A Japanese team evaluated the value of studying the motor plate in people who were negative for anti-RACh and anti-MuSK antibodies.
- Twenty people with symptoms suggestive of myasthenia had a neuromuscular biopsy of the biceps brachii.
- Five people had complement deposition in the motor plate :
. four of them also had a decrease in hACR density, comparable to that found in people with anti-hACR positive myasthenia,
. low-affinity RACh antibodies were found in two of them,
. all five were considered to have autoimmune myasthenia and were successfully treated as such. - The remaining fifteen people had other diagnoses during the ten years of follow-up, apart from one person who developed autoimmune myasthenia three years later.
The authors conclude that motor plate analysis is of diagnostic value in the absence of anti-RACh or anti-MuSK antibodies and, given the invasiveness of muscle biopsy, suggest that low-affinity anti-RACh antibodies should be sought first.
