• Researchers studied bone mineral density (BMD) — the amount of calcium, phosphorus, and other minerals in the bones — in children with spinal muscular atrophy (SMA).
• Two-thirds of the children in the study had low BMD, and one child had osteoporosis, showing that SMA can put children at risk for bone problems.

A new study, published in August in the journal BMC Musculoskeletal Disorders, shows that children with SMA may be at risk for weakened bones.

SMA causes muscle weakness, and people with the condition often lose mobility over time. These factors make it harder for the bones to stay strong. Some past research has found that people with SMA are more likely to have bone problems such as fractures.

In the new study, set in China, researchers analyzed BMD in 22 children with SMA type 2 and 18 children with SMA type 3. The average age of all of the children in the study was 5.5 years old.

To measure BMD levels, the study authors used an imaging test called dual-energy X-ray absorptiometry (DXA). DXA scans use a tiny amount of radiation to detect the amount of minerals in the bones. Bones store minerals like calcium and phosphorus, which help keep the bones strong.

The researchers found that 67.5 percent of the children in the study had low BMD. Those with SMA type 2 had lower BMD levels than children with SMA type 3. Additionally, 37.5 percent of the study participants had low levels of vitamin D, which the body needs in order to absorb calcium. One child was diagnosed with osteoporosis, a disease in which a person has very weak bones.

The authors concluded that children with SMA types 2 and 3 were at risk for weakened or broken bones. “Regular monitoring of BMD by DXA scan and taking active interventions aimed at SMA children with different types are important,” the authors wrote.