NORD gratefully acknowledges Barry S. Russman, MD, Professor of Pediatrics and Neurology, Oregon Health Sciences University and Shriners Hospital for Children-Portland, for assistance in the preparation of this report.
Kugelberg Welander syndrome is a milder type of spinal muscular atrophy. It is a rare inherited neuromuscular disorder characterized by wasting and weakness in the muscles of the arms and legs, leading to walking difficulties in, and eventual loss of ambulation. Symptoms of Kugelberg Welander syndrome occur after 12 months of age. Patients learn to walk, may fall frequently and may have trouble walking up and down stairs at 2-3 years of age; some patients will not show functional changes until the teens. The legs are more severely affected than the arms. The long-term prognosis depends on the degree of motor function attained as a child.
Kugelberg Welander syndrome is inherited as an autosomal recessive trait. Molecular genetic testing has revealed that all types of autosomal recessive SMA (Werndnig-Hoffman disease, juvenile SMA and Kugelberg-Welander disease) are caused by mutations in the SMN (survival motor neuron) gene on chromosome 5. Deletion of the NAIP (neuronal apoptosis inhibitory protein) gene that is close to the SMN gene is also associated with SMA. More patients with Werdnig Hoffman disease (SMA1) than other types of SMA have NAIP deletions. The relationship between specific mutations in the SMN gene and nearby genes and the severity of SMA is still being investigated so classification of SMA subdivisions is based on age of onset of symptoms and maximum function achieved as opposed to the genetic profile.
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