food due to muscle weakness. That can manifest as failure to thrive (the inability to gain weight or sudden weight loss). It also can cause nutritional deficits. Consultation with a trained nutritionist can help plan meals to increase energy intake. In severe cases, gastrostomy, or the surgical insertion of a feeding tube through the skin into the stomach, may be required to boost weight gain.
Respiratory problems may occur in UCMD patients. Antibiotics are prescribed in case of respiratory infections. During severe episodes of respiratory distress, supplemental oxygen and/or ventilation support may be necessary to help patients breathe. Cough medicines and bronchodilators may be prescribed to help cough up mucus and clear the airways.
In cases of scoliosis and contractures, surgery may be required to correct the defect.
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