Polymyositis and dermatomyositis laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sadaf Sharfaei M.D.[2]

Overview

Elevated sarcoplasmic enzymes are consistent with the diagnosis of polymyositis and dermatomyositis which include creatine phosphokinase, aldolase, transaminases, lactic dehydrogenase, and myoglobin. High white blood cell counts, low lymphocytes, and low hematocrit levels might be detected on CBC. Low albumin levels, high ESR and high IgM and IgG levels could be seen in patients with polymyositis and dermatomyositis. 20 myositis-specific autoantibodies are identified in patients with polymyositis and dermatomyositis. Anti-Jo-1 antibody is the most frequent myositis-specific autoantibodies which causes antisynthetase syndrome. Anti Mi-2 might be seen frequently in patients with dermatomyositis. Anti-SRP antibody is associated with very poor prognosis. Some of these myositis-specific autoantibodies are associated with malignancy. Anti-HMGCR antibody might be elevated in patients with statin-associated necrotizing autoimmune myopathy (SANAM).

Laboratory Findings

Different laboratory tests may be used to diagnose polymyositis and dermatomyositis and exclude other myopathies which include:^[1]^[2]^[3]^[4]^[5]^[6]^[7]^[8]
- Routine tests^[9]
- Sarcoplasmic enzymes
- Myositis-specific autoantibodies^[10]^[11]

Routine test

Abnormal test results include:
- CBC
  - High white blood cell counts
  - Low lymphocyte counts
  - Low hematocrit levels
- Low albumin levels
- High erythrocyte sedimentation rate
- High IgM and IgG levels

Sarcoplasmic enzymes

Sarcoplasmic enzymes consistent with the diagnosis of polymyositis and dermatomyositis include:^[12]
- Creatine phosphokinase including:
  - CK-MM
  - CK-MB
- Aldolase
- Transaminases
  - Alanine aminotransferase
  - Aspartate aminotransferase
- Lactic dehydrogenase
- Myoglobin

Myositis-specific autoantibodies

Autoantibody		Antigen	Features	Frequency
Antisynthetase	Anti-Jo-1	Histidyl-tRNA synthetase	Antisynthetase syndrome Arthritis Interstitial lung disease Fever Mechanic's hands Raynaud's phenomenon Flare up in spring Moderate response to treatment Poor prognosis Associated with epstein-Barr virus (EBV), adenovirus, and influenza infection	20-25%
	Anti-PL-7	Threonyl-tRNA synthetase	Myositis, mechanic's hands, Gottron's papules, arthritis	5-10%
	Anti PL-12	Alanyl-tRNA synthetase	Fever, Raynaud's phenomenon, high frequency of ILD Epstein-Barr virus (EBV), adenovirus, and influenza infection	<5%
	Anti PL-12	Alanyl-tRNA		<5%
	Anti-EJ	Glycyl-tRNA synthetase		5-10%
	Anti-OJ	Isoleucyl-tRNA synthetase		<5%
	Anti-KS	Asparaginyl-tRNA synthetase		<5%
	Anti-Ha	Tyrosyl-tRNA synthetase		<1%
	Anti-Zo	Phenylalanyl-tRNA synthetase		<1%
Others	Anti Mi-2	Chromodomain helicase DNA binding protein 4	Dermatomyositis rash without significant lung involvement Acute but mild onset Good prognosis	5-10%
	Anti-SRP	Signal recognition particle	Cardiac involvement Necrotizing myopathy Flare up in fall Very acute and severe onset Poor response to treatment Very poor prognosis	<5%
	Anti-p155/140	Transcriptional intermediary factor 1-gamma	Cancer-associated myositis Juvenile dermatomyositis Severe cutaneous disease	13-21% in IIM 23-29% in JDM
	Anti-MJ	Nuclear matrix protein (NXP-2)	Cancer-associated myositis Juvenile dermatomyositis	23% in JDM
	Anti-SAE	Small ubiquitin-like modifier activating enzyme	Cancer-associated myositis	5%
	Anti-caDM-140	Intracytoplasmic MDA5	Dermatomyositis and rapidly progressive ILD	50% (C-ADM)
	Anti-PMS1	DNA mismatch repair enzyme		7.5%
	Anti-HMGCR	3-hydroxy-3-methylglutaryl-coenzyme A reductase	Statin-associated necrotizing autoimmune myopathy (SANAM)	6%
	Anti-FER	Elongation factor 1 alpha
	Anti-KJ	Unidentified cytoplasmic protein
	Anti-MAS	Unidentified cytoplasmic RNA
	Anti–PM-Scl		Overlap of polymyositis and Scleroderma	25%

