Match each complex patient clinical presentation with the most appropriate, highly specific initial or confirmatory diagnostic laboratory test to establish the diagnosis.
- A 34-year-old woman presents with acute, severe diffuse abdominal pain without rebound tenderness. She recently developed proximal muscle weakness in her arms and hyponatremia (sodium 122 mEq/L) following a course of trimethoprim-sulfamethoxazole.Spot urine porphobilinogen (PBG)
- A 48-year-old man with a history of untreated hepatitis C virus infection presents with painless, fluid-filled vesicles and crusting on the dorsum of both hands that worsen with sun exposure, accompanied by facial hypertrichosis.Total plasma porphyrins
- A 42-year-old man presents with episodic severe facial flushing, abdominal cramping, and unprovoked syncope. Examination reveals a diffuse, hyperpigmented maculopapular rash that rapidly forms pruritic wheals when firmly stroked by a tongue depressor.Serum tryptase
- A 56-year-old woman presents with unintentional weight loss and a painful, coalescing, erythematous rash with central clearing and crusting on her lower extremities. Laboratory tests reveal a new-onset fasting blood glucose of 145 mg/dL.Fasting serum glucagon
- A 38-year-old man presents with recurrent nephrolithiasis and chronic dyspepsia. Upper endoscopy reveals multiple ulcerations in the duodenum and proximal jejunum despite maximal proton pump inhibitor therapy. Serum calcium is 11.2 mg/dL.Fasting serum gastrin
Answer
The correct pairings match Acute Intermittent Porphyria to spot urine PBG, Porphyria Cutanea Tarda to total plasma porphyrins, Systemic Mastocytosis to serum tryptase, Glucagonoma to fasting serum glucagon, and Zollinger-Ellison syndrome (Gastrinoma) to fasting serum gastrin.
Each clinical vignette provides a classic, highly specific presentation of a metabolic or neuroendocrine disorder that requires a targeted biochemical laboratory test. Accurate test selection relies on distinguishing overlapping symptoms (e.g., AIP versus PCT; Systemic Mastocytosis versus Carcinoid; Glucagonoma versus Gastrinoma) by recognizing hallmark physical exam findings and historical clues.
Step-by-Step Solution
Key Concept
Selecting specific biochemical assays for rare metabolic and neuroendocrine disorders based on precise recognition of their distinct paraneoplastic and dermatologic clinical phenotypes.