MLIP-associated myopathy; report of a patient and review of the literature

Objective: Biallelic variants in the MLIP gene have been recently described as a novel cause of rhabdomyolysis. Here we are reporting a patient with biallelic variant in the MLIP gene causing characteristics clinical features.

Case description: Thirteen-year-old male with uneventful perinatal history and normal early development presented initially at 5-year old, with history of muscle cramps in the legs started at the age of 2-year. This cramp localized into the calf muscles and alternated between the two legs. This cramps usually lasts for 5-minutes. These episodes of cramps are usually triggered by intense or prolonged exercises or lifting heavy objects. Thes are usually associated with muscle ache that got relieved by rest. Patient had normal exam interictally. Patient had elevated createnine phosphokinase (CPK) with value fluctuated between 4000 – 8000 Unit/ Litter. He had muscle biopsy performed from the left quadriceps and showed mild myopathic changes in H &E. Electron microscopy (EM) showed aggregation of glycogen granules were seen in moderate number of fibers. Patient was found to have homozygous variant in MLIP gene at 1696C>T (p.Gln566Ter) and both parents were heterozygous for the same variant.

Conclusion: MLIP-associated myopathy is a novel myopathy characterized by recurrent episodes of rhabdomyolysis, muscle ache, mild muscle weakness and occasional cardiac involvement. Further studies are required to understand the precise function of this protein and the pathogenesis mechanism in this novel myopathy, muscle biopsy findings and the natural history of patients with this novel myopathy.
Keywords: MLIP, myopathy, rhabdomyolysis