Skeletal Muscle Involvement in Wilson Disease: Clinical and Magnetic Resonance Imaging (MRI) Observations in 2 Families

Objective: Skeletal muscle involvement in Wilson disease is rare. Calf muscle pain might be attributed as growing pain in children. We report calf muscle involvement in Wilson disease and describe the magnetic resonance imaging (MRI) findings of leg, differential diagnosis with literature review.

Patients and methods: Our observations describe calf muscle MRI abnormality in 5 cases of Wilson disease from 2 families. The clinical presentations were neurologic in 3, hepatic in 1, and asymptomatic in 1 patient. We systematically describe the clinical characteristics and their calf muscle MRI findings.

Results: Three patients had bilateral calf pain and intermittent cramps. The pain was of mild to moderate intensity and managed symptomatically. Serum alkaline phosphatase, creatinine phosphokinase, and needle electromyography were normal. Turbo inversion recovery magnitude sequence MRI of calf muscle revealed hyperintensity in bilateral gastrocnemii muscles. These muscles appear hyperintense in diffusion-weighted imaging.

Conclusion: The calf muscle involvement could be attributed to muscle edema due to copper-induced muscle toxicity mediated by inhibition of Na⁺/K⁺-ATPase on cellular membranes of fast-twitch gastrocnemii muscles which contain predominant type II myofiber. In Wilson disease patients with calf pain or cramps, muscle MRI may show nonspecific gastrocnemius hyperintensity. Further evaluation may give insight into its pathophysiology.

Keywords: K-F ring; TIRM; calf muscle; cramps; gastrocnemii; hyperintensity.