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A new study suggests that the body’s inability to fully utilize the essential dietary mineral manganese might be to blame for some cases of severe scoliosis. Researchers at Washington University School of Medicine in St. Louis have found that children with severe scoliosis are twice as likely as children without the disease to carry a gene variant that makes it hard for their cells to take in and use manganese. Manganese is required for growing bones and cartilage.
About 3 million new cases of scoliosis are diagnosed every year. Most are mild and require only that doctors keep a watchful eye on the condition. Children who develop a moderate bend to their spine may need to wear a back brace until they finish growing. In rare cases, the curvature is so pronounced that it requires surgery to correct.
Cases of scoliosis tend to cluster in families, but not in a simple way, which suggests that many different genes each play a small role in increasing the risk of the disease. To identify such genes, researchers scanned all the genes in 457 children with severe scoliosis and 987 children without scoliosis.
They found a variant in the gene SLC39A8 in only 6 percent of the healthy children but 12 percent of the children with severe scoliosis. A second analysis in a separate group of 1,095 healthy children and 841 children with moderate to severe scoliosis also found that children with scoliosis were about twice as likely to carry the variant.
When the researchers bred zebrafish with a disabled SLC39A8 gene, the fish developed movement and skeletal abnormalities, including curves in their spines. The gene helps cells take in minerals such as zinc, iron and manganese. Human cells with the gene variant successfully took up zinc and iron but failed to take in manganese. They also discovered that children with the gene variant had significantly lower levels of manganese in their blood than those with the more common form-although both groups were still within the normal range.
Manganese is both an essential mineral and a toxin. High doses can cause manganism, a permanent neurological condition characterized by tremors and difficulty walking, as well as psychiatric symptoms such as aggression and hallucinations. The mineral also has been linked to Parkinson’s disease, schizophrenia and high blood pressure.
Too little manganese, on the other hand, can cause manganese deficiency, although this is rarely seen in people because the human body needs only trace amounts that are easily obtained from food. Animal studies show that lack of manganese can result in problems metabolizing fat and sugar, impaired growth, difficulty walking and curvature of the spine. The children with the genetic variant did not have manganese deficiency, but they may be unable to use manganese as efficiently as others.