Myasthenia gravis laboratory findings: Difference between revisions
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==== Antibodies to titin: ==== | ==== 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.(45) | 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.(45) | ||
==== Other antibodies: ==== | |||
some patients may be positive for other [[antibodies]] including [[antibody]] against LRP4 (which are IgG1)<ref name="pmid21387385">{{cite journal |vauthors=Higuchi O, Hamuro J, Motomura M, Yamanashi Y |title=Autoantibodies to low-density lipoprotein receptor-related protein 4 in myasthenia gravis |journal=Ann. Neurol. |volume=69 |issue=2 |pages=418–22 |date=February 2011 |pmid=21387385 |doi=10.1002/ana.22312 |url=}}</ref>, [[cortactin]] (which help [[Acetylcholine receptor|AChR]] clustering)<ref name="pmid20041195">{{cite journal |vauthors=Madhavan R, Gong ZL, Ma JJ, Chan AW, Peng HB |title=The function of cortactin in the clustering of acetylcholine receptors at the vertebrate neuromuscular junction |journal=PLoS ONE |volume=4 |issue=12 |pages=e8478 |date=December 2009 |pmid=20041195 |pmc=2793544 |doi=10.1371/journal.pone.0008478 |url=}}</ref>, [[ryanodine receptor]], [[myosin]], alpha actin, rapsyn and gravin.<ref name="pmid2323065">{{cite journal |vauthors=Ohta M, Ohta K, Itoh N, Kurobe M, Hayashi K, Nishitani H |title=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 |journal=Clin. Chim. Acta |volume=187 |issue=3 |pages=255–64 |date=March 1990 |pmid=2323065 |doi= |url=}}</ref><ref name="pmid9000000">{{cite journal |vauthors=Nauert JB, Klauck TM, Langeberg LK, Scott JD |title=Gravin, an autoantigen recognized by serum from myasthenia gravis patients, is a kinase scaffold protein |journal=Curr. Biol. |volume=7 |issue=1 |pages=52–62 |date=January 1997 |pmid=9000000 |doi= |url=}}</ref><ref name="pmid9668284">{{cite journal |vauthors=Agius MA, Zhu S, Kirvan CA, Schafer AL, Lin MY, Fairclough RH, Oger JJ, Aziz T, Aarli JA |title=Rapsyn antibodies in myasthenia gravis |journal=Ann. N. Y. Acad. Sci. |volume=841 |issue= |pages=516–21 |date=May 1998 |pmid=9668284 |doi= |url=}}</ref> | |||
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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.(8-9) these antybodies are specific for myasthenia gravis but in rare cases we have false positive such as lambert-eaton, motor neuron disease, polymyositis(10-15-16) and even in the disease not related to myasthenia such as primary biliary cholangitis and systemic lupus erythematosus.(17-18) since the patient can become seronegative after immune modulating therapy, this test should be done before treatment. (12)
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) (12-20 ta 26) these antibodies are not commonly seen in patients with well-established ocular myasthenia gravis. (28-29) This test can be useful in patients who have the typical presentation of myasthenia gravis but are negative for AChR-Ab.(21)
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.(9) in patients with early onset myasthenia (20 to 50 years old) these antibodies are useful in detecting thymomas.(9,42)
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.(45)
Other antibodies:
some patients may be positive for other antibodies including antibody against LRP4 (which are IgG1)[1], cortactin (which help AChR clustering)[2], ryanodine receptor, myosin, alpha actin, rapsyn and gravin.[3][4][5]
References
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.