The simplest subdivision of myasthenia gravis is as follows:
- Ocular myasthenia – only the external eye muscles are affected.
- Generalized myasthenia – involvement of facial, pharyngeal, cervical/neck, and skeletal muscles; mild/medium/severe expression possible
- Paraneoplastic myasthenia – in case of thymoma (tumor originating from thymic tissue).
- Congenital (congenital) myasthenia (rare) – autosomal recessive inherited disorder, with onset in childhood; not immune-mediated; pre- and postsynaptic (located before and after the synapse) abnormalities.
Neonatal myasthenia is a special form. In this case, IgG class autoantibodies cross the placental barrier and cause transient (temporary) neonatal myasthenia. The manifestations of the neonatal variant of the disease develop in the first days after birth. The incidence is approximately 1 in 12 newborns born to mothers with myasthenia. Autoantibodies can also be transmitted via the colostrum (colostrum) in the first days after birth. However, there is no objection to breastfeeding, as the symptoms usually subside after a few weeks. After more than three months, the acetylcholine receptor antibodies are no longer detectable. Myasthenia is not expected to occur in the child later in life. A classification of myasthenia gravis was designed by Ossermann in 1958 and modified by the American society MGFA. Here it comes to a categorization of patients with the same clinical characteristics into corresponding cohorts. Clinical classification of myasthenia gravis (modified MGFA classification 2000) [according to guideline]:
| Class | Characteristics |
| I | Pure ocular myasthenia limited to external eye muscles and eyelid closure |
| II | Mild to moderate generalized myasthenia involving other muscle groups, often including eye muscles |
| III | Moderate-grade generalized myasthenia, often including eye muscles |
| IV | Severe generalized myasthenia |
| V | Need for intubation with and without ventilation* . |
| Classes II to IV can be divided into 2 subgroups: | |
| A | Emphasis on extremities and/or limb girdles, minor involvement of oropharyngeal (affecting the mouth and throat) muscle groups |
| B | Specific involvement of oropharyngeal and/or respiratory muscles, lesser or equal involvement of extremities or trunk-related muscle groups |
| * Need for nasal tube without need for intubation: class IVb. | |
The different forms and manifestations of myasthenia gravis are shown in the table below. Clinicopathogenetic classification of MG (modified and expanded from Compston, Vincent) [as per guideline]:
| Early-Onset Myasthenia gravis (EOMG). | Late-Onset Myasthenia gravis (LOMG). | Thymoma-associated MG (TAMG). | Anti-MuSK AK-associated MG (MAMG). | Ocular MG (OMG) | |
| Estimated frequency | 20 % | 45 % | 10-15 % | 6 % | 15 % |
| Course and manifestation |
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| Age at start |
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| Men: Women | 1: 3 | 5: 1 | 1: 1 | 1: 3 | 1: 2 |
| HLA association (Caucasian) |
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not specified |
| (Auto)antibody |
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| Typical thymus pathology |
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| Response to thymectomy (removal of the thymus/bris). |
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| Response to immunotherapy | +++ | +++ | +(+) | +(+) | +++ |
