Myasthenia gravis: an animated, cited guide

This page needs JavaScript for its animations. The outline and key answers are below, and every claim in the full version carries a numbered citation.

Not medical advice. Myasthenia Gravis Companion is an educational synthesis of published literature. It does not replace a clinician.

What is in it

What myasthenia gravis is Who gets it, the numbers, the muscles it reaches.
The neuromuscular junction One nerve impulse in slow motion, and the safety factor.
Antibodies at the junction AChR, complement, MuSK and LRP4, animated.
Weakness over a day Why muscles tire with use and recover with rest.
Diagnosis Antibodies, nerve tests, single-fibre EMG, a calculator.
MGFA class & scores MGFA classes I to V, MG-ADL and QMG, scored live.
The differential Lambert-Eaton, botulism, ALS, eye and muscle disease.
Pyridostigmine, animated Buying time at the receptor, dose by dose.
The treatment ladder From symptom relief to immunotherapy and biologics.
Thymectomy over the years The thymus, thymoma and the MGTX trial.
Complement & FcRn inhibitors The newer biologics, trial week by trial week.
Myasthenic crisis Triggers, the breathing numbers, ICU care.
Drugs that can worsen MG A cited checker: antibiotics, magnesium and more.
Nursing care Assessment, timing the doses, teaching, documentation.
Living with MG Pregnancy, surgery, exercise, vaccines, work.
Toward a cure CAR-T, B-cell targets and the evidence for each route.
History & people From Willis in 1672 to the biologics.
Flashcards, quiz and glossary Revision for students.
Sources Every reference behind the guide.

Part 1 · The disease

What myasthenia gravis is

Myasthenia gravis (MG) is an autoimmune disease of the nerve-muscle junction: muscles tire with use and recover with rest. Press play to watch weakness spread from the eyes to the breathing muscles while the age-of-onset charts fill in, then switch between ocular and generalized disease and the onset groups.

In MG, antibodies attack proteins on the muscle side of the neuromuscular junction: the acetylcholine receptor (AChR), muscle-specific kinase (MuSK) or related proteins. Weakness, local or general, is the main symptom. Patients are grouped by antibody, by which muscles are affected, by age at onset and by thymus pathology. ¹⁹⁸ The nerves and the muscles themselves are healthy, which is why sensation, reflexes and pupils stay normal. ^276,367

Distribution

Onset group

Timeline

The body map is schematic. Region percentages are first symptoms in a Japanese nationwide survey, 2015-2017. ⁵⁶⁷ The age curves are schematic shapes drawn from a published description (women: peaks near 30 and 50; men: rising, highest at 60-89), not measured values; the sex ratios printed on them are published. ¹⁰⁷ Filled bars and dots in the trend charts are published survey values. ^130,567

Which antibody? The subtypes

Most people with MG have antibodies against the acetylcholine receptor. A minority have MuSK antibodies, a few have LRP4 antibodies, and some have none that standard tests find. Thymoma is not an antibody type: it overlaps the AChR group. Tap a subtype.

Rounded to 100 people: AChR about 80% ^107,423, MuSK 7-10% ¹⁰⁷, and the remaining 12 squares double seronegative; published estimates for that group are 6-10% ⁵⁶⁴, so rounding makes it look a little larger here. LRP4 squares are derived (18.7% of the double-seronegative group ⁵⁷⁷), so they are drawn open. Estimates vary by country and assay.

How common? The estimates disagree

Pooled studies do not agree on how common MG is. Their prevalence estimates differ by more than twofold, mostly because of how a case is defined (insurance claims, laboratory results or clinical records) and when the studies were done. ^70,485,491 The chart shows each estimate with its own interval, not one blended number.

Filled dots are published point estimates; thick bars are 95% confidence intervals; thin lines are the range of the studies pooled; pale bars are ranges quoted by reviews. Per-100,000 figures are converted to per million. ^{70,107,327,345,473,485,491}

Course and prognosis, then and now

Older figures come from an era before immunotherapy and intensive care. Modern figures are lower, for conversion from eye-only to generalized disease and for deaths. The measures differ from study to study, so read each bar on its own.

All values are published. Each bar or dot is a different measure from a different study, so they are not one series. ^{16,64,100,107,235,276,304}

Other autoimmune disease and family

The clue: what stays normal

SensationNormal. Sensory nerves are not involved. ^128,367

ReflexesDeep tendon reflexes are normal. ³⁶⁷

PupilsNormal, even when the lids droop and the eyes cannot move together. ²⁷⁶

PainThe weakness is painless. ²⁷⁶

Exam hookFluctuating, fatigable weakness of eye, bulbar, limb or breathing muscles, with normal sensation, reflexes and pupils, points to the neuromuscular junction. Abnormal pupils point to a mimic such as botulism (dilated pupils in 37% of confirmed cases) ⁴⁴²; lost reflexes with a dry mouth point to Lambert-Eaton syndrome ^290,516. See The differential.

In plain wordsThe nerves and muscles are healthy. The message between them is weakened, so muscles tire quickly with use and recover with rest. Feeling, reflexes and the pupils are untouched.