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.
The following resource from Cure SMA provides a description of symptoms, as well as videos to assist with early diagnosis:
People with Kugelberg Welander syndrome experience muscle wasting, difficulty in walking or climbing stairs, and trouble rising from lying on one’s back. Breathing may be affected, but very late in the course of disease. Approximately 50% of patients with Kugelberg Welander syndrome develop spinal curvature (scoliosis).
All types of proximal spinal muscular atrophy (SMA) including Kugelberg Welander syndrome are caused by mutations in the SMN (survival motor neuron) gene at chromosomal locus 5q11-q13. 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.
Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosomal locus 5q11-q13” refers to bands 11-13 on the long arm of chromosome 5, the area where the SMA gene sits. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
Spinal muscular atrophy is inherited in an autosomal recessive manner. Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.
The birth prevalence of all types of spinal muscular atrophy has been estimated to be 7.8 per 100,000 live births. An estimate of the prevalence of Kugelberg-Welander syndrome (SMA3) is not available.
Molecular genetic testing is used to determine if a mutation is present in the SMN gene. SMA is caused by a partial or complete loss of the SMN gene and about 95% of those affected will show a deletion of both copies of a specific portion (exon 7 or exon 8) of the gene. About 5% of those affected will show a deletion of exon 7 in one copy of the SMN gene and a different mutation in the other copy of the SMN gene.
Prior to the availability of molecular testing, neurophysiologic studies and muscle biopsy were used for diagnosis, but these tests are no longer necessary unless SMN gene testing is normal.
Carrier testing for SMA is a molecular genetic test in which the number of copies of the SMN gene in which exons 7 and 8 are present is determined.
Treatment of Kugelberg-Welander syndrome is aimed at alleviating the symptoms. In most cases physical therapy and orthopedic devices may be prescribed. Ventilation support may be used to assist breathing. An orthopedic appliance may be used to allow the patient to be upright when scoliosis becomes a major problem. Surgery is necessary when spinal curvature becomes severe (more than 50 degrees).
In 2017, Spinraza (nusinersen) was FDA approved as the first drug to treat children and adults with SMA. Spinraza is manufactured by Biogen.
Genetic counseling may be of benefit for patients and their families. Other treatment is symptomatic and supportive.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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Some current clinical trials also are posted on the following page on the NORD website:
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