Sestre Milosrdnice University hospital and Institute of Clinical Medical Research
Abstract
Myasthenia gravis and Graves’ disease are two autoimmune diseases with a similar mechanism, both having circulating organ autoantibodies and cell specific autoantibodies. It is not unusual for these diseases to occur together. There is a large body of data proving that antithyroid drugs such as methimazole and propylthiouracil have an immunomodulatory effect in addition to their thyrosuppressant action. This case report describes a 34-year-old woman hospitalized for just diagnosed myasthenic crisis (Osserman IV). She had a prior history of hyperthyroidism and treatment with methimazole was initiated. However, improvement in thyroid disease led to the burst of myasthenia. The phenomenon described as worsening of one disease while improving the other, the so-called ‘see-saw’ relationship, occurred in this case. The question is whether antithyroid drugs improve hyperthyroidism while unveiling or worsening myasthenia. Is the ‘see-saw’ relationship actually a therapeutic side effect of antithyroid drug? The proposed mechanism of methimazole action is intracellular: it lowers the level of proliferating cell nuclear antigen (PCNA). PCNA pro¬motes selective apoptosis in some T lymphocyte clones. In this way, CD4+CD25+ regulatory T cells might ‘skip’ immune self-tolerance and autoantibodies against acetylcholine receptor may occur. Do antithyroid drugs actually create an immune ‘thymic surrounding’?Miastenija gravis i Gravesova bolest su dvije autoimune bolestI sa sličnim mehanizmom nastanka, u objema se nalaze cirkulirajuća antitijela te stanično specifična autoantitijela. Pojava navedenih bolesti zajedno nije neuobičajena. Postoji mnogo podataka koji pokazuju da antitireoidni lijekovi kao što su metimazol i propiltiouracil uz tireosupresivno djelovanje imaju i imunomodulacijski učinak. Opisuje se slučaj 34-godišnje bolesnice koja je hospitalizirana zbog prvi puta dijagnosticirane miastenije sa slikom miastenične krize (Osserman IV.). U njenoj ranijoj povijesti bolesti navodila se hipertireoza, zbog čega je započeto liječenje metimazolom. Međutim, uz poboljšanje bolesti štitnjače došlo je do pojave miastenije. Fenomen “klackalice”, tj. see-saw relationship, je pojava opisana kao poboljšanje jedne bolesti za vrijeme pogoršanja druge. Pitanje je poboljšavaju li antitireoidni lijekovi hipertireozu, u isto vrijeme razotkrivajući ili pogoršavajući miasteniju?. Jeli fenomen “klackalice” zapravo nuspojava tireostatika? Pretpostavljeni učinak metimazola je unutarstanični: on snižava razinu nuklearnog antigena stanične proliferacije (PCNA). PCNA potiče selektivnu apoptozu u nekim klonovima T limfocita. Na taj bi način CD4+CD25+ regulatorni T limfociti mogli ‘zaobići’ imunu toleranciju prema vlastitom tkivu te dovesti do pojave autoantitijela protiv acetilkolinskog receptora. Stvaraju li zapravo doista antitireoidni lijekovi okruženje slično onome u timusu
