False positive anti-acetylcholine receptor antibodies in motorneurone disease

The presence and clinical significance of autoantibodies in amyotrophic lateral sclerosis: a narrative review

Amyotrophic lateral sclerosis (ALS) is a debilitating and rapidly fatal neurodegenerative disease, which is characterized by the selective loss of the upper and lower motor neurons. The pathogenesis of ALS remains to be elucidated and has been connected to genetic, environmental and immune conditions. Evidence from clinical and experimental studies has suggested that the immune system played an important role in ALS pathophysiology. Autoantibodies are essential components of the immune system. Several autoantibodies directed at antigens associated with ALS pathogenesis have been identified in the serum and/or cerebrospinal fluid of ALS patients. The aim of this review is to summarize the presence and clinical significance of autoantibodies in ALS.

Diagnostic Challenge and Neuromuscular Junction Contribution to ALS Pathogenesis

Amyotrophic lateral sclerosis (ALS) represents the major adult-onset motor neuron disease. Both human and animal studies reveal the critical implication of muscle and neuromuscular junctions (NMJs) in the initial phase of this disease. Despite the common efforts, ALS diagnosis remains particularly challenging since many other disorders can overlap yielding similar clinical phenotypic features. A combination of further research on the NMJ parameters that are specific for this disease and laboratory tests are crucial for the early determination of specific changes in the muscle, as well as in motor neuron and the prediction of ALS progression. Also, it could provide a powerful tool in the discrimination of particular ALS and ALS-mimic cases and increase the efficacy of therapeutic treatments.

Amyotrophic Lateral Sclerosis and Myasthenia Gravis Overlap Syndrome: A Review of Two Cases and the Associated Literature

Objective

To describe the characteristics of patients with amyotrophic lateral sclerosis (ALS) and myasthenia gravis (MG) overlap syndrome and explore the relationship between the two diseases.

Methods

We conducted a search of medical records at Peking Union Medical University Hospital from 1983 to 2015 for coexistence of ALS and MG and searched the PubMed database for all literature describing ALS and MG overlap syndrome published through December 2016. We analyzed the clinical and neurophysiological characteristics of patients by groups according to strict diagnostic criteria.

Results

We presented 2 patients in our database with combined ALS and MG, and together with 25 cases reported in the literature, the patients were divided into 4 groups: 12 patients with MG followed by ALS, 8 patients with ALS followed by MG, 5 ALS patients with false-positive anti-acetylcholine receptor, and the other 2 ALS patients with only myasthenia symptoms. Most patients had limb onset ALS, and myasthenia symptoms mainly affected ocular and bulbar muscles. Clinical and neurophysiological characteristics were summarized.

Conclusion

These findings support the conclusion that immunological mechanisms and alterations in the neuromuscular junction are related to ALS pathogenesis.

Unusual association of amyotrophic lateral sclerosis and myasthenia gravis: A dysregulation of the adaptive immune system?

Myasthenia gravis is an autoimmune disorder affecting neuromuscular junctions that has been associated with a small increased risk of amyotrophic lateral sclerosis (ALS). Here, we describe a retrospective series of seven cases with a concomitant diagnosis of ALS and myasthenia gravis, collected among the 18 French reference centers for ALS in a twelve year period. After careful review, only six patients strictly met the diagnostic criteria for both ALS and myasthenia gravis. In these patients, limb onset of ALS was reported in five (83%) cases. Localization of myasthenia gravis initial symptoms was ocular in three (50%) cases, generalized in two (33%) and bulbar in one (17%). Median delay between onset of the two conditions was 19 months (6-319 months). Anti-acetylcholine receptor antibodies testing was positive in all cases. All patients were treated with riluzole and one had an associated immune-mediated disease. In the one last ALS case, the final diagnosis was false-positivity for anti-acetylcholine receptor antibodies. The co-occurrence of ALS and myasthenia gravis is rare and requires strict diagnostic criteria. Its demonstration needs thoughtful interpretation of electrophysiological results and exclusion of false positivity for myasthenia gravis antibody testing in some ALS cases. This association may be triggered by a dysfunction of adaptive immunity.

Double trouble: spinal muscular atrophy type II and seropositive myasthenia gravis in the same patient

Autosomal recessive proximal spinal muscular atrophy is caused by deletions in the survival of motor neuron (SMN1) gene, while autoimmune myasthenia gravis is an acquired disorder. An association between these two diseases has not been reported. Our patient with intermediate spinal muscular atrophy (SMA type II) did not need alimentary or respiratory aid until age 51 when he suddenly developed bulbar weakness and respiratory insufficiency. Seropositive myasthenia gravis was confirmed and the corresponding symptoms resolved on treatment.

Clinical implementation of anti-acetylcholine receptor antibodies

A multivariate analysis of anti-acetylcholine receptor (AChR) antibodies and clinical parameters other than treatment (modified Osserman groups, age, type of onset, sex, and thymus pathology) was performed for all incident (n = 366) myasthenia gravis (MG) cases in its white population in Denmark during the past 15 years. Sera from 244 healthy individuals and from 295 patients with diseases other than MG were analysed as controls. Formal statistics for the anti-AChR antibodies assay (immunoprecipitation RIA using crude human AChR extract) were calculated. The distribution of antibodies titres greater than 0.1 nMole/l was found to be approximately lognormal. For MG patients the 95% reference interval was 0.2-1549 nMoles/l, and in control sera the range was 0.0-0.4 nMole/l. Using 0.5 nMole/l as the cut-off level and regarding all results less than this value as normal titres, it appeared that the assay was highly specific (> 99.99%) for MG. In a population of MG patients significance should be attributed to values in the range 0.3-0.4 nMole/l. The overall diagnostic sensitivity was found to be 88%. The sensitivity appeared to be proportionate to clinical severity of MG. The percentage with a normal titre was higher (16%) for early onset of MG, compared with 7% for late onset. No significant difference in relation to the frequency of "negative titre" was found in relation to sex. Anti-AChR antibodies titre was found to correlate with clinical severity, female or male gender, and pathology of thymus. The groups of MG patients were not matched for the various clinical parameters but multiple regression analysis controlling for these variables revealed independent effects of clinical severity and sex though not of age. Normal thymus (including involuted gland) and thymoma were correlated with low to intermediate tires, and hyperplastic thymus with high level of antibodies. The clinical implementation of anti-AchR antibodies is reviewed from 1976 and up to the present. The problems with false positive results are thoroughly expounded.

Autoantibodies in D-penicillamine-induced myasthenia gravis: a comparison with idiopathic myasthenia and rheumatoid arthritis

The distribution of autoantibodies was studied in patients with rheumatoid arthritis (RA) treated by D-penicillamine and who developed myasthenia gravis (MG). The anti-human acetylcholine receptor (AChR) antibodies were specifically associated with clinical symptoms of MG without any difference in the pattern of specificities in idiopathic (id-MG) or in induced MG (DPen-MG). Conversely, anti-nuclear antibodies were elevated in DPen-MG sera compared to id-MG sera (P less than 0.001) but were also compared to patients with RA treated by D-penicillamine (or thiopronine) and who did not develop MG. Anti-denatured DNA antibodies were enhanced in sera from treated patients, whether they had presented or not a MG disease. Anti-histone antibodies were associated with RA. These observations suggest that the immunological imbalance in RA patients, can be increased by a drug treatment which may trigger the appearance of a second autoimmune disease such as MG, where anti-AChR antibodies are associated with anti-nuclear antibodies.