Subgroup | Proportion of all myasthenia gravis (%) | Age of onset (years) | Sex (M:F) | Clinical features | AChR antibodies | MuSK antibodies | Thymus |
Ocular myasthenia gravis | 15–25 | 4–90 | 3:2 | Ptosis, ophthalmoplegia | Approx 50% | Very rare | Mild hyperplasia (30%) |
Early onset AChR-myasthenia gravis | 20–25 | 2–40 | 1:3 | Ptosis, ophthalmoplegia, generalised weakness | Approx 85% | Absent | Hyperplasia (>80%) |
Late onset AChR-myasthenia gravis | 30–40 | >40 | 3:2 | Ptosis, ophthalmoplegia, generalised weakness | Approx 60% | Absent | Atrophy |
MuSK-myasthenia gravis | 5–8 | 2–70 | 1:3 | Predominant ocular, facial and bulbar weakness | Absent | 100% | Normal or atrophy |
Seronegative myasthenia gravis | 5–10 | 10–70 | 1:2 | Ptosis, ophthalmoplegia, generalised weakness | Antibodies against clustered AChR in 50–60% | Absent | Mild hyperplasia |
AChR, acetylcholine receptor; MuSK, muscle specific tyrosine kinase.