Match each patient's clinical presentation with the most appropriate initial targeted laboratory evaluation.
- A 45-year-old man with a 3-month history of progressive proximal muscle weakness and an erythematous rash over his metacarpophalangeal joints.Serum creatine kinase and aldolase levels
- A 62-year-old woman presenting with new-onset unilateral headache, scalp tenderness, and jaw pain while chewing food.Erythrocyte sedimentation rate and C-reactive protein
- A 28-year-old woman with treatment-resistant hypertension, unexplained hypokalemia, and a recently discovered adrenal nodule.Plasma aldosterone concentration to plasma renin activity ratio
- A 55-year-old man with new-onset erectile dysfunction, progressive fatigue, skin hyperpigmentation, and hepatomegaly.Serum transferrin saturation and ferritin levels
- A 32-year-old woman with episodic palpitations, paroxysmal diaphoresis, and severe headaches during acute hypertensive episodes.Plasma fractionated free metanephrines
Answer
Dermatomyositis matches with creatine kinase and aldolase; Giant cell arteritis matches with ESR and CRP; Primary hyperaldosteronism matches with aldosterone-renin ratio; Hemochromatosis matches with transferrin saturation and ferritin; Pheochromocytoma matches with fractionated metanephrines.
Establishing a precise diagnosis begins with matching the patient's syndromic presentation to a focused laboratory workup. Muscle inflammation in dermatomyositis elevates creatine kinase and aldolase. Vascular inflammation in giant cell arteritis elevates ESR and CRP. Autonomous adrenal aldosterone secretion suppresses renin, resulting in an elevated aldosterone-renin ratio. Iron tissue deposition in hemochromatosis drastically increases transferrin saturation and ferritin. Finally, catecholamine-secreting tumors like pheochromocytomas elevate circulating plasma metanephrines. Ordering these specific initial tests is critical before pursuing confirmatory imaging or biopsies.
Step-by-Step Solution
Key Concept
Selecting the most appropriate initial laboratory evaluation requires identifying the underlying pathophysiologic syndrome based on classic clinical vignettes.