distal myopathy with posterior leg and anterior hand involvement

Distal myopathy with posterior leg and anterior hand involvement is a neuromuscular condition characterized by progressive and symmetric muscle weakness affecting the muscles of the anterior upper limbs and posterior lower limbs. It is associated with pathogenic variants in the FLNC gene, which plays a crucial role in muscle structure and function. Inheritance is autosomal dominant, meaning that affected individuals have a 50% chance of passing the condition on to their children. The condition is very rare, affecting fewer than 1 in 1,000,000 people.

Individuals with this condition typically experience muscle-related symptoms. Characteristic features include exercise-induced myalgia and intrinsic hand muscle atrophy, which are reported in a high percentage of cases. Many patients also face significant challenges such as hyporeflexia of the lower limbs, gait disturbances, and even an inability to walk in more severe presentations. Less common features such as foot dorsiflexor weakness, difficulty running, and limited knee flexion emerge over time. Not all individuals experience every symptom, and the severity and progression can vary considerably.

This condition is caused by pathogenic variants in the FLNC gene, which encodes filamin C, a protein critical for maintaining the integrity and function of muscle fibers. It is inherited in an autosomal dominant pattern, meaning that having one altered copy of the gene is sufficient to cause the disorder. As a result, an affected individual has a 50% risk of passing the variant to their offspring. That not all individuals who inherit the variant experience every symptom, reflecting variable expressivity.

Currently, management focuses on supportive care and symptom management, as there are no FDA-approved or foundational therapies specifically linked to this condition. Treatment is tailored to the individual and typically involves a multidisciplinary team that may include physical therapists, occupational therapists, and other specialists. Regular surveillance is an essential part of long-term care, helping to identify potential complications early. Genetic counseling is recommended to assist families in understanding the inheritance pattern and to discuss family planning options.

The clinical course of distal myopathy with posterior leg and anterior hand involvement varies widely among affected individuals. With current standards of care and a multidisciplinary approach, many individuals maintain a good quality of life well into adulthood despite progressive muscle weakness. Outcomes described in medical literature continue to evolve as standards of care improve, and the condition may progress, stabilize, or show variable patterns in different individuals. Families often find it helpful to connect with specialists familiar with neuromuscular disorders for ongoing management and support.