Your next patient has had double vision and a droopy eyelid for 3 months, now weak and choking on drinks. Here's how the myasthenia gravis case unfolds and what to pick up on the way.

It’s easy to miss a myasthenia gravis case in clinic because ‘worse when tired’ sounds like ordinary fatigue, and the weakness fluctuates with use and rest. Your next patient has had double vision and a droopy eyelid for 3 months, is now weak and choking on drinks, and says: ‘A few months of double vision and a drooping eyelid, and now feeling weak.’

This page walks through how the case presents, what to pick up in the history, the tests and the teaching points: the classic pattern of ocular signs that worsen with sustained use, bulbar symptoms such as nasal or slurred speech and choking on fluids, proximal limb fatiguability with normal sensation and preserved reflexes, and why these stories are often dismissed as stress or feeling run down.

How the case presents

Your next patient has had double vision and a droopy eyelid for 3 months, now weak and choking on drinks. In their own words: "A few months of double vision and a drooping eyelid, and now feeling weak."

Observations on arrival:

Observation	On arrival
Heart rate	104 beats per minute
Blood pressure	132/80 mmHg
Respiratory rate	24 breaths per minute
Oxygen saturation	97%
Temperature	37 °C

What to pick up in the history

These are the findings the case is built around. Each one moves you towards or away from myasthenia gravis, and the scorecard checks whether you found it.

Weakness best on waking, worse through the day: fatiguability improving with rest is the defining feature and separates myasthenia from ordinary tiredness or depression.
Double vision and drooping lid after sustained use: fluctuating ptosis and diplopia that recover with rest are the classic ocular onset of myasthenia gravis.
Speech goes slurred and nasal; chokes on fluids: bulbar involvement means an unsafe swallow and marks a high-risk patient needing admission and airway vigilance.
Breathless lying flat, sleeping propped up: orthopnoea signals diaphragmatic weakness and impending myasthenic crisis; track serial FVC, not oxygen saturation.
Arms tire and drop after sustained use: proximal fatiguable limb weakness shows the disease has generalised beyond purely ocular myasthenia.
Sensation entirely normal, no numbness or pain: normal sensation makes this a pure motor disorder, excluding neuropathy and arguing against Guillain-Barre.
Reflexes normal and preserved: preserved reflexes separate myasthenia from the areflexia of Guillain-Barre and from Lambert-Eaton syndrome.

Red flags you must not miss

The case marks these as must-elicit. They only come out if you ask.

Weakness best on waking, worse through the day.
Double vision and drooping lid after sustained use.
Speech goes slurred and nasal; chokes on fluids.
Breathless lying flat, sleeping propped up.
Arms tire and drop after sustained use.
Sensation entirely normal, no numbness or pain.

Investigations and what they showed

Thyroid function tests: Screened because autoimmune thyroid disease commonly coexists with myasthenia gravis. Why it helps: myasthenia is associated with other autoimmune conditions (especially thyroid disease), and thyroid dysfunction can worsen weakness.
Full blood count: Shows the recent chest infection; otherwise unremarkable.
C-reactive protein: Raised from the recent chest infection.
Arterial blood gas: May show a rising CO2 (type 2 respiratory failure), a late and ominous sign; oxygenation is preserved until very late.
Anti-acetylcholine receptor antibody: Acetylcholine receptor (AChR) binding antibodies positive (raised); anti-MuSK antibodies negative, confirms generalised myasthenia gravis, in keeping with the thymoma. Why it helps: anti-MuSK is only worth sending if AChR is negative.
Spirometry: Forced vital capacity is reduced and falling on serial measurement, the single most important monitoring test, indicating impending myasthenic crisis. Why it helps: the critical bedside test.
Nerve conduction studies: Repetitive nerve stimulation shows a decremental response, progressively falling cmap amplitudes on successive stimuli (single-fibre EMG is more sensitive still). Why it helps: neurophysiology confirms the neuromuscular junction defect and distinguishes it from neuropathy and myopathy.
CT chest: An anterior mediastinal mass, a thymoma.
X-ray chest: May show the mediastinal mass and identifies the recent chest infection/aspiration. Why it helps: screens for the infective precipitant and for aspiration from bulbar weakness.
Inspect the eyelids: Asymmetrical drooping of the upper eyelids, one lid hangs low enough to cover the top of the pupil while the other is almost fully open. The brow on the drooping side is lifted by overworked frontalis. Ask him to hold a sustained upward gaze for 60 seconds and the lid creeps progressively further down (fatiguable ptosis). Why it helps: fatiguable, asymmetrical ptosis is the single most characteristic physical sign of myasthenia gravis. Watching it worsen on sustained upgaze, and recover after rest or an ice pack, turns a vague complaint of tiredness into a neuromuscular junction diagnosis at the bedside.
Inspect eye movements: The eyes are not aligned, one eye is deviated and fails to move fully with the other, producing an obvious squint and dysconjugate gaze. The pattern does not fit any single cranial nerve territory, and it varies from moment to moment as he fatigues. Why it helps: complex ophthalmoplegia that crosses cranial-nerve boundaries and fluctuates is the signature of a neuromuscular junction disorder rather than a third, fourth or sixth nerve palsy. It explains his intermittent diplopia after reading or driving.
Inspect the face: Eye closure is weak: you can prise the lids open against his effort, and the eyelashes are not buried.
Inspect the work of breathing: He is breathing 24 times a minute, using the accessory muscles of the neck, speaking in short broken phrases and unable to complete a sentence or to count past about 12 on one breath. Lying flat he becomes distressed, and the abdomen moves paradoxically inwards on inspiration. His SpO2 still reads 97%. Why it helps: the most safety-critical observation in this case. In neuromuscular respiratory failure the oxygen saturation stays normal until the patient is about to arrest, the pulse oximeter is falsely reassuring.
Inspect the neck: The head hangs forward on the chest and he cannot hold it up, he props his chin on his hand or lets the head rest back against the chair. Lifting the head off the pillow is impossible after a few seconds (dropped head from neck extensor weakness). Why it helps: neck extensor weakness travels with diaphragmatic weakness, a dropped head in myasthenia is a warning sign of impending respiratory failure and should prompt immediate FVC measurement and escalation, not reassurance.
Inspect the patient's posture and position: He is sitting bolt upright and leaning forward, refusing to lie back on the trolley, with his head supported on his hand and his elbows on his knees. He becomes visibly worse and more breathless the moment the trolley is reclined. Why it helps: orthopnoea in a patient with no cardiac history is diaphragmatic weakness until proved otherwise. The posture he has chosen for himself is itself a vital sign, and it points to the same impending crisis as the falling FVC.