References

↑ Adler BL, Christopher-Stine L (February 2018). "Triggers of inflammatory myopathy: insights into pathogenesis". Discov Med. 25 (136): 75–83. PMID 29579414.
↑ Bodoki L, Nagy-Vincze M, Griger Z, Betteridge Z, Szöllősi L, Dankó K (December 2014). "Four dermatomyositis-specific autoantibodies-anti-TIF1γ, anti-NXP2, anti-SAE and anti-MDA5-in adult and juvenile patients with idiopathic inflammatory myopathies in a Hungarian cohort". Autoimmun Rev. 13 (12): 1211–9. doi:10.1016/j.autrev.2014.08.011. PMID 25182203.
↑ Khan, Sabiha; Christopher-Stine, Lisa (2011). "Polymyositis, Dermatomyositis, and Autoimmune Necrotizing Myopathy: Clinical Features". Rheumatic Disease Clinics of North America. 37 (2): 143–158. doi:10.1016/j.rdc.2011.01.001. ISSN 0889-857X.
↑ Dobloug, Cecilie; Garen, Torhild; Bitter, Helle; Stjärne, Johan; Stenseth, Guri; Grøvle, Lars; Sem, Marthe; Gran, Jan Tore; Molberg, Øyvind (2015). "Prevalence and clinical characteristics of adult polymyositis and dermatomyositis; data from a large and unselected Norwegian cohort". Annals of the Rheumatic Diseases. 74 (8): 1551–1556. doi:10.1136/annrheumdis-2013-205127. ISSN 0003-4967.
↑ Chinoy, H.; Fertig, N.; Oddis, C. V; Ollier, W. E R; Cooper, R. G (2007). "The diagnostic utility of myositis autoantibody testing for predicting the risk of cancer-associated myositis". Annals of the Rheumatic Diseases. 66 (10): 1345–1349. doi:10.1136/ard.2006.068502. ISSN 0003-4967.
↑ Dalakas, Marinos C; Hohlfeld, Reinhard (2003). "Polymyositis and dermatomyositis". The Lancet. 362 (9388): 971–982. doi:10.1016/S0140-6736(03)14368-1. ISSN 0140-6736.
↑ Douglas, William W.; Tazelaar, Henry D.; Hartman, Thomas E.; Hartman, Robert P.; Decker, Paul A.; Schroeder, Darrell R.; Ryu, Jay H. (2001). "Polymyositis–Dermatomyositis-associated Interstitial Lung Disease". American Journal of Respiratory and Critical Care Medicine. 164 (7): 1182–1185. doi:10.1164/ajrccm.164.7.2103110. ISSN 1073-449X.
↑ Miller, Frederick W. (1993). "Myositis-Specific Autoantibodies". JAMA. 270 (15): 1846. doi:10.1001/jama.1993.03510150080034. ISSN 0098-7484.
↑ Volochayev, Rita (2012). "Laboratory Test Abnormalities are Common in Polymyositis and Dermatomyositis and Differ Among Clinical and Demographic Groups". The Open Rheumatology Journal. 6 (1): 54–63. doi:10.2174/1874312901206010054. ISSN 1874-3129.
↑ Targoff, Ira N. (2006). "Myositis specific autoantibodies". Current Rheumatology Reports. 8 (3): 196–203. doi:10.1007/s11926-996-0025-3. ISSN 1523-3774.
↑ Gunawardena, H.; Betteridge, Z. E.; McHugh, N. J. (2009). "Myositis-specific autoantibodies: their clinical and pathogenic significance in disease expression". Rheumatology. 48 (6): 607–612. doi:10.1093/rheumatology/kep078. ISSN 1462-0324.
↑ Bohan, Anthony; Peter, James B. (1975). "Polymyositis and Dermatomyositis". New England Journal of Medicine. 292 (8): 403–407. doi:10.1056/NEJM197502202920807. ISSN 0028-4793.

