Contents
- 1 ICD-10 codes
- 2 The diagnosis is based on
- 3 Disease history / Symptoms
- 4 Investigations / Investigation
- 5 Blood tests
- 6 * EMG (electro-myography)
- 7 MR (magnetic resonance tomography) of the thigh muscles
- 8 X-ray Oesophagus (esophagus) with contrast agent
- 9 CT (Computer Resolution) / HRCT (High Resolution Computed Tomography) of lungs
- 10 Kapillaroscopy (nail bed)
- 11 * Biopsy (tissue test)
- 12 * Histology (Result of tissue test)
- 13 Lung function tests
- 14 Malignancy investigation by Dermatomyositis
- 15 Diagnosis of elevated serum creatinine kinase (CK)
- 16 Differential diagnosis of myositis, please read more here
- 17 Norwegian Directorate of Health (Supervisor for referrals)
ICD-10 codes
- Polymyositis M33.2
- Dermatomyositis M33.1
- Juvenil Dermatomyositis M33.0
- Antisynthetase syndrome M35.8 + J99.1
- Inclusion body myositis M60.8
- Myositis related to cancer M36.0
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:
Muscles
- * Symmetrical weakness in proximal muscle groups (classical)
- Often distal muscles at Inclusion body myositis
- Reduced strength
- Walking function affected (stairs, hills)
- Atrophy symmetrically, proximal / distal in muscles
- Swallowing Function:
- Hard to swallow? (Aspiration?)
- Signs of reduced heart muscle function? (myocarditis)
- Muscle pain (at 40%)
- * Elevated CK, maximum CK value (400-30.000?)
- Accompanying symptoms
- * Skin (rash: Dermatomyositis)
- Edema
- Subcutaneous swelling of high disease activity
- Dysphagia (esophagus infection)
- Hard to swallow solid food
- Aspiration
- Lungs (Antisynthetase syndrome)
- Dry cough
- Dyspnoea by strain
- Joints (Arthritis)
- Deformity in Tumors (90 - 90 Deformity)
- Flex in PIP joints (fingers) at Inclusion body myositis
- Possible triggering factors
- Drug Consumption (statins, drugs / heroin)
- Alcohol abuse
Immunosuppressive treatment
- Prednisolone, MTX, Mycophenolate (CellCept), Imurel, Ciclosporin, Tacrolimus, Rituximab, Cyclophosphamide, Immunoglobulin.
- Statins
Stimulants
- Tobacco (yes, not, previously)
- Alcohol
- Other drugs (Cocaine with more)
Investigations / Investigation
-
Clinical examination
Muscles
- 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?
Skin
- Erythroderma (Dermatomyositis)
- Subcutaneous edema (includes face), in high disease activity
- * Gottron's sign and papler
- Red-blue over MCP and PIP joints on extensor sides of elbows and knees) over MCP joints, elbows and knees. (Dermatomyositis)
- Mechanic's fingers
- Cracked fingertips (Antisynthetase syndrome)
- Arthritis (usually in fingers)
- * V-shaped eczema (neck / chest) (Dermatomyositis)
- * Shawl-shaped eczema (neck) (from the neck-shoulder blade) (Dermatomyositis)
- * Heliotropic rash (eyelids, most often children with dermatomyositis)
- Scleroderma (overlap of systemic sclerosis (Sklero myositis) or MCTD)
- Calcinosis (More often in children (Juvenile dermatomyositis)
- Raynaud's phenomenon (three-phasic, especially by antisyntetase syndrome)Lungs
- Cancer over lungs at auscultation
Heart
- Rhythm disturbances of the heart (myocarditis?)
- Heart failure (by myocarditis)
Blood tests
- Hgb, SR, CRP, leukocytes, platelets, liver enzymes, K, Na, Cl, Ca, Creatinine, TSH, f-T4, Creatine kinase (CK) troponin
- * Creative kinase (CK), LD and ASAT usually show high values
- Troponin T is often elevated
- There may be a manifestation of the heart muscle
- False elevated Troponin T values, however, are not rare.
- Troponin T can be increased by
- Myocardial Injury (heart attack, heart failure, cardiac contusion, cardiac amyloidosis, cardiac sarcoidosis
- Acute aortic dissection
- Acute respiratory distress syndrome (ARDS)
- Hypotension and shock
- Muscle trauma
- Pulmonary embolism
- Kidney failure
- Overtraining
- Subaracnoidal hemorrhage and stroke
- Inflammatory diseases
- (reference: Valfaie M, 2014)
- Troponin T can be increased by
- Troponin I is more heart muscle specific
- Antibodies are described on a separate page, please see here
- A selection:
- ANA, SSA / Ro (Signs Sjögren's syndrome or SLE?)
- Jo-1, PL12, PL7 (Antisynthetase Syndrome?)
- PMScl: Overlap of Systemic Sclerosis (scleroderma myositis)?
- RNP: MCTD?
- MDA-5 (Myocytis with severe lung infection)
- HMGCR (Statin-associated myositis)
- CCP (ACPA) Myositis at Rheumatoid arthritis
- Myositis-specific antibody (MSA, Immunological Laboratory OUS)
- A selection:
*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)
- Often pathological by dermatomyositis (vasculopathy)
- Bleeding, decreased capillary density, mega-capillaries, altered capillary architecture
- Please read more about capillary copy here
* 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
- If age over 40 years (or clinical suspicion)
- Gynecological examination, CT abdominal examination, electrophoresis urine / serum, hemofec, colonoscopy, possibly other us if clinical suspicion
- Alternatively: PET / CT examination
- Please read more about cancer and rheumatic disease here
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
- Short summary
- Nervous system disorders / Myopathy /ALS/MS (Paresthesia, pares, fasciculations, MR cerbrum)?
- Polymyalgia / Temporal arteritis?
- Pain Syndrome /Fibromyalgia?
- Parkinson's disease
Norwegian Directorate of Health (Supervisor for referrals)
Myositis, BINDEVEVSSYKDOMMER.no
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