Imaging findings

MRI brain: Normal, no brainstem lesion, no demyelination, no mass.

Why the diagnosis is myasthenia gravis

The decisive diagnosis is myasthenia gravis, now progressing to myasthenic crisis. the central lesson is fatiguability: weakness that is best on waking and worsens with USE and through the DAY, improving with rest. Because 'worse when tired' sounds like ordinary tiredness, patients are dismissed as stressed or run down for months, as here. The pattern is ocular (fluctuating ptosis and diplopia), bulbar (nasal/slurred speech that worsens as they talk, chewing difficulty, choking) and proximal limb weakness, with completely normal sensation and preserved reflexes (this is how you separate it from Guillain, Barré, which is areflexic and often has sensory symptoms). Demonstrate fatiguability at the bedside, sustained upgaze, counting aloud, the ice-pack test. Confirm with acetylcholine receptor antibodies (or anti-MuSK if negative) and repetitive nerve stimulation showing a decremental response. always do a CT chest to look for a thymoma. 'Peripheral neuropathy' is the wrong-compartment label this case punishes, the defect is at the neuromuscular junction.

Myasthenia gravis at a glance

What it is

Myasthenia gravis is an autoimmune disease in which antibodies attack the acetylcholine receptors at the neuromuscular junction, the point where a nerve ending meets a muscle fibre. With fewer working receptors, each nerve impulse produces a weaker muscle contraction, and repeated use exhausts the remaining receptors further, so weakness characteristically worsens through the day and improves with rest.

Pathogenesis

Most patients have IgG antibodies against the post-synaptic acetylcholine receptor itself; a minority instead have antibodies against MuSK, a protein that helps cluster those receptors. Either way, normal neuromuscular transmission fails progressively with repeated stimulation.

Who it affects

Uncommon: roughly 15 to 20 cases per 100,000. It shows two peaks, women in their 20s to 30s, and men in their 60s to 70s, often associated with a thymoma in the older group. Around 10 to 15% of patients have a thymoma, and it can occur alongside other autoimmune diseases such as thyroid disease.

How serious it is

Some drugs and infections can precipitate a crisis in a previously stable patient.

Causes and risk factors

Myasthenia gravis is an acquired autoimmune disease, not inherited in a simple pattern, though other autoimmune conditions in the patient or family raise the background risk. Thymic hyperplasia or thymoma is present in most patients and is thought to drive the abnormal antibody production.

Investigations and lab tests

Bedside clues include fatiguable ptosis on sustained upgaze, worsening dysarthria on counting aloud, and improvement of ptosis after an ice pack over the eyelid. Acetylcholine receptor antibodies confirm the diagnosis in most patients; anti-MuSK antibodies are checked if negative. Repetitive nerve stimulation shows a decremental response with repeated stimulation. A CT chest is performed to look for a thymoma.

At a glance: Confirm: acetylcholine receptor antibodies (anti-MuSK if negative). Demonstrate: repetitive nerve stimulation, decremental response. Always: CT chest for thymoma.

Teaching points

Myasthenia gravis is defined by fatiguability, weakness that is best on waking and worsens with use and through the day, improving with rest.
Because 'worse when tired' sounds like ordinary tiredness, these patients are commonly dismissed as stressed or run down for months.
The pattern is ocular (fluctuating ptosis, diplopia), bulbar (nasal/slurred speech worsening as they talk, chewing difficulty, choking) and proximal limb weakness.
Sensation is normal and reflexes are preserved, this separates it from Guillain-Barré (areflexic, often sensory) and from neuropathy.
Demonstrate fatiguability at the bedside: sustained upgaze to provoke ptosis, counting aloud to provoke dysarthria, and the ice-pack test.
Confirm with acetylcholine receptor antibodies (anti-MuSK if negative) and repetitive nerve stimulation showing a decremental response.

Practise a similar case

Reading a tidy case is different from taking a history yourself when the clock is ticking. Under a little pressure it is easy to miss the pattern, such as whether the drooping lid and double vision worsen with use or if they choke on drinks. Now try asking the questions yourself with another simulated patient.

Here's one from the same specialty, with the diagnosis left for you to find. Your next patient is 41, with 2 weeks of worsening headache, a weak right arm, and a fit this morning. Take this patient's history in Diagnosica. It's free to start, no card needed.

Myasthenia gravis case presentation: history, findings and tests