Myasthenia gravis laboratory findings

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Laboratory findings consistent with the diagnosis of myasthenia gravis include: Acetylcholine receptor antibodies, muSK antibodies, anti-striated muscle antibodies, antibodies to titin and other antibodies such as: antibody against LRP4 (which are IgG1)[1], cortactin (which help AChR clustering)[2], ryanodine receptor, myosin, alpha actin, rapsyn and gravin.

Laboratory Findings

Laboratory findings consistent with the diagnosis of myasthenia gravis include:

Acetylcholine receptor antibodies:

  • One of the most important steps in confirming the diagnosis of myasthenia gravis is detecting AchR-Ab.
  • About 85 percent of patients with generalized myasthenia gravis are seropositive for this Abs.[3][4]
  • These antybodies are specific for myasthenia gravis but in rare cases we have false positive such as lambert-eaton, motor neuron disease, polymyositis[5][6] and even in the disease not related to myasthenia such as primary biliary cholangitis and systemic lupus erythematosus.[7][8]
  • Since the patient can become seronegative after immune modulating therapy, this test should be done before treatment.[9]

MuSK antibodies:

  • About 38 to 50 percent of patients with generalized disease, who are seronagative for AChR-Ab, have antibodies against muscle specific receptor tyrosine kinase (MuSK).[9] [10][11][12][13]
  • These antibodies are not commonly seen in patients with well-established ocular myasthenia gravis.[14][15]
  • This test can be useful in patients who have the typical presentation of myasthenia gravis but are negative for AChR-Ab.[11]

Anti-striated muscle antibodies:

  • These antibodies are present in about 80 percent of patients with thymoma and in 36 percent of myasthenia gravis patients overlay.[3]
  • In patients with early onset myasthenia (20 to 50 years old) these antibodies are useful in detecting thymomas.[4]

Antibodies to titin:

  • Antibody to this protein which is an intracellular muscle protein is seen in about 95 percent of patients with myasthenia gravis and thymoma and in 50 percent of patients with myasthenia without thymoma.[16]

Other antibodies:


