A 28-year-old woman comes to the office due to weakness. The patient, who is 8 weeks postpartum, reports intermittent weakness of the upper and lower extremities. She says, "My arms feel weak after carrying the baby for a few minutes, and I can't lift him until I rest for some time. Yesterday evening, I couldn't even get off of the toilet, but today, I feel fine." The patient has also had episodes of blurry vision. Her pregnancy was complicated by gestational diabetes, but she has no chronic medical conditions. The patient's only medication is a daily multivitamin. She does not use tobacco, alcohol, or illicit drugs. Blood pressure is 120/68 mm Hg and pulse is 74/min. Physical examination shows normal pupils and extraocular movements. Jugular venous pressure is not elevated, and chest auscultation reveals no abnormalities. There is no extremity edema. Deep tendon reflexes and muscle strength of the bilateral upper and lower extremities are normal. Which of the following is the most likely diagnosis?

Question

A 28-year-old woman comes to the office due to weakness.  The patient, who is 8 weeks postpartum, reports intermittent weakness of the upper and lower extremities.  She says, "My arms feel weak after carrying the baby for a few minutes, and I can't lift him until I rest for some time.  Yesterday evening, I couldn't even get off of the toilet, but today, I feel fine."  The patient has also had episodes of blurry vision.  Her pregnancy was complicated by gestational diabetes, but she has no chronic medical conditions.  The patient's only medication is a daily multivitamin.  She does not use tobacco, alcohol, or illicit drugs.  Blood pressure is 120/68 mm Hg and pulse is 74/min.  Physical examination shows normal pupils and extraocular movements.  Jugular venous pressure is not elevated, and chest auscultation reveals no abnormalities.  There is no extremity edema.  Deep tendon reflexes and muscle strength of the bilateral upper and lower extremities are normal.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec25c8_d576_9d33_bc81_6956db2a591d_MD0003_00 This young, postpartum woman has fatigable proximal muscle weakness and intermittent blurred vision, findings suggestive of myasthenia gravis (MG). MG is a neuromuscular disorder characterized by autoantibodies directed at components of the postsynaptic neuromuscular junction, typically acetylcholine receptors. It is most common in women of childbearing age; in addition, pregnant and postpartum women are at increased risk for both disease onset and exacerbation. Men are less frequently affected and typically develop symptoms later in life (ie, sixth to eighth decade). MG is characterized by fluctuating, fatigable muscle weakness that worsens with repetitive motions (eg, holding a baby for a prolonged period) and improves with rest. Symptoms are frequently worse later in the day or after exercise. Proximal muscle involvement (eg, hip flexors, quadriceps, deltoids) can cause difficulty rising from sitting or lifting over the head. Bulbar (eg, dysarthria, fatigable chewing) and ocular dysfunction (eg, blurred vision, ptosis) are also common. Although examination eventually demonstrates fatigable weakness with repetitive activity, it is often normal on initial evaluation. (Choice A) Diabetic amyotrophy typically causes focal pain, weakness, and muscle wasting in the proximal legs; it is associated with weight loss. Upper extremity involvement is rare and would not be associated with vision changes or fluctuating weakness. (Choice B) Multiple sclerosis is common in younger women and can cause neurologic symptoms (eg, weakness, blurred vision) in discrete, noncontiguous domains. However, symptoms typically relapse and remit slowly over days to weeks; fatigable weakness that fluctuates throughout the day is more consistent with MG. (Choice D) Myotonic dystrophy typically causes persistent, progressive weakness and wasting of the facial and distal musculature (eg. intrinsic hand). Myotonia (delayed muscle relaxation after contraction) is typical, and fluctuating proximal muscle weakness is unexpected. (Choices E and F) Myopathies (eg, polymyositis, hyperthyroid myopathy) typically present with persistent, symmetric proximal muscle weakness that may be associated with mild muscle pain and tenderness. However, fluctuating, fatigable weakness and ocular symptoms are not characteristic. In addition, postpartum thyroiditis is typically associated with signs of hyperthyroidism (eg, heat intolerance, weight loss, tremor). Educational objective: Myasthenia gravis is characterized by fluctuating, fatigable muscle weakness that worsens with repetitive motions and improves with rest. Common symptoms include weakness of the proximal (eg, difficulty rising from sitting), ocular (eg, diplopia, ptosis), and bulbar (eg, dysarthria, dysphagia) muscles. Pregnant and postpartum patients are at increased risk for developing the disease. References: Myasthenia gravis: a review. (http://www.ncbi.nlm.nih.gov/pubmed/23193443)

A 28-Year-Old Woman Comes to the Office Due to Weakness