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Difficulty: HardOrdering Laboratory Tests

A 47-year-old man presents to the primary care clinic complaining of progressive fatigue, decreased libido, and joint pain for the past 8 months. The joint pain primarily affects his hands. He has no significant past medical history and takes no medications. He drinks one or two beers on weekends and does not use tobacco or illicit drugs. Vital signs are within normal limits. Physical examination reveals a bronze hue to his skin, primarily on sun-exposed areas, and mild hepatomegaly. There is bony enlargement and tenderness over the second and third metacarpophalangeal joints bilaterally. Initial laboratory tests show:

Laboratory TestResultReference Range
AST58 U/L10 - 40 U/L
ALT64 U/L10 - 40 U/L
Fasting blood glucose118 mg/dL70 - 99 mg/dL

Which of the following is the most appropriate next step in laboratory evaluation?

  1. Serum transferrin saturation and ferritinAnswer
  2. B
    HFE gene mutation analysis
  3. C
    Antinuclear antibody and cyclic citrullinated peptide antibodies
  4. D
    Hepatitis B surface antigen and hepatitis C antibody
  5. E
    Early morning total serum testosterone

Answer

Serum transferrin saturation and ferritin
The patient's clinical presentation—fatigue, bronze skin hyperpigmentation, decreased libido (secondary to iron deposition in the pituitary), hepatomegaly with mild transaminitis, and characteristic arthropathy of the second and third metacarpophalangeal (MCP) joints—is the classic presentation of hereditary hemochromatosis. The most appropriate initial laboratory step is to demonstrate phenotypic iron overload. This is accomplished by measuring serum transferrin saturation and serum ferritin levels. A transferrin saturation >45% is highly sensitive for the disease. Only after iron overload is biochemically confirmed should the physician proceed to confirmatory genetic testing.

Step-by-Step Solution

1
Analyze the clinical presentation for a unifying diagnosis.
The combination of fatigue, hepatomegaly, bronze skin, specific arthropathy (2nd/3rd MCP joints), and hypogonadism (decreased libido) points strongly to hereditary hemochromatosis.
Recognizing pattern presentation prevents premature closure on isolated symptoms like joint pain or mild transaminitis.
2
Identify the standard diagnostic pathway for the suspected condition.
The initial diagnostic step for hereditary hemochromatosis is demonstrating phenotypic iron overload.
Guidelines recommend biochemical screening prior to targeted genetic testing.
3
Select the appropriate laboratory test to execute the screening step.
Serum transferrin saturation and ferritin levels are ordered.
A transferrin saturation >45% with an elevated ferritin level warrants subsequent confirmatory HFE gene mutation analysis.

Key Concept

The initial laboratory evaluation for patients with suspected hereditary hemochromatosis is biochemical screening with serum transferrin saturation and ferritin levels, followed by confirmatory HFE gene mutation analysis if iron overload is present.
Estimated Time:1m 30s
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Ordering Laboratory Tests

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