Woman with unsteady walk is diagnosed with SMA in her late 40s

Margarida Maia PhD avatar

by Margarida Maia PhD |

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A woman with a long history of muscle weakness was found to have spinal muscular atrophy (SMA) in the her late 40s, a diagnosis that was prompted by her unsteady walk and records that showed her parents were blood relatives, a case report indicates.

“There are few cases reported of SMA being diagnosed this late in a person’s life,” the researchers wrote in “An Insightful Observation Leading to a Late Diagnosis of Spinal Muscular Atrophy: A Case Report,” which was published in Cureus. “We believe that highlighting the importance of clinically being able to identify the disease as early as possible may aid in modifying the progression of the disease course as well as reducing the morbidity [symptoms] and mortality associated with it.”

SMA is nearly always caused by mutations in the SMN1 gene and a shortage of the SMN protein. Without enough of it, motor neurons, the nerve cells that communicate with muscles to control voluntary movements, lose function and die. There are several different types of SMA, which start at different ages. Usually, “the severity of the disease is inversely related to the age of onset; that is to say, the earlier the onset of symptoms, the more severe the disease course,” the researchers wrote.

When SMA manifests in adulthood, symptoms are usually mild and progress slowly without shortening the person’s lifespan. These may include difficulty walking or weakness in the hands and feet. While it’s rare, the disease may go undiagnosed until late in adulthood.

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Here, researchers in the Antillean islands of Puerto Rico, Saint Kitts, and Nevis describe the case of a 47-year-old woman who was seen for anemia, or low numbers of red blood cells, that occurred secondary to chronic kidney disease.

A review of the woman’s medical records showed her parents were related by blood and that she had been treated with corticosteroids for many years, “as long as she could recall,” for an unspecified progressive muscle weakness.

During one visit, doctors noticed she walked unsteadily, with an ataxic gait. This, along with the fact that her parents were related, caused the doctors to suggest she have a genetic test, which revealed a disease-causing mutation in one copy of the SMN1 gene. Based on these findings, the doctors made a diagnosis of SMA. The woman “was referred for genetic counseling, where she was informed about her condition and the risk of progression,” the researchers wrote.

“We have successfully confirmed the diagnosis of a patient with an SMA that had remained undiagnosed for the better part of 40 years,” they wrote. “Diagnosing this disease proves to be somewhat difficult due to its many nonspecific clinical manifestations, such as progressive muscle weakness, ataxic gait, and muscle loss.”

The woman’s children were also found to carry the same gene mutation as their mother. While they didn’t show symptoms of the disease, the researchers “urge clinicians to perform genetic testing when clinical suspicion points to SMA to ensure timely and accurate diagnosis.”

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