Acta Neuropathologica: Serum-negative severe muscle weakness patient neuromuscular joint complement deposition.

The involvement of the tonic system in the onset of severe muscle weakness (MG) depends on the IgG sub-type.
serum antiacetylene receptamination antibodies (AChR-ab, present in about 80% of MG patients) are essentially IgG1 subtypes and therefore activate the classic complement pathway.
contrast, serum antibodies against muscle-specific tyrosine kinase (MuSK-ab, present in 3% of patients with severe muscle weakness) mostly come from IgG4 subtypes that do not activate the complement system.
15% of MG patients are called 'serum negative', meaning no known serum antibodies can be detected.
The diagnosis of clinical symptoms alone risks underdiagnosis, which may exclude SNMG patients from modern treatment, but targeted complement inhibition (eculizumab) has recently been introduced to treat AChR-ab-positive, standard non-reactive systemic MG patients.
the purpose of this study is to determine a reliable biomarker to justify the complementary target therapy SNMG.
: In order to study the role of complement system in SNMG, a cross-sectional study was carried out on 11 patients with incurable SNMG disease, who underwent a prospective rib biopsy.
, the authors also reviewed two patients with SNMG disease previously conducted triangular muscle biopsies.
the average age of the 13 patients was 44.0 years (standard deviation 19.8), of which 9 were women.
duration of the disease was 6.3 years (standard deviation was 5.3).
severity of the disease ranged from MGFA IIa-V, and eight patients had a history of muscle weakness.
diagnosis of SNMG disease was determined as follows: (1) typical clinical manifestations of fatigue muscle weakness improved with rest; (through indirect immunofluorescence testing, IIFT) to detect autoantibodies, (3) repeated abnormal results of neurostimulation and/or monofibre electromyograms, and/or (4) clinical responses to intravenous or oral acetylcholinesterase inhibitors.
conclusion: The evidence of histological pathology involving SNMG complement system may have diagnostic and therapeutic correlations.
biopsy and histological pathology analysis of external rib muscles appears to be a feasible diagnostic step in establishing SNMG diagnosis, especially in the course of incurable diseases.
Hoffmann, S., Harms, L., Schuelke, M. et al. Complete deposition at the neuromuscularular in seronegative myasthenia gravis. Acta Neuropathol 139, 1119-1122 (2020). Source: MedSci Original !-- Content Show Ends - !-- Determines whether login Ends.