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Acquired rippling muscle disease in association with myasthenia gravis

We present a case of acquired rippling muscle disease associated with myasthenia gravis and a unique combination of physical signs and muscle biopsy findings.

Rippling muscle disease (RMD) is a rare and generally benign myopathy characterised by muscle stiffness, muscle hypertrophy and self-propagating rippling of muscles induced by stretch or percussion.1 Myoedema, percussion induced rapid contraction and 3–25- fold elevation of serum creatine kinase (CK) levels are also typical features.

RMD occurs in genetic and sporadic forms. The autosomal dominant genetic form includes two distinct loci: the caveolin-3 gene and an undefined locus at 1q41–q42.2 Caveolin-3 gene mutations are also seen in patients with limb girdle muscular dystrophy 1C, distal myopathy and idiopathic hyperCKaemia. An autosomal recessive form also exists.3 Sporadic RMD is thought to be immune mediated.4 5 6 There are four case reports of acquired RMD in association with myasthenia gravis (RMD-MG) (ie, eight patients in total with RMD-MG since the first reported case in 1996).4 5 6 7 We …