USMLE Forum Archives - USMLE Step 1 - Pathology 9
Pathology 9
TheOne - 10-01-06 14:17
A 25-year-old male reports episodic "spells" characterized by palpitations, sweating, nervousness, and feelings of anxiety. On examination, the man's blood pressure is 165/95 mm Hg. Plasma norepinephrine is 450 pg/mL (normal, 150-400 pg/mL), plasma epinephrine is 115 pg/mL (normal, 25-100 pg/mL), and 24-hour urinary VMA is 11 mg (normal, < 8 mg). Which of the following is the most likely cause of the patient's hypertension?
A. 11-beta-hydroxylase deficiency
B. Conn's syndrome
C. Pheochromocytoma
D. Renin-secreting tumor
E. Unilateral renal artery stenosis
TheOne - 10-01-06 14:17
A 25-year-old male reports episodic "spells" characterized by palpitations, sweating, nervousness, and feelings of anxiety. On examination, the man's blood pressure is 165/95 mm Hg. Plasma norepinephrine is 450 pg/mL (normal, 150-400 pg/mL), plasma epinephrine is 115 pg/mL (normal, 25-100 pg/mL), and 24-hour urinary VMA is 11 mg (normal, < 8 mg). Which of the following is the most likely cause of the patient's hypertension?
A. 11-beta-hydroxylase deficiency
B. Conn's syndrome
C. Pheochromocytoma
D. Renin-secreting tumor
E. Unilateral renal artery stenosis
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#2
Re: Pathology 9
TheOne - 10-03-06 13:01 Explanation: The correct answer is C. A pheochromocytoma is a tumor arising from chromaffin cells that secretes excess catecholamines (norepinephrine, epinephrine, or both). It is one endocrine cause of hypertension, due to peripheral vasoconstriction and/or increased cardiac output. While most patients have higher than normal baseline plasma levels of catecholamines, it is not uncommon for paroxysmal symptomatic episodes to be superimposed upon the basal problem. These "attacks" may occur several times a week (or more often) and last for up to 15 minutes. During an attack, respiration can increase, the patient may become aware of a forceful pounding of the heart that progresses to include a throbbing headache, and peripheral vasoconstriction can raise body temperature and lead to reflex sweating. Marked anxiety may also accompany the episode. Diagnosis can be confirmed by measuring increased plasma or urinary catecholamines or their metabolites. 11-beta-hydroxylase deficiency (choice A) is a congenital disorder than can cause hypertension due to excessive production of the weak mineralocorticoid, deoxycorticosterone, by the inner two zones of the adrenal cortex. This results in excessive renal retention of sodium and water and subsequent hypertension. While the hypertension is usually present from birth, a late-onset variant of this disorder has been described in which the symptoms do not present until late childhood or adolescence. Virilization is also present due to excessive secretion of adrenal androgens. Conn's syndrome (choice B) is another endocrine cause of hypertension. In this case, the increase in blood pressure is due to excessive renal retention of sodium and water resulting from the increased plasma concentration of aldosterone. The paroxysmal symptoms and increased catecholamines present in this patient are not present with primary hyperaldosteronism. Renin-secreting tumors (choice D) are rare and can be confused with primary hyperaldosteronism. The excessive secretion of renin by the tumor can increase the formation of angiotensin II with subsequent hyperaldosteronism. Sodium and water retention, together with hypokalemia, are present. Increased plasma renin and plasma aldosterone are suggestive of a renin-secreting tumor, whereas primary hyperaldosteronism would present as increased plasma aldosterone, but decreased plasma renin. Unilateral renal artery stenosis (choice E) produces an angiotensin II-dependent form of hypertension. Decreased renal perfusion, often due to atherosclerosis or fibromuscular hyperplasia of the renal arteries, results in increased renin secretion and subsequently increased plasma angiotensin II. The resultant increase in aldosterone secretion and arteriolar vasoconstriction contributes to the hypertension.
#3
Re: Pathology 9 galaxy - 05-27-10 18:56 elevated serum epinephrine,norepinephrine and urinary VMA....with hypertension are all suggestive of phaeochromacytoma...a tumor of the adrenal medulla...
#4
Re: Pathology 9 babbu5508 - 06-21-10 14:46 C. Pheochromocytoma as evidenced by increased plasma epinephrine,norepinephrine and urinary vanillyl mandelic acid which are diagnostic
#5
Re: Pathology 9 bingousmle - 06-30-10 22:42 pheochromocytoma chromaffin cells that secretes excess catecholamines (norepinephrine, pinephrine, or both). It is one endocrine cause of hypertension, due to peripheral vasoconstriction and/or increased cardiac output.
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