Congenital fiber type disproportion (CFTD) is a rare genetic muscle disease that is usually apparent at birth (congenital myopathy). It belongs to a group of muscle conditions called the congenital myopathies that tend to affect people in a similar pattern.
Major symptoms may include loss of muscle tone (hypotonia) and generalized muscle weakness. Affected infants may also have distinctive facial features. Additional common symptoms that occur include abnormal side-to-side curvature of the spine (scoliosis), delays in motor development, dislocated hips, and the permanent fixation of certain joints in a flexed position (contractures).
Most patients with CFTD have no other affected relatives (sporadic). Some cases are inherited as an autosomal recessive or dominant trait. In one family, CFTD was inherited as an X-linked recessive trait.
The diagnosis of congenital fiber type disproportion is controversial. The changes to muscle tissue that characterize the disorder can also occur in association with many other disorders or conditions including other congenital muscle disorders, Krabbe disease, Lowe’s syndrome, myotonic dystrophy, fetal alcohol syndrome, and a variety of brain malformations such as cerebellar hypoplasia. These conditions should be excluded before a diagnosis of CFTD is made.
The prognosis is relatively favorable in most patients. However, there are cases in which the same histological features are associated with slowly progressive weakness from childhood, rigid spine syndrome, or severe and progressive motor involvement with kyphoscoliosis and respiratory insufficiency.
Treatment of Congenital fiber type disproportion may consist of active and passive exercises and physical therapy to promote muscle function. Functional improvement usually occurs as the patient matures. Genetic counseling may be of benefit for patients and their families. Other treatment is symptomatic and supportive.