The predictive value of the presence of different antibodies and thymus pathology to the clinical outcome in patients with generalized myasthenia gravis

Objectives

To analyze the predictive value of anti-acetylcholine receptor antibodies (anti-AChR Ab) and anti-muscle specific kinase antibodies (anti-MuSK Ab), as well as the thymus pathology to the clinical outcome in patients with generalized myasthenia gravis (MG).

Methods

We analyzed 138 patients with generalized MG, who were thymectomized and assayed for anti-AChR Ab and anti-MuSK Ab.

Results

Anti-AChR Ab were detected in 84% of patients, while anti-MuSK Ab were present in 36% of the AChR Ab negative patients. Severe forms of the disease were more frequent in MuSK Ab positive, compared to the AChR Ab positive and complete seronegative patients. Thymic lymphoid follicular hyperplasia (LFH) was present in 60%, thymoma in 23%, atrophic thymus in 9% and the normal thymus in 8% of patients. LFH was more frequent among women, while thymoma and atrophic thymus were more frequent in men. The younger patients mainly had LFH and normal thymus, while thymoma and atrophic thymus were more frequent in older patients. The mildest clinical presentation was present in patients with normal thymus, while severe forms of the disease were registered in the patients with thymoma. The AChR Ab positive patients had more often LFH and thymoma, while within MuSK Ab positive patients atrophic thymus was most common.

Conclusion

The best disease outcome was observed in patients with normal thymus or LFH with anti-AChR Ab or without both types of antibodies.