Premium
Muscle histopathology in myasthenia gravis with antibodies against MuSK and AChR
Author(s) -
Martignago S.,
Fanin M.,
Albertini E.,
Pegoraro E.,
Angelini C.
Publication year - 2009
Publication title -
neuropathology and applied neurobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.538
H-Index - 95
eISSN - 1365-2990
pISSN - 0305-1846
DOI - 10.1111/j.1365-2990.2008.00965.x
Subject(s) - myasthenia gravis , atrophy , muscle biopsy , histopathology , medicine , antibody , acetylcholine receptor , muscle atrophy , endocrinology , biopsy , myofibril , autoantibody , pathological , pathology , biology , immunology , receptor
Aims: We compared myopathological features in myasthenia gravis (MG) patients with antibodies against AChR (seropositive) and muscle‐specific tyrosin‐kinase (MuSK). While the immunopathogenesis of seropositive MG is well known, there is a lack of pathological studies in anti‐MuSK antibody‐positive (MuSK+) MG. Methods: We analysed skeletal muscle biopsy features of 13 MG patients: 6 MuSK+ (all women) and 7 anti‐AchR antibody‐positive (AChR+) (2 women and 5 men). In our histopathological examination, we quantified the atrophy factor of both fibre types, and the extent of minicores, myofibrillar disarray, cytochrome c oxidase (COX)‐negative fibres, mitochondrial aggregates and fibre type grouping. Results: Mean muscle fibre atrophy factor was higher in AChR+ MG than MuSK+ MG, both in type I fibres (494 vs. 210) and particularly in type II fibres (1023 vs. 300). Fibre type grouping was observed in AChR+ MG whereas COX‐negative fibres were common in MuSK+ MG. Bulbar muscles were more severely affected in MuSK+ MG and the disease was more severe: the onset was usually earlier (39 years) with Myasthenia Gravis Foundation of America score III in MuSK+ MG, and score II was found in AChR+ MG (62 years). Conclusions: Muscle biopsies of MuSK+ MG show myopathic signs with prominent mitochondrial abnormalities, whereas neurogenic features and atrophy are more frequently found in AChR+ MG. The mitochondrial impairment could explain the oculo‐bulbar involvement in MuSK+ MG.