Myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disorder of neuromuscular transmission. It causes fluctuating, fatigable weakness of voluntary muscles. Eye and eyelid weakness is common; facial, speech, chewing, swallowing, neck, limb, and breathing muscles may also be affected. Symptoms often worsen with sustained activity and improve with rest, but the pattern varies.1

Urgent safety

A myasthenic crisis is a life-threatening breathing emergency. Seek emergency care for new or worsening shortness of breath, weak cough, inability to handle saliva or secretions, rapidly worsening swallowing, or speech that becomes difficult because of breath or bulbar weakness. Do not wait for a routine appointment or rely on a general webpage to judge severity.2

Medication changes, infection, surgery, pregnancy, and other physiologic stressors can alter MG control. Review all prescription, over-the-counter, and procedural medications with the treating team because some drugs can worsen weakness. Do not stop MG treatment abruptly unless the responsible clinician directs it.1

Diagnosis

Diagnosis combines the history and neurologic examination with tests selected for the presentation. These may include antibodies to acetylcholine receptor (AChR), muscle-specific kinase (MuSK), or other neuromuscular-junction targets; repetitive nerve stimulation or single-fiber electromyography; and chest imaging to evaluate the thymus. Negative initial antibody testing does not by itself exclude MG.1

Autoimmune MG is distinct from congenital myasthenic syndromes, Lambert-Eaton myasthenic syndrome, motor neuron disease, botulism, and other causes of fluctuating weakness. The historical edrophonium test should not be presented as a routine self-contained diagnostic step.

Treatment and follow-up

Treatment is individualized by antibody status, ocular or generalized involvement, thymus findings, disease activity, other health conditions, and personal priorities. Options can include symptomatic acetylcholinesterase inhibition, corticosteroid or other immunotherapy, selected targeted biologic treatment, thymectomy for defined indications, and intravenous immunoglobulin or plasma exchange for severe worsening or crisis.1

This page intentionally does not prescribe a drug sequence. Treatments have different indications, monitoring needs, contraindications, access requirements, and risks. Current guidelines emphasize disease-activity assessment and shared specialist decisions rather than a single regimen for everyone.1

Speech, voice, and swallowing

Bulbar weakness may cause a soft, breathy, hypernasal, or imprecise voice; reduced speech endurance; chewing fatigue; nasal regurgitation; coughing; or difficulty clearing food and secretions. Performance may change during a meal, conversation, or day, so a brief “best” performance can miss clinically important fatigue.

Speech-language and swallowing assessment should document variability and coordinate findings with neurology and respiratory care. Positioning, meal timing, texture, pacing, and compensatory strategies must be selected from direct assessment. Strengthening exercises or voice amplification are not automatic: added effort may worsen fatigable performance for some people.

Communication access

MG does not inherently impair language, literacy, or cognition. When speech becomes unreliable, preserve the person's established language and choose the lowest-effort effective option:

• writing, alphabet boards, stored phrases, text-to-speech, or a speech-generating device;
• an agreed yes/no response and quick access to breathing, suction, pain, positioning, and emergency messages;
• direct touch, an adapted pointer, switches, partner-assisted scanning, or eye gaze based on current performance;
• mounting, positioning, rest breaks, and a low-tech backup.

Access can vary within the same day and may improve after treatment, so avoid locking the person into a diagnosis-based device prescription. AAC can be temporary or part-time and should remain available whenever speech is not efficient or reliable.5 For evaluation, trials, funding, and implementation, use the AAC device acquisition guide.

Coding

• ICD-10-CM G70.00: Myasthenia gravis without acute exacerbation.
• ICD-10-CM G70.01: Myasthenia gravis with acute exacerbation.

Coding must match the documented current condition. A billing code does not determine whether a person is in myasthenic crisis; crisis is a clinical emergency assessment.6

Sources

1. Wiendl et al. Guideline for the management of myasthenic syndromes — diagnosis-informed treatment, disease-activity assessment, thymectomy, targeted therapies, and crisis care (2023; PMID 38152089).
2. National Institute of Neurological Disorders and Stroke: Myasthenia gravis — clinical features and emergency respiratory boundary.
3. MedlinePlus: Myasthenia gravis — emergency description of myasthenic crisis.
4. Narayanaswami et al. International Consensus Guidance for Management of Myasthenia Gravis: 2020 Update — international consensus management guidance (PMID 33144515).
5. American Speech-Language-Hearing Association: Augmentative and Alternative Communication — individualized, multimodal AAC assessment.
6. Centers for Medicare & Medicaid Services: FY2026 ICD-10-CM definitions — G70.00 and G70.01 descriptors.

Review boundary

This guide does not diagnose MG, determine crisis severity, or prescribe treatment, diet, swallowing strategies, or exercise. Breathing and rapidly worsening bulbar symptoms require emergency assessment. Ongoing decisions require direct review by neurology and, when indicated, respiratory and speech-language/swallowing clinicians.