Which muscular dystrophy is commonly associated with early-onset cataracts and distal involvement in some forms?

• A. Myotonic dystrophy type 1
• B. Duchenne muscular dystrophy
• C. Becker muscular dystrophy
• D. Pompe disease

Answer: (A)

Early cataracts combined with distal muscle weakness are classic cues for myotonic dystrophy type 1. This condition is a multisystem muscular dystrophy caused by a CTG repeat expansion in the DMPK gene, and it often presents with myotonia (delayed muscle relaxation), facial weakness, and weakness starting in the distal muscles of the limbs. Cataracts can appear early, even in childhood, which makes this pattern distinctive.

In contrast, Duchenne and Becker muscular dystrophies are dystrophinopathies that mainly cause proximal weakness (in the hips, shoulders, and thigh muscles) with calf pseudohypertrophy and early cardiopulmonary issues, but not early cataracts. Pompe disease presents with proximal muscle weakness and often cardiomyopathy, without the characteristic early eye changes.