Comparison of the histological and immunohistochemical features of the thymus in young- and elderly-onset myasthenia gravis without thymoma

Abstract

We performed histological and immunohistochemical analyses of the removed thymus in 20 elderly (onset age >60 years) and 23 young (onset age <40 years) patients with myasthenia gravis (MG) who showed positive anti-acetylcholine receptor (AChR) antibodies in serum without associated thymoma. In the elderly group nine (45%) demonstrated accumulations of lymphocytes indicating atrophied thymus without the basic structure. The elderly MG patients with atrophied thymic tissues showed higher titers of the anti-AChR antibody (59.6 81.0 nmol/l) than those with adipose tissue alone (20.1 20.9 nmol/l). In immunohistochemistry both the young group and elderly patients with atrophied thymic tissues showed significantly higher levels of CD20 on image analysis than the age-matched controls (p<0.005). Atrophied thymic tissues as often seen immunohistochemically in young MG patients might be found also in the elderly ones, particularly in those with high titers of the anti-AChR antibody, even though fat infiltration is remarkable.

Clinical and immunological features and treatment of myasthenia gravis in the elderly (review)

“…Так, W. Ishii и соавт. в 2005 г. при сравнении ткани тимуса пациентов с ранним и поздним началом миастении без тимомы не обнару-жили каких-либо значимых отличий [23]. К таким же выводам пришел J.…”

“…До сих пор нет общепринятого понимания, какой возраст манифестации миастении считать позд-ним. Ряд авторов определяют эту границу в возрасте 40-50 лет [8,[22][23][24][25], а другие -в возрасте 60 лет и старше [26,27].…”

Outcomes of Preoperative and Postoperative Corticosteroid Therapies in Myasthenia Gravis

“…Nikolic et al [28] investigated 138 thymectomized patients with GMG and found that complete stable or pharmacological remission were frequently observed in patients with a normal thymus (63.6%) and thymic lymphoid follicular hyperplasia (39.7%) and rarely observed in patients with thymoma (29.0%) and thymus atrophy (7.7%). In contrast, other studies have reported that thymus histopathology did not predict postoperative MG remission [22,26,27,29,30] . Chen et al [29] observed that B-cell activating factor receptor, CD19, and CD21 were not only increased in the hyperplasic thymus but also in the atrophic thymus, and patients with a hyperplasic thymus or atrophic thymus exhibited parallel postoperative prognoses.…”

“…Chen et al [29] observed that B-cell activating factor receptor, CD19, and CD21 were not only increased in the hyperplasic thymus but also in the atrophic thymus, and patients with a hyperplasic thymus or atrophic thymus exhibited parallel postoperative prognoses. Ishii et al [30] speculated that lymphocyte accumulation in the atrophic thymus indicates that residual thymus may also contribute to the immunopathogenesis of MG as a potential location for the induction of anti-AChR antibodies, despite hyperplasic thymus being considered the main source of AChR antibodies in AChR-MG pathophysiology.…”

Perioperative management in myasthenia gravis: republication of a systematic review and a proposal by the guideline committee of the Japanese Association for Chest Surgery 2014

“…The borderline between the early and late onset of MG is usually around 50 years old for the following reasons: (1) the sex ratio in MG patients reverses at this age; and (2) this age is just between the two peaks of early onset and late onset [29,30]. However, some researchers have described that the boundary should be at 40 years old based on the thymus pathology, while others have set it at 60 years old based on HLA and the autoantibody profile [31,32]. Patients with an onset at older than 65 years old are usually called elderly-onset MG.…”