Keywords for Investigation, Referral and writing hospital charts by Myositis 5/5 (8)

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ICD-10 codes

 The diagnosis is based on

  • Disease history
    • Muscles
    • Skin
    • Lungs
  • Investigation findings (including CK)
  • Exclude another disease (differential diagnoses)

Disease history / Symptoms

  • First-degree family (parents, siblings or children) with muscular disease: Exclusion Muscular Dystrophy?
  • Debut of muscle symptoms
    • Time and what muscle groups: proximal / distal, thigh, neck
    • Previous new medication with statins, anabolic steroids, drugs or something else?

* (Star) indicates data included in classification criteria:


  • * Symmetrical weakness in proximal muscle groups (classical)
  • Atrophy symmetrically, proximal / distal in muscles
  • Swallowing Function:
  • Signs of reduced heart muscle function? (myocarditis)
  • Muscle pain (at 40%)
  • * Elevated CK, maximum CK value (400-30.000?)

Immunosuppressive treatment

  • Prednisolone, MTX, Mycophenolate (CellCept), Imurel, Ciclosporin, Tacrolimus, Rituximab, Cyclophosphamide, Immunoglobulin.
  • Statins


  • Tobacco (yes, not, previously)
  • Alcohol
  • Other drugs (Cocaine with more)

Investigations / Investigation

  • Clinical examination


  • Muscle atrophy
    • Proximal (thighs, upper arms)
    • Distal (underarms) adds to the inclusion body myositite
  • Muscle strength
    • Raising from squatting without help?
    • Getting up from chair without support?
    • Handshake
    • Hard to raise the arms over the head?
    • The neck / head is hard to keep up?



Blood tests

*EMG (Electro-myography)

  • Myopathic changes at 90%
    • Increased activity and spontaneous fibrillation, abnormal myopathic amplitude, short polyphase motor potential, bizzare high frequency discharge
    • Separates from motor neuron disease, peripheral polymyopathy and myasthenia
    • Toxic, metabolic myopathy gives similar EMG as myositis

MRI (Magnetic Resonance Tomography) of the thigh muscles

  • Thigh muscles show inflammatory signs with edema, usually symmetrical. By fat suppression (T2) is seen (spotting edema), most along fascia. By inclusion body myositis, the entire muscle is infiltrated
  • Identifies area of ​​biopsy

X-ray Oesophagus (esophagus) with contrast agent

  • Swallowing function is examined with X-ray oesophagus (dynamic with swallowing contrast) or manometry (Gastromedical department)
  • Displays usually dysmotility
    • Oro-pharyngeal swelling muscle is affected, upper 1 / 3 part of esophagus
    • Risk of aspiration pneumonia

CT (Computer Resolution) / HRCT (High Resolution Computed Tomography) of lungs

  • Shows changes in lung tissue with "milk glass" (active inflammation) or fibrosis, honeycombing especially at Antisynthetase syndrome and eventually MDA-5 related (amyopathic) myositis
  • Basic infiltrates are typical
  • X-ray examination of the lungs is often normal, although widespread findings are made by CT examination

Kapillaroscopy (nail bed)

* Biopsy (tissue test)

  • Targeted muscle biopsy where MRI shows inflammation (most often musculus quadriceps or Deltoid).
  • Admission to bed post with one night after biopsy due to pain and bleeding risk
  • Agreement with pathology for in which medium the biopsy should be stored

* Histology (Result of tissue test)

  • Musculoskeletal Inflammation with mixed degeneration, regeneration and necrosis
  • Polymyositis
    • Inflammation is most in the muscle fibers: Endomyseal inflammation (accumulation of CD8 + T lymphocytes where some are observed inside non-dying cells). No vasculopathy or immune complex deposition.
  • Dermatomyositis
    • Perifascicular infiltrate or atrophy (capillary loss and ischemic injury). Reduced capillary density and membrane-attack-complex immune complex deposition are typical. Dermatomyositis resembles vasculitis with inflammatory processes mainly around peripheral vascular blood vessels (B lymphocytes and CD4 + T cells or plasmocytoid dendritic cells)
  • MHC1 upregulation At both PM and DM

Lung function tests

  • FEV1, FVC, DLCO (% of expected value)

Malignancy investigation by Dermatomyositis

Diagnosis of elevated serum creatinine kinase (CK)

  • Consider myositis and differential diagnoses
  • If CK is below 1000
    • The test is repeated without any prior physical activity
    • Trauma, physical overload, cramps, infections, injections, metabolic myopathy are among alternative causes
  • At very high CK (over 10.000) consider: Rhabdomyolysis
    • Troponin T (CTnT) is not specific to the heart muscle and often exceeds the skeletal muscle involvement. Troponin I (cTnI) is more myocardial specific.

Differential diagnoses of myositis, please read more here

Norwegian Directorate of Health (Supervisor for referrals)


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