Distal myopathy in multi-minicore disease

Area of Science:

• Neurology
• Genetics
• Muscle Biology

Background:

• Distal myopathies are a heterogeneous group of inherited muscle disorders.
• Muscle imaging and biopsy are crucial for diagnosis.
• Genetic mutations are often identified in specific myopathy-related genes.

Observation:

• A 52-year-old man presented with progressive distal muscle weakness starting at age 36.
• Muscle CT showed fat replacement in type 1 predominant muscles (soleus, anterior tibial, paraspinal) with relative sparing of others.
• Muscle biopsy revealed multi-minicores in approximately 70% of type 1 fibers.

Findings:

• A novel heterozygous RYR1 gene variant (c.5869T > A, p.S1957T) was identified.
• This variant was absent in 100 control DNA samples.
• Mutations in known multi-minicore disease and distal myopathy genes were excluded.

Implications:

• This case likely represents a unique distal myopathy subtype.
• The findings highlight RYR1 as a potential gene involved in this specific myopathy.
• Preferential involvement of type 1 muscle fibers is a key characteristic.