  1. 1.0 1.1 Higuchi O, Hamuro J, Motomura M, Yamanashi Y (February 2011). "Autoantibodies to low-density lipoprotein receptor-related protein 4 in myasthenia gravis". Ann. Neurol. 69 (2): 418–22. doi:10.1002/ana.22312. PMID 21387385.
  2. 2.0 2.1 Madhavan R, Gong ZL, Ma JJ, Chan AW, Peng HB (December 2009). "The function of cortactin in the clustering of acetylcholine receptors at the vertebrate neuromuscular junction". PLoS ONE. 4 (12): e8478. doi:10.1371/journal.pone.0008478. PMC 2793544. PMID 20041195.
  3. 3.0 3.1 Vernino S, Lennon VA (November 2004). "Autoantibody profiles and neurological correlations of thymoma". Clin. Cancer Res. 10 (21): 7270–5. doi:10.1158/1078-0432.CCR-04-0735. PMID 15534101.
  4. 4.0 4.1 Choi Decroos E, Hobson-Webb LD, Juel VC, Massey JM, Sanders DB (January 2014). "Do acetylcholine receptor and striated muscle antibodies predict the presence of thymoma in patients with myasthenia gravis?". Muscle Nerve. 49 (1): 30–4. doi:10.1002/mus.23882. PMID 23625360.
  5. Howard FM, Lennon VA, Finley J, Matsumoto J, Elveback LR (1987). "Clinical correlations of antibodies that bind, block, or modulate human acetylcholine receptors in myasthenia gravis". Ann. N. Y. Acad. Sci. 505: 526–38. PMID 3479935.
  6. Mittag TW, Caroscio J (April 1980). "False-positive immunoassay for acetylcholine-receptor antibody in amyotrophic lateral sclerosis". N. Engl. J. Med. 302 (15): 868. doi:10.1056/NEJM198004103021520. PMID 7360170.
  7. Sundewall AC, Lefvert AK, Olsson R (1985). "Anti-acetylcholine receptor antibodies in primary biliary cirrhosis". Acta Med Scand. 217 (5): 519–25. PMID 4025008.
  8. Pascuzzi RM, Phillips LH, Johns TR, Lennon VA (1987). "The prevalence of electrophysiological and immunological abnormalities in asymptomatic relatives of patients with myasthenia gravis". Ann. N. Y. Acad. Sci. 505: 407–15. PMID 3479932.
  9. 9.0 9.1 Chan KH, Lachance DH, Harper CM, Lennon VA (November 2007). "Frequency of seronegativity in adult-acquired generalized myasthenia gravis". Muscle Nerve. 36 (5): 651–8. doi:10.1002/mus.20854. PMID 17654558.
  10. McConville J, Farrugia ME, Beeson D, Kishore U, Metcalfe R, Newsom-Davis J, Vincent A (April 2004). "Detection and characterization of MuSK antibodies in seronegative myasthenia gravis". Ann. Neurol. 55 (4): 580–4. doi:10.1002/ana.20061. PMID 15048899.
  11. 11.0 11.1 Sanders DB, El-Salem K, Massey JM, McConville J, Vincent A (June 2003). "Clinical aspects of MuSK antibody positive seronegative MG". Neurology. 60 (12): 1978–80. PMID 12821744.
  12. Vincent A, McConville J, Farrugia ME, Newsom-Davis J (March 2004). "Seronegative myasthenia gravis". Semin Neurol. 24 (1): 125–33. doi:10.1055/s-2004-829589. PMID 15229799.
  13. Lavrnic D, Losen M, Vujic A, De Baets M, Hajdukovic LJ, Stojanovic V, Trikic R, Djukic P, Apostolski S (August 2005). "The features of myasthenia gravis with autoantibodies to MuSK". J. Neurol. Neurosurg. Psychiatry. 76 (8): 1099–102. doi:10.1136/jnnp.2004.052415. PMC 1739764. PMID 16024887.
  14. Caress JB, Hunt CH, Batish SD (June 2005). "Anti-MuSK myasthenia gravis presenting with purely ocular findings". Arch. Neurol. 62 (6): 1002–3. doi:10.1001/archneur.62.6.1002. PMID 15956173.
  15. Hanisch F, Eger K, Zierz S (May 2006). "MuSK-antibody positive pure ocular myasthenia gravis". J. Neurol. 253 (5): 659–60. doi:10.1007/s00415-005-0032-8. PMID 16311895.
  16. Romi F, Skeie GO, Gilhus NE, Aarli JA (March 2005). "Striational antibodies in myasthenia gravis: reactivity and possible clinical significance". Arch. Neurol. 62 (3): 442–6. doi:10.1001/archneur.62.3.442. PMID 15767509.
  17. Ohta M, Ohta K, Itoh N, Kurobe M, Hayashi K, Nishitani H (March 1990). "Anti-skeletal muscle antibodies in the sera from myasthenic patients with thymoma: identification of anti-myosin, actomyosin, actin, and alpha-actinin antibodies by a solid-phase radioimmunoassay and a western blotting analysis". Clin. Chim. Acta. 187 (3): 255–64. PMID 2323065.
  18. Nauert JB, Klauck TM, Langeberg LK, Scott JD (January 1997). "Gravin, an autoantigen recognized by serum from myasthenia gravis patients, is a kinase scaffold protein". Curr. Biol. 7 (1): 52–62. PMID 9000000.
  19. Agius MA, Zhu S, Kirvan CA, Schafer AL, Lin MY, Fairclough RH, Oger JJ, Aziz T, Aarli JA (May 1998). "Rapsyn antibodies in myasthenia gravis". Ann. N. Y. Acad. Sci. 841: 516–21. PMID 9668284.

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