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Difficulty: MediumPediatric Gastrointestinal Disorders

A 44-year-old girl is brought to the pediatric clinic by her mother due to a 66-month history of foul-smelling, bulky stools and poor weight gain. Her mother reports that the child frequently complains of diffuse abdominal discomfort and has become increasingly irritable. The patient's growth chart indicates that her weight has dropped from the 50th50^{\text{th}} percentile to the 10th10^{\text{th}} percentile over the past year, while her height remains tracking at the 40th40^{\text{th}} percentile. Physical examination reveals a visibly distended abdomen and decreased subcutaneous fat in the extremities. Laboratory evaluation demonstrates a hemoglobin of 9.2 g/dL9.2 \text{ g/dL} with a mean corpuscular volume of 72 fL72 \text{ fL}. Which of the following is the most appropriate initial diagnostic step for this patient?

  1. Measurement of serum tissue transglutaminase IgA antibodiesAnswer
  2. B
    Upper gastrointestinal endoscopy with duodenal biopsy
  3. C
    Empiric elimination of lactose from the diet
  4. D
    Reassurance and scheduled follow-up in 66 months
  5. E
    Administration of empiric oral metronidazole

Answer

Measurement of serum tissue transglutaminase IgA antibodies is the best first step.
This patient's presentation of chronic, bulky, foul-smelling stools, failure to thrive (evidenced by her weight dropping multiple major percentiles), abdominal distension, and microcytic anemia is highly suspicious for celiac disease. The initial non-invasive test of choice for suspected celiac disease is the measurement of serum tissue transglutaminase (tTG) IgA antibodies. This test has excellent sensitivity and specificity. It is typically drawn alongside a total serum IgA level to ensure the patient does not have a concurrent selective IgA deficiency, which could cause a false-negative result.

Step-by-Step Solution

1
Analyze the clinical presentation and physical exam findings.
The patient has chronic malabsorptive diarrhea, severe failure to thrive (falling percentiles), and abdominal distension.
These are classic signs of a small bowel mucosal disorder, leading to nutrient malabsorption.
2
Evaluate the laboratory results.
Hemoglobin of 9.2 g/dL and MCV of 72 fL indicate a microcytic anemia.
Microcytic anemia in this context is likely secondary to iron malabsorption in the damaged duodenum, highly characteristic of celiac disease.
3
Determine the appropriate initial diagnostic pathway.
Select non-invasive serologic screening with tissue transglutaminase (tTG) IgA antibodies.
Current guidelines require a highly sensitive serologic test before proceeding to invasive confirmatory procedures like endoscopy.

Key Concept

The initial non-invasive screening step for celiac disease is testing for serum tissue transglutaminase IgA antibodies.
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Topics

Pediatric Gastrointestinal Disorders

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