Myotonic dystrophy is a multisystemic disorder affecting the skeletal muscle. Male patients have an increased risk of fractures and develop a number of endocrine/metabolic impairments known to adversely affect bone health.

The goal of a recent study published in Neuromuscular Disorders was to determine the occurrence of fragility fractures and the bone mineralization status—lumbar spine, hip and total body—by dual X-ray absorptiometry.

This study enrolled 36 male patients affected with type 1 myotonic dystrophy and 13 affected with type 2 myotonic dystrophy.

Fragility fractures were recorded in 15 type 1 and 7 type 2 myotonic dystrophy in non-classical osteoporotic sites, such as metatarses. While hip osteopenia was the most frequent finding, particularly in type 2 than type 1 myotonic dystrophy patients; osteoporosis was rare. On the other hand, patients with type 1 myotonic dystrophy presented higher total body bone mass density than patients with type 2 myotonic dystrophy and healthy controls. Lumbar spine was positively associated with the severity of the disease. Furthermore, gonadic failure, with low testosterone and reduced INSL3 levels, visceral adiposity and insulin resistance correlated with reduced body mass index in both type 1 and type 2 myotonic dystrophic patients.

The results indicated that independent determinants of fragility fractures were low total body mass index, low blood testosterone and low global muscle mass.

Source: Neuromuscular Disorders. 2019 Nov 20. pii: S0960-8966(19)31202-7. doi: 10.1016/j.nmd.2019.11.006.