Late onset nemaline myopathy (LONM) is a rare genetic neuromuscular disorder characterized by a delayed presentation of symptoms related to muscle weakness and progressive muscle deterioration. It falls under the broader classification of nemaline myopathies, a group of disorders characterized by the presence of thread-like structures called nemaline rods within muscle fibers.
LONM specifically refers to a form of nemaline myopathy where symptoms typically manifest in adulthood, usually beyond the age of 18. Individuals affected by LONM often experience generalized muscle weakness and atrophy, predominantly affecting the proximal muscles (such as those in the hips, thighs, shoulders, and upper arms). This can lead to difficulties in performing daily activities, including standing, walking, and lifting objects. Additional symptoms may include respiratory problems, such as shortness of breath and respiratory muscle weakness.
Genetic mutations are responsible for the development of LONM, typically affecting genes involved in skeletal muscle structure and function. The precise inheritance pattern of LONM is not fully understood, as both recessive and dominant forms have been described.
Diagnosis of LONM often involves a combination of clinical evaluation, electromyography, muscle biopsies, and genetic testing. Although there is no known cure for LONM, management strategies include physical therapy to maintain muscle strength and mobility, and respiratory support if necessary. The prognosis for individuals with LONM varies, with some cases being relatively stable or slowly progressing, while others may lead to significant disability and decreased life expectancy.
