Diagnosis and Testing
How do I get tested for Bethlem myopathy?
There are multiple ways to be tested for Bethlem myopathy. Bethlem myopathy is typically suspected based off of physical signs and symptoms. These people typically will have proximal muscle weakness (muscle weakness that of or near the torso) and contractures (stiffness of joints causing limited mobility) most commonly of the long fingers, elbows, and ankles. Bethlem myopathy may be tested by blood tests for an enzyme called creatine kinase that leaks from the muscles when muscles are breaking down, muscle MRI, muscle or skin biopsy, or genetic testing. Typically, doctors order the least invasive tests first to look for a diagnosis before ordering more invasive testing.
Creatine kinase levels are usually normal or slightly elevated in people who have Bethlem myopathy. Creatine kinase is an enzyme that leaks from the muscles when they break down. Muscle MRI of the thigh or calf muscles may be performed. For affected individuals, the MRI will show differences in the vasti muscles, which are muscles in the thigh, and the calf muscles. If a muscle biopsy is performed, the results will show what is called myopathic or dystrophic changes. Testing to look specifically for collagen VI in the muscles is typically normal or only slightly abnormal. Testing to look for collagen VI activity on skin cells is typically abnormal and indicates that the person is affected with Bethlem myopathy. Genetic testing can also be performed, which will look for any genetic changes in the COL6A1, COL6A2, and COL6A3 genes.
SOURCE: Emory University - Department of Human Genetics in collaboration with ThinkGenetic • https://www.thinkgenetic.com/diseases/bethlem-myopathy-109941/diagnosis-testing/67031 • DATE UPDATED: 2019-02-22
Genetics home reference, Collagen VI-related myopathy, https://ghr.nlm.nih.gov/condition/collagen-vi-related-myopathy Accessed 21FEB19
Lampe AK, Flanigan KM, Bushby KM, et al. Collagen Type VI-Related Disorders. 2004 Jun 25 [Updated 2012 Aug 9]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2019.Available from: https://www.ncbi.nlm.nih.gov/books/NBK1503/