A 1-month-old boy is brought to the office for follow-up of blood-streaked stools and diarrhea. The patient was born preterm at 35 weeks gestation and had no complications in the newborn nursery. He had been taking a standard cow's milk–based formula until 2 weeks ago when he developed loose stools streaked with blood and mucus. Symptoms resolved after changing the formula. If histopathologic examination had been performed when the patient was symptomatic, which of the following would most likely be seen?
Food protein–induced allergic proctocolitis | |
Pathophysiology |
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Clinical features |
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Treatment & prognosis |
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This patient most likely has food protein–induced allergic proctocolitis, a benign condition of early infancy (age <6 months). Affected infants have a non–IgE-mediated reaction to proteins found in breast milk or formula (most common trigger is cow's milk). Painless, blood-streaked stools (which may also be loose and contain mucus) typically develop weeks to months after initial exposure to the food allergen.
Diagnosis is clinical. Although endoscopy is not performed unless symptoms are atypical (eg, severe bleeding, constipation, vomiting), characteristic findings include inflammation (ie, erythema, edema) confined to the distal colon and rectum. Histopathology findings include infiltration of eosinophils within the lamina propria and muscularis mucosa.
Management includes dietary avoidance of the trigger protein (eg, switching to a hydrolyzed formula, maternal elimination of dairy for breastfed infants). Symptoms typically resolve within weeks, and most infants can tolerate the offending protein by age 1.
(Choice B) Hemorrhagic necrosis of the bowel wall describes necrotizing enterocolitis, a gastrointestinal emergency that can result in gut ischemia and death if untreated (eg, bowel rest, antibiotics). In addition to rectal bleeding, patients often have abdominal distension, poor feeding, and hemodynamic instability, none of which is present in this patient.
(Choices C and D) A Meckel diverticulum can contain heterotopic gastric mucosa in the distal ileum, and neutrophilic crypt abscesses can be seen with ulcerative colitis. Although these conditions, which are both exceedingly rare in the neonatal period, can cause blood in the stool, neither would resolve with a change in formula.
Educational objective:
Food protein–induced allergic proctocolitis is a non–IgE-mediated reaction that causes inflammation and eosinophilic infiltration of the distal colon. Classic presentation is in early infancy with painless, blood-streaked stools that resolve with dietary avoidance of the offending food protein (eg, cow's milk).