Necrotizing Autoimmune Myopathy NAM

Diseases,

Diagnosis:

Clinical features plus positive antibodies and usually with necrotizing myopathy on biopsy

Clinical features:

Age range 30-60, progressive myopathy with profound proximal muscle weakness. May also occur in patients recieving statins, but most patients are statin naive

Antibodies:

Positive antibodies Anti-HMGCR Abs (3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase)

Muscle biopsy:

H&E: Necrotic fibers with a few regenerating fibres. Some macrophage infiltration can occur but typically no lymphocytic infiltration.
Immunohistochemistry:

  • major histocompatibility complex class I demonstrates macrophages as part of myophagocytosis but no upregulation in un-invovled muscles fibres
  • Complement: no deposition in microvasculature
  • CD3: no T cells

Treatment:

Corticosteroids
Consider other immunotherapy

Related articles:

References:

  1. Ramanathan S, Langguth D, Hardy TA, et al. Clinical course and treatment of anti-HMGCR antibody–associated necrotizing autoimmune myopathy. Neurology® Neuroimmunology & Neuroinflammation. 2015;2(3):e96. doi:10.1212/NXI.0000000000000096.
  2. 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.
  3. 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.