[pmid29579414-1] Adler BL, Christopher-Stine L (February 2018). "Triggers of inflammatory myopathy: insights into pathogenesis". Discov Med. 25 (136): 75–83. PMID 29579414.

[pmid25182203-2] Bodoki L, Nagy-Vincze M, Griger Z, Betteridge Z, Szöllősi L, Dankó K (December 2014). "Four dermatomyositis-specific autoantibodies-anti-TIF1γ, anti-NXP2, anti-SAE and anti-MDA5-in adult and juvenile patients with idiopathic inflammatory myopathies in a Hungarian cohort". Autoimmun Rev. 13 (12): 1211–9. doi:10.1016/j.autrev.2014.08.011. PMID 25182203.

[KhanChristopher-Stine2011-3] Khan, Sabiha; Christopher-Stine, Lisa (2011). "Polymyositis, Dermatomyositis, and Autoimmune Necrotizing Myopathy: Clinical Features". Rheumatic Disease Clinics of North America. 37 (2): 143–158. doi:10.1016/j.rdc.2011.01.001. ISSN 0889-857X.

[DoblougGaren2015-4] Dobloug, Cecilie; Garen, Torhild; Bitter, Helle; Stjärne, Johan; Stenseth, Guri; Grøvle, Lars; Sem, Marthe; Gran, Jan Tore; Molberg, Øyvind (2015). "Prevalence and clinical characteristics of adult polymyositis and dermatomyositis; data from a large and unselected Norwegian cohort". Annals of the Rheumatic Diseases. 74 (8): 1551–1556. doi:10.1136/annrheumdis-2013-205127. ISSN 0003-4967.

[ChinoyFertig2007-5] Chinoy, H.; Fertig, N.; Oddis, C. V; Ollier, W. E R; Cooper, R. G (2007). "The diagnostic utility of myositis autoantibody testing for predicting the risk of cancer-associated myositis". Annals of the Rheumatic Diseases. 66 (10): 1345–1349. doi:10.1136/ard.2006.068502. ISSN 0003-4967.

[DalakasHohlfeld2003-6] Dalakas, Marinos C; Hohlfeld, Reinhard (2003). "Polymyositis and dermatomyositis". The Lancet. 362 (9388): 971–982. doi:10.1016/S0140-6736(03)14368-1. ISSN 0140-6736.

[DouglasTazelaar2001-7] Douglas, William W.; Tazelaar, Henry D.; Hartman, Thomas E.; Hartman, Robert P.; Decker, Paul A.; Schroeder, Darrell R.; Ryu, Jay H. (2001). "Polymyositis–Dermatomyositis-associated Interstitial Lung Disease". American Journal of Respiratory and Critical Care Medicine. 164 (7): 1182–1185. doi:10.1164/ajrccm.164.7.2103110. ISSN 1073-449X.

[Miller1993-8] Miller, Frederick W. (1993). "Myositis-Specific Autoantibodies". JAMA. 270 (15): 1846. doi:10.1001/jama.1993.03510150080034. ISSN 0098-7484.

[Volochayev2012-9] Volochayev, Rita (2012). "Laboratory Test Abnormalities are Common in Polymyositis and Dermatomyositis and Differ Among Clinical and Demographic Groups". The Open Rheumatology Journal. 6 (1): 54–63. doi:10.2174/1874312901206010054. ISSN 1874-3129.

[Targoff2006-10] Targoff, Ira N. (2006). "Myositis specific autoantibodies". Current Rheumatology Reports. 8 (3): 196–203. doi:10.1007/s11926-996-0025-3. ISSN 1523-3774.

[GunawardenaBetteridge2009-11] Gunawardena, H.; Betteridge, Z. E.; McHugh, N. J. (2009). "Myositis-specific autoantibodies: their clinical and pathogenic significance in disease expression". Rheumatology. 48 (6): 607–612. doi:10.1093/rheumatology/kep078. ISSN 1462-0324.

[BohanPeter1975-12] Bohan, Anthony; Peter, James B. (1975). "Polymyositis and Dermatomyositis". New England Journal of Medicine. 292 (8): 403–407. doi:10.1056/NEJM197502202920807. ISSN 0028-4793.

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