JUN 29, 2012
The authors of this article in the May 15 issue of Neurology retrospectively analyzed a multicenter cohort of patients with two rare organ-specific autoimmune diseases: aquaporin-4 antibody mediated (AQP4-Ab) neuromyelitis optica spectrum disorder (NMOSD) and acetylcholine receptor antibody mediated (AChr-Ab) myasthenia gravis (AChR-MG). They conclude that the association of MG and NMOSD occurs much more frequently than by chance.
The MG patients followed a benign course and, although most patients had MG and a thymectomy prior to the onset of NMOSD, it can occur first and in patients who have not undergone thymectomy. The authors suggest routine blood testing for thyroid disease and NMO in patients with early-onset MG.
The study included 16 patients identified from the databases of nine neurology centers worldwide. All of the patients had early-onset AChR-MG, the majority with mild generalized disease, and a high proportion achieved remission. Fifteen were female.
In 14 of the 16 patients, MG preceded NMOSD by a median of 16 years, and 11 of them had undergone a thymectomy, although one after NMOSD onset. In four of five patients tested, AQP4-Abs were detectable between four and 16 years prior to disease onset, including two patients with detectable AQP4-Abs prior to thymectomy.
AChR-Abs levels decreased and AQP4-Ab levels increased over time in concordance with the relevant disease. AChR-Abs were detectable at NMOSD onset in the one sample available from one of the two patients with NMOSD before MG.
The authors conclude that AChR-Abs or AQP4-Abs may be present years before onset of the relevant disease. They say that since clinical and laboratory features of the individual diseases and their time courses remain unchanged in patients with both conditions, this suggests coincident diseases. However, the relative increase in prevalence of patients with both AQP4-NMOSD and AChR-MG suggests these patients have a predisposition to autoimmunity, but the dynamics of the individual diseases remain unchanged.