Correct Answer: A. Myasthenia gravis
Myasthenia gravis (MG) is a neuromuscular junction disorder characterized by antibodies against nicotinic acetylcholine receptors (AChR), leading to impaired neuromuscular transmission. The clinical presentation is pathognomonic: fatigability that worsens with activity and improves with rest is the hallmark feature. The patient's triad of ptosis, dysarthria, and dysphagia reflects involvement of extraocular muscles, bulbar muscles, and pharyngeal muscles—the most commonly affected groups in MG. The ocular and bulbar symptoms appearing together with generalized fatigue strongly suggest MG over other neuromuscular disorders. In India, MG affects 1–2 per 100,000 population and is the most common acquired disorder of the neuromuscular junction. Diagnosis is confirmed by edrophonium (Tensilon) test (though less common now), anti-AChR antibodies, or repetitive nerve stimulation (RNS) showing decremental response. Single-fiber electromyography (SFEMG) is the most sensitive test. Management follows Indian guidelines: anticholinesterases (pyridostigmine 60 mg TDS), immunosuppression (prednisolone, azathioprine), and thymectomy if indicated. The ice pack test (improvement of ptosis after ice application for 2–3 minutes) is a simple bedside screening tool widely used in Indian clinical practice.
Why the other options are wrong
B. Duchenne muscular dystrophy — DMD is an X-linked recessive muscular dystrophy presenting in childhood (age 3–5 years) with progressive proximal muscle weakness, not in a 30-year-old adult. Critically, DMD shows no fatigability pattern—weakness is constant and progressive, not improving with rest. Ptosis and bulbar symptoms are late features, not early presentation. The absence of the characteristic fatigue-rest cycle rules out DMD. C. Lambert-Eaton syndrome — Lambert-Eaton myasthenic syndrome (LEMS) is a presynaptic disorder (anti-VGCC antibodies) presenting with proximal muscle weakness that improves with activity (opposite of MG's pattern). LEMS typically shows autonomic symptoms (dry mouth, constipation, impotence) and is strongly associated with small-cell lung cancer in adults. The improvement with activity and absence of ocular/bulbar symptoms early on distinguish LEMS from MG. D. Systemic lupus erythematosus — SLE is a multisystem autoimmune disorder presenting with constitutional symptoms (fever, rash, arthralgia, photosensitivity), not isolated neuromuscular symptoms. While SLE can cause myositis or neuropsychiatric manifestations, the specific triad of fatigability improving with rest, ptosis, and bulbar dysfunction is not characteristic of SLE. The clinical pattern is too focal and too specific for a systemic connective tissue disease.
High-Yield Facts
- Fatigability improving with rest is the pathognomonic feature of myasthenia gravis; worsening with activity distinguishes it from Lambert-Eaton syndrome.
- Ocular and bulbar symptoms (ptosis, dysarthria, dysphagia) are the most common early manifestations of MG, appearing in >90% of patients.
- Anti-AChR antibodies are positive in 80–90% of generalized MG and 50% of ocular MG; RNS shows decremental response in 60–70% of generalized MG.
- Edrophonium (Tensilon) test (short-acting anticholinesterase) produces rapid improvement in MG symptoms; ice pack test is a simple bedside alternative.
- Thymoma is present in 10–15% of MG patients in India; thymectomy is indicated in thymoma-associated MG and improves remission rates.
- Pyridostigmine (anticholinesterase) is first-line symptomatic treatment; immunosuppression (prednisolone, azathioprine) is used for disease modification.
Mnemonics
MG Triad: REST Rest improves symptoms | Extraocular & bulbar early | Symptoms worsen with activity | Treatment: anticholinesterase + immunosuppression LEMS vs MG: Activity Effect MG: activity worsens, rest improves | LEMS: activity improves, rest worsens (opposite pattern). LEMS = presynaptic (VGCC), MG = postsynaptic (AChR).
NBE Trap
NBE pairs "fatigability" with "muscular dystrophy" to trap students who confuse progressive weakness with activity-dependent fatigue. The key discriminator is improvement with rest—this rules out all primary myopathies and points to neuromuscular junction pathology.
Clinical Pearl
In Indian outpatient practice, the ice pack test (applying ice over closed eyelid for 2–3 minutes and observing improvement in ptosis) is a rapid, cost-free screening tool for MG that avoids the need for immediate antibody testing. Many district hospitals in India use this before referral for confirmatory testing.
_Reference: Harrison Ch. 381 (Myasthenia Gravis); Robbins Ch. 27 (Neuromuscular Disorders)_