Background Hashimoto encephalopathy has been described as a syndrome of encephalopathy and high serum antithyroid antibody concentrations that is responsive to glucocorticoid therapy, but these could be chance associations. Objective To study a patient with Hashimoto encephalopathy and to review the literature to determine whether Hashimoto encephalopathy is an identifiable syndrome. Data Sources and Extraction We searched the MEDLINE database to June 2002 for "Hashimoto" or "autoimmune thyroiditis" and "encephalopathy" and examined all identified articles and articles referenced therein, including all languages. We included all patients with noninfectious encephalopathy (clouding of consciousness and impaired cognitive function) and high serum antithyroid antibody concentrations. We excluded patients if they did not meet these inclusion criteria or if their symptoms could be explained by another neurologic disorder. We recorded clinical features and the results of imaging, electroencephalographic, thyroid function, and cerebrospinal fluid studies. Data Synthesis We identified 85 patients (69 women and 16 men; mean age, 44 years) with encephalopathy and high serum antithyroid antibody concentrations. Among these patients, 23 (27%) had strokelike signs, 56 (66%) had seizures, 32 (38%) had psychosis, 66 (78%) had a high cerebrospinal fluid protein concentration, and 80 (98%) of 82 had abnormal electroencephalographic findings. Thyroid function varied from overt hypothyroidism to overt hyperthyroidism; the most common abnormality was subclinical hypothyroidism (30 patients [35%]). Among patients treated with glucocorticoids, 66 (96%) improved. Conclusions The combination of encephalopathy, high serum antithyroid antibody concentrations, and responsiveness to glucocorticoid therapy seems unlikely to be due to chance. However, there is no evidence of a pathogenic role for the antibodies, which are probably markers of some other autoimmune disorder affecting the brain.

https://jamanetwork.com/journals/jamaneurology/articlepdf/783630/NNR20012.pdf

Hashimoto encephalopathy: syndrome or myth?

http://dosequis.colorado.edu/Courses/BrainWeb/papers/MG1.pdf

Myasthenia gravis: a comprehensive review of immune dysregulation and etiological mechanisms.

Objective: To describe 16 patients with a coincidence of 2 rare diseases: aquaporin-4 antibody (AQP4-Ab)–mediated neuromyelitis optica spectrum disorder (AQP4-NMOSD) and acetylcholine receptor antibody (AChR-Ab)–mediated myasthenia gravis (AChR-MG). Methods: The clinical details and antibody results of 16 patients with AChR-MG and AQP4-NMOSD were analyzed retrospectively. Results: All had early-onset AChR-MG, the majority with mild generalized disease, and a high proportion achieved remission. Fifteen were female; 11 were Caucasian. In 14/16, the MG preceded NMOSD (median interval: 16 years) and 11 of these had had a thymectomy although 1 only after NMOSD onset. In 4/5 patients tested, AQP4-Abs were detectable between 4 and 16 years prior to disease onset, including 2 patients with detectable AQP4-Abs prior to thymectomy. AChR-Abs decreased and the 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 1 of the 2 patients with NMOSD before MG. Conclusions: Although both conditions are rare, the association of MG and NMOSD occurs much more frequently than by chance and the MG appears to follow a benign course. AChR-Abs or AQP4-Abs may be present years before onset of the relevant disease and the antibody titers against AQP4 and AChR tend to change in opposite directions. Although most cases had MG prior to NMOSD onset, and had undergone thymectomy, NMOSD can occur first and in patients who have not had their thymus removed.

Myasthenia gravis and neuromyelitis optica spectrum disorder: a multicenter study of 16 patients.

We conducted a study of the epidemiology of myasthenia gravis (MG) in four locations in central and western Virginia from 1970 through 1984. The population surveyed was 555,851 in 1984. A total of 73 new cases of MG occurred during the survey period, producing an overall average annual incidence rate of 9.1 per million. The point prevalence rate in 1980 was 13.4 per 100,000, and in 1984 it was 14.2. Approximately 15% of the population was black, and we found that incidence and prevalence rates for the black population were higher than the corresponding white population. When the population was subdivided into <50 and 50+ age groups, the incidence and prevalence were significantly higher in the older group. The rates we report here are higher than rates reported from any other locality. The reasons for the higher rates include optimal case identification, survey of a population with a higher incidence, and increasing aging of the population.

The epidemiology of myasthenia gravis in central and western Virginia.

Autoimmune thyroid disease (AITD) is common and occurs frequently in conjunction with other diseases. Many putative disease associations have been suggested for AITD but the validity of these associations is not clear in all cases. It is important to define disease associations correctly because this may offer a means to rationally screen for true associations, may shed light on shared pathophysiologic mechanisms and may be important if the associated disease impacts on patient management. This review has examined the evidence base for a large number of the suggested associations.

Disease Associations with Autoimmune Thyroid Disease

The prevalence of myasthenia gravis (MG) in the counties of Hordaland and Sogn & Fjordane on January 1, 1984 was 9.6 per 100,000 inhabitants. Other autoimmune diseases were found in 11 out of 48 MG patients. The occurrence of autoimmune thyroiditis (5 patients, 10.4%) and systemic lupus erythematosus (4 patients, 8.3%) in the MG patients was clearly higher than that reported in the general population. Rheumatoid arthritis was found in 2 patients (4.2%). The autoimmune diseases were mainly recorded among the nonthymectomized MG patients. In addition to those with definite diseases of autoimmune nature, 3 other MG patients had thyroid antibodies and 1 had antinuclear factor without clinical evidence of autoimmune disease. Seven MG patients (14.6%) had unspecific arthralgia during active periods of MG. Two MG patients had ankylosing spondylitis.

T. Riise

Papers

Associated disorders in myasthenia gravis: autoimmune diseases and their relation to thymectomy.