• lipid-storage disease
• riboflavin
• muscle disease

A 38-year-old woman gave a 1-year history of difficulties climbing stairs and walking long distances, needing a wheelchair at times. More recently, she had also experienced weakness of her arms with difficulties doing her hair or lifting light weights. She reported shortness of breath on mild exertion and had lost 12 pounds in weight because of muscle loss. She had no muscle pain, episodes of dark urine, muscle twitching, visual disturbances, hearing loss, speech difficulties, dysphagia, numbness or tingling, bladder or bowel difficulties, fevers, rash or joint pain. She had met all milestones at a normal age and had normal development.

Her medical history was unremarkable. She had not taken any lipid-lowering agents and there was no illicit drug use or toxic exposure. There was no relevant family history and no consanguinity.

On examination, she showed bilateral and symmetric scapular winging. There was no percussion or action myotonia or paramyotonia, and no fasciculations. Her muscle bulk and tone were normal. Cranial nerves were all normal. Manual muscle strength testing showed the following Medical Research Council (MRC) grades (right/left where applicable): neck flexion 4–, neck extension 5, shoulder abduction 4/4, external rotation of elbow 4/4, elbow flexion 4/4, elbow extension 4+/4+, wrist flexion 5/5, wrist extension 5/5, finger flexion 5/5, finger extension 5/5, hip flexion 4/4, hip extension 3/3, hip abduction 3/3, knee extension 4+/4+, knee flexion 4/4, ankle dorsiflexion 5/5 and ankle plantar flexion 5/5. Deep tendon reflexes were 1+ at triceps, brachioradialis and ankles, and 2+ at biceps and knees bilaterally. She had a waddling gait. Plantar responses were flexor. Sensory and coordination exams were normal.