Diagnosis:
Clinical features consistent with statin myopathy, exclusion of other causes and improvement of myopathy on discontinuation of statin. Antibody tests can be useful in distinguishig between statin induced necrotizing myopathy and necrotizing autoimmune myopathy.
Clinical features:
Proximal symmetric muscle weakness, usually spares the face, bulbar muscles and sphincters
CK: usually elevated, may be normal
+Muscle biopsy:
Fibre size variation, atrophic rounded fibres
Necrotic fibres, regenerating fibres,
No inflammation
In some mitochondrial features: ragged red fibres, COX deficient fibres, lipid excess
Genetics:
Associated with polymorphism in SLCO1B1 gene, organic-anion transporting polypeptide OATP1B1, C allele of the rs4149056 polymorphism.
Antibodies:
Anti-HMGCR Abs (3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase): associated with necrotizing autoimmune myopathy
Related articles:
References:
- SEARCH Collaborative Group, Link E, Parish S, Armitage J, Bowman L, Heath S, Matsuda F, Gut I, Lathrop M, Collins R. SLCO1B1 variants and statin-induced myopathy–a genomewide study. N Engl J Med. 2008 Aug 21;359(8):789-99. doi: 10.1056/NEJMoa0801936. Epub 2008 Jul 23.
- Allenbach Y, Drouot L, Rigolet A, Charuel JL, Jouen F, Romero NB, Maisonobe T, Dubourg O, Behin A, Laforet P, Stojkovic T, Eymard B, Costedoat-Chalumeau N, Campana-Salort E, Tournadre A, Musset L, Bader-Meunier B, Kone-Paut I, Sibilia J, Servais L, Fain O, Larroche C, Diot E, Terrier B, De Paz R, Dossier A, Menard D, Morati C, Roux M, Ferrer X, Martinet J, Besnard S, Bellance R, Cacoub P, Arnaud L, Grosbois B, Herson S, Boyer O, Benveniste O; French Myositis Network. Anti-HMGCR autoantibodies in European patients with autoimmune necrotizing myopathies: inconstant exposure to statin. Medicine (Baltimore). 2014 May;93(3):150-7. doi: 10.1097/MD.0000000000000028.
- Mohassel P, Mammen AL. Statin-associated autoimmune myopathy and anti-HMGCR autoantibodies. Muscle Nerve. 2013 Oct;48(4):477-83. doi: 10.1002/mus.23854. Epub 2013 Aug 30.