Congenital myotonic dystrophies are a group of rare genetic disorders characterized by muscle weakness and prolonged muscle contractions, known as myotonia, that are present from birth. These conditions belong to a larger category of muscular dystrophies, which are progressive muscle disorders resulting from abnormalities in certain genes.
There are two main types of congenital myotonic dystrophies: type 1 and type 2, both of which are inherited in an autosomal dominant manner. Type 1, also known as myotonic dystrophy type 1 (DM1) or Steinert's disease, is caused by a mutation in the DMPK gene. Type 2, also called myotonic dystrophy type 2 (DM2), is associated with a mutation in the CNBP gene.
Common symptoms of congenital myotonic dystrophies include muscle weakness in the face, limbs, and respiratory muscles, delayed motor development, impaired muscle relaxation (myotonia), feeding difficulties in infants, and intellectual and cognitive impairment in some individuals. Additionally, affected individuals may exhibit other associated features, such as cataracts, cardiac abnormalities, and endocrine disturbances.
Diagnosis of congenital myotonic dystrophies often involves a combination of clinical evaluation, genetic testing, electromyography (EMG), and muscle biopsies. Treatment primarily focuses on managing symptoms and addressing complications. This may involve physical therapy to maintain muscle strength and flexibility, occupational therapy to improve functional abilities, and respiratory support if breathing difficulties arise. Additionally, regular monitoring of cardiac and other affected systems may be required.
Due to the genetic nature of congenital myotonic dystrophies, genetic counseling is essential for affected individuals and their families to understand the inheritance pattern and potential risks for future generations
