Osteoporosis, osteopenia appear common in Friedreich's ataxia



SYDNEY, AUSTRALIA – Friedreich’s ataxia patients may be at greater risk of osteopenia and osteoporotic fractures, according to a study showing significant decreases in bone mineral density at key sites such as the femoral neck.

Data presented in a poster at the international congress of Parkinson’s Disease and Movement Disorders also showed a correlation between Friedreich’s ataxia disease severity measures and bone mineral density measures.

Dr. Wolfgang Nachbauer

Dr. Wolfgang Nachbauer of the department of neurology at Innsbruck (Austria) Medical University and his colleagues measured bone mineral density of the femur, lumbar vertebral column, radius, and ulna, using dual-energy x-ray absorptiometry in 20 patients with Friedreich’s ataxia. Mean age of the patients was 39.4 years.

They found 45% of patients (9 of 20) had osteoporosis at the femur, and 20% (4 of 20) had osteopenia at the same site, while bone mineral density measurements of the lumbar vertebral column showed osteopenia in 30% (6 of 20) and osteoporosis in 10% (2 of 20). Seven patients (35%) had osteopenia in the forearm.

Dr. Nachbauer said this was the first study exploring the incidence of osteopenia and osteoporosis in patients with this disorder.

"We observed clinically some pathological fractures within our Friedreich’s ataxia patients and together with the known action of the iron metabolism it made us think there could be an increased prevalence of osteoporosis and osteopenia with Friedreich’s ataxia," Dr. Nachbauer said in an interview.

Friedreich’s ataxia is a neurodegenerative disorder caused by a mutation in the frataxin gene, which codes for a protein involved in mitochondrial oxidative metabolism and iron homeostasis. Nonneurologic manifestations of Friedreich’s ataxia include scoliosis and foot deformities.

The study found that the most significant decreases in bone mineral density were at the femoral neck site, which is also a common site for hip fracture.

The researchers also examined the correlation between degree of bone mineral density loss and clinical indicators of disease severity in Friedreich’s ataxia. They found a significant, negative association between bone mineral density measurements at the femoral neck and scores on the Scale for the Assessment and Rating of Ataxia (SARA) and the length of GAA allele repeats in the frataxin gene – the defining feature of Friedreich’s ataxia.

"We also used the FRAX score, which is the score for the risk of pathological fractures within the next 10 years and also this score was increased in Friedreich’s ataxia patients," Dr. Nachbauer said.

While there were no significant interactions between potential confounders such as age and body mass index, the study found that wheelchair-bound patients had significantly lower bone density, compared with mobile patients.

The findings offer an opportunity for early intervention to address what may be a significant comorbidity associated with Friedreich’s ataxia.

"Densitometry on a routine basis should therefore be included in the management of [Friedreich’s ataxia] patients [as] initiation of medical therapy may prevent osteoporosis-related fractures," the researchers said.

No conflicts of interest associated with the study were declared.

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