Myasthenia gravis
An autoimmune condition in which antibodies disrupt the signal between nerves and muscles, causing muscle weakness that gets worse with use and better with rest. It typically affects the eyes, face, throat and limbs, and is confirmed largely by an antibody blood test.
What it is
Myasthenia gravis is an autoimmune disorder of the connection between nerve and muscle. Antibodies — most often against the acetylcholine receptor — block or destroy the receptors that receive the nerve's 'contract' signal, so muscles fail to respond properly. The defining feature is fatigable weakness: muscles work at first but tire quickly with repeated use and recover with rest, so weakness typically worsens through the day. It often starts in the eyes, causing drooping eyelids and double vision, and may spread to the face, throat and limbs, affecting speech, chewing, swallowing, and arm or leg strength. In some people it stays confined to the eyes (ocular myasthenia); in others it is generalised. A dangerous complication is a myasthenic crisis, in which weakness of the breathing muscles becomes severe and life-threatening. Diagnosis rests on the clinical pattern plus the acetylcholine receptor antibody blood test (positive in most people; others carry MuSK antibodies or are seronegative), sometimes with nerve-muscle electrical studies, and imaging of the thymus gland, which is often abnormal. It is linked to other autoimmune conditions, especially thyroid disease. Treatments — drugs that boost the nerve signal, immune-suppressing therapy, and sometimes thymus removal — control it well in most people.
Key lab markers
- Acetylcholine receptor antibody — the hallmark test; positive in most people with generalised disease.
- MuSK antibody — tested when the AChR antibody is negative but the picture fits.
- TSH and thyroid antibodies — autoimmune thyroid disease commonly coexists and is screened for.
- Creatine kinase — usually normal, helping distinguish it from primary muscle diseases.
- Thymus imaging (CT) — not a blood test, but part of the work-up for thymoma.
Symptoms
- Drooping eyelids and double vision (often the first sign)
- Weakness that worsens with use and improves with rest
- Weakness typically worse later in the day
- Slurred or nasal speech, and difficulty chewing or swallowing
- Weakness of the arms, legs or neck
- In severe cases, difficulty breathing (a medical emergency)
Related lab panels
When to discuss with a doctor
See a doctor about muscle weakness that fluctuates and fatigues with use — particularly drooping eyelids, double vision, or difficulty with speech, chewing or swallowing that worsens through the day. These warrant neurological assessment and an acetylcholine receptor antibody blood test, which strongly supports the diagnosis when positive. Crucially, weakness that affects breathing or swallowing can become a life-threatening myasthenic crisis and needs urgent emergency care — do not wait. Because thyroid and other autoimmune conditions often coexist, these are checked too. With treatment, most people do well. Mediora.AI shows the acetylcholine receptor antibody and related tests together so the picture is clear, but the diagnosis and treatment of myasthenia gravis belong with a neurologist, and any breathing or swallowing difficulty is an emergency.