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Difficulty: MediumOrdering Laboratory Tests

A 54-year-old man presents to the primary care clinic reporting a 6-month history of fatigue and dull, aching pain in his hands, specifically involving the second and third metacarpophalangeal joints. He also reports new-onset erectile dysfunction and increased urinary frequency over the past three months. He has no significant past medical history and takes no medications. Vital signs are within normal limits. Physical examination reveals mild hepatomegaly and a grayish-bronze hyperpigmentation on the sun-exposed areas of his face and arms. Bilateral firm enlargement of the second and third metacarpophalangeal joints is noted without significant warmth or erythema. Which of the following is the most appropriate next step in laboratory evaluation?

  1. Measurement of transferrin saturation and serum ferritinAnswer
  2. B
    HFE gene mutation analysis
  3. C
    Anti-cyclic citrullinated peptide antibodies
  4. D
    Hemoglobin A1c and fasting lipid panel
  5. E
    Magnetic resonance imaging of the abdomen

Answer

Measurement of transferrin saturation and serum ferritin
The correct answer is measurement of transferrin saturation and serum ferritin. This patient's presentation of fatigue, specific arthropathy (involving the 2nd and 3rd metacarpophalangeal joints), hepatomegaly, skin hyperpigmentation, and signs of new endocrinopathy (erectile dysfunction, possible diabetes mellitus causing polyuria) is highly suspicious for hereditary hemochromatosis. The most appropriate initial diagnostic step for suspected hemochromatosis is biochemical screening with a fasting serum transferrin saturation and serum ferritin. A transferrin saturation greater than 45% is a highly sensitive initial screening threshold that warrants further confirmatory genetic testing.

Step-by-Step Solution

1
Analyze the clinical presentation, noting arthropathy of the 2nd and 3rd metacarpophalangeal joints, hepatomegaly, skin hyperpigmentation, and signs of endocrinopathy (erectile dysfunction, polyuria).
Recognize the classic multisystem presentation of hereditary hemochromatosis ('bronze diabetes').
Identifying the unifying syndrome is required to guide appropriate diagnostic testing.
2
Determine the appropriate diagnostic sequence for suspected hereditary hemochromatosis.
Identify that biochemical testing with iron studies is the first-line diagnostic approach.
Transferrin saturation and serum ferritin are highly sensitive, cost-effective initial screening tests before proceeding to more expensive confirmatory genetic testing.

Key Concept

Initial laboratory screening for hereditary hemochromatosis is performed by measuring serum transferrin saturation and ferritin levels.
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Ordering Laboratory Tests

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