A 52-year-old woman presents with confusion and weakness for the last 2 weeks. Her husband reports that she has had three seizures during this time. She has an insignificant past medical history and her physical examination is unremarkable. Laboratory results reveal the following:
Rapid correction of this patient’s electrolyte abnormality can cause which of the following?
Central pontine myelinolysis. The patient in this question has severely symptomatic hyponatremia (serum sodium <120 mEq/L). This is a medical emergency and prompt correction of the serum sodium concentration with hypertonic (3%) saline should be initiated, while working up the underlying etiology. The maximum rate of serum sodium correction should be 0.5 mEq/L/h; if the rate is corrected too rapidly, then irreversible brain damage can occur from a condition called central pontine myelinolysis. This occurs because such rapid correction of hyponatremia can result in water moving from the intracellular compartment to the extracellular compartment and such altered metabolic activity results in cell damage to the neurons and glia. (A, D) Atrial fibrillation and subarachnoid hemorrhage are not adverse effects of rapid correction of severe hyponatremia. (B) Intracerebral edema can happen when the opposite clinical scenario (rapidly correcting hypernatremia) occurs. This is due to water flowing into brain cells, which causes them to swell.
A 62-year-old man with a longstanding history of chronic obstructive pulmonary disease (COPD) presents for follow-up. The patient is on several medications, including albuterol and ipratropium. He is compliant with his medications, but often gets short of breath with minimal exercise.
Which of the following physiologic changes do you expect in this patient?
Hypoventilation and increased renal bicarbonate reabsorption. This patient likely has a chronic respiratory acidosis secondary to chronic lung disease (COPD). Hypoventilation occurs in COPD due to decreased responsiveness to hypoxia and hypercapnia as well as increased dead space ventilation. This hypoventilation causes retention of PaCO2 (PaCO2 >40 mmHg). The increase in PaCO2 causes a decrease in pH, and the kidney compensates by increasing bicarbonate reabsorption to counteract the decrease in pH in an attempt to bring it back to normal (7.4). (B, C, D) These are not the findings in chronic respiratory acidosis.
A 42-year-old woman presents with headache, rigors, weakness, weight loss, nausea, vomiting, abdominal pain, and new-onset “craving of salty foods.” She is febrile with a temperature of 39.8°C and has a blood pressure of 82/48 mmHg, heart rate of 102 beats per minute, respiratory rate of 24 breaths per minute, and oxygen saturation of 94% on room air. Physical examination reveals dry mucous membranes and diffuse muscle tenderness on palpation. She has cyanosis on her distal extremities and a generalized maculopapular rash with several areas of purpura. Laboratory results reveal the following:
Serum cortisol is lower than expected after ACTH stimulation test.
Which of the following is the most likely diagnosis?
Waterhouse–Friderichsen syndrome (WFS). The patient in this question is presenting with signs and symptoms of adrenal crisis, likely from primary adrenal insufficiency caused by hemorrhagic infarction of the adrenal glands by Neisseria meningitidis, which is called WFS. This bacterial infection can cause massive hemorrhage into one or both of the adrenal glands leading to organ failure, hypotension, and rapidly developing adrenal insufficiency. Given that the ACTH stimulation test did not produce an increase in serum cortisol (as one would expect with normally functioning adrenal glands) in addition to the laboratory findings of hyponatremia and hyperkalemia, primary adrenal insufficiency is the likely diagnosis. The presence of severe sepsis in this patient makes the diagnosis of WFS the most likely.
(A) SIADH would present with hyponatremia, but not hyperkalemia. (B) Withdrawal of exogenous steroids causes a secondary adrenal insufficiency. This would not present with fever and severe sepsis as in this patient. Furthermore, serum cortisol can sometimes increase (even if just a minimal amount) after ACTH stimulation in secondary adrenal insufficiency assuming there is still functional adrenal tissue. (D) Cushing syndrome presents with hypercortisolism, not hyponatremia.
A 29-year-old woman presents with complaints of weight loss, diarrhea, and sweating for the last 6 weeks. She is otherwise healthy and her family history is unremarkable. She has a temperature of 36.8°C, blood pressure of 142/86 mmHg, heart rate of 92 beats per minute, respiratory rate of 24 breaths per minute, and oxygen saturation of 98% on room air. Physical examination reveals moist warm skin and hyperreflexia.
Which of the following is the next best step in management?
Thyroid-stimulating hormone (TSH) levels. The patient in this question is demonstrating clinical manifestations of hyperthyroidism. In approaching the diagnosis of thyroid disorders, the first step is to order a TSH level. TSH is the most sensitive test to detect primary hypothyroidism and hyperthyroidism. Based on the TSH level, additional tests can be performed. (A) Free T4 is important in the diagnostic workup of thyroid disorders and should be the next test ordered if TSH comes back decreased. If free T4 is increased with a decreased TSH level, this is diagnostic of primary hyperthyroidism. If free T4 is decreased with a decreased TSH level, then central hypothyroidism is the diagnosis and the etiology involves the pituitary gland or the hypothalamus. Finally, if free T4 is normal with a decreased TSH, then this is subclinical hypothyroidism. (C) Thyroglobulin is often increased in goiter and hyperthyroidism and is also a tumor marker for thyroid cancer. It is not the best first test in working up thyroid disorders. (D) Radioactive iodine uptake (RAIU) scan is the next best step once primary hyperthyroidism is diagnosed (increased free T4 with decreased TSH) as it can help differentiate causes of hyperthyroidism (Graves vs. multinodular goiter vs. silent thyroiditis).
A 54-year-old woman with a history of type 1 diabetes mellitus and autoimmune thyroid disease presents with weakness, easy fatigability, anorexia, nausea, and vomiting. She has a blood pressure of 82/64 mmHg and physical examination reveals “spotty” hyperpigmentation of her mucous membranes in her oral cavity. Laboratory results reveal a potassium of 6.1 mEq/L and an elevated ACTH level.
Which of the following is the underlying diagnosis in this patient?
Polyglandular autoimmune syndrome type II. The patient in this question is presenting with signs, symptoms, and laboratory findings consistent with primary adrenal insufficiency (adrenal dysfunction, hyperkalemia, and hypotension). We know this is primary adrenal insufficiency because ACTH is elevated as there is no negative feedback on the hypothalamic pituitary axis since the adrenals are not functioning and secreting cortisol. Secondary adrenal insufficiency, on the other hand, is associated with low to normal levels of ACTH. Given that this patient has type 1 diabetes and autoimmune thyroid disease as well, this is diagnostic of polyglandular autoimmune syndrome type II. (C) Polyglandular autoimmune syndrome type I is usually found in children and is associated with mucocutaneous candidiasis, hypoparathyroidism, and adrenal insufficiency. (A) MEN type I is associated with parathyroid hyperplasia, pancreatic neoplasia, and pituitary adenoma. (B) MEN type 2A is associated with medullary thyroid carcinoma, pheochromocytoma, and parathyroid hyperplasia.
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