Pediatrics · Year 3 · from Pediatrics

Case 2: Cow's Milk Protein Allergy

Patient Demographics

  • Age: 6-week-old male
  • Sex: Male

Chief Complaint

"My baby has blood in his stool and is very fussy."

History of Present Illness

A 6-week-old formula-fed male presents with blood-streaked stools noticed over the past week. Mother reports the infant has been increasingly fussy, especially during and after feeds, with frequent spitting up and what appears to be abdominal discomfort (drawing legs up, crying). Stools have been mucousy and loose with visible streaks of blood. He was switched from breastfeeding to cow's milk-based formula at 2 weeks of age due to maternal medication use. There is no fever, lethargy, or decrease in feeding volume. He is taking 4 oz every 3 hours. Family history is notable for eczema in mother and food allergies in an older sibling.

Growth Parameters

  • Birth weight: 3.5 kg (50th percentile)
  • Current weight: 4.3 kg (35th percentile)
  • Length: 54 cm (50th percentile)
  • Head circumference: 37 cm (50th percentile)

Physical Examination

  • General: Fussy but consolable infant, mild perianal erythema
  • HEENT: No oral lesions
  • Cardiovascular: Normal
  • Respiratory: Clear
  • Abdomen: Soft, mildly distended, hyperactive bowel sounds, no masses or hepatosplenomegaly
  • Rectal: Grossly bloody mucoid stool on diaper, no fissures
  • Skin: Mild eczematous patches on cheeks and antecubital fossae
  • Neurologic: Normal tone, age-appropriate reflexes

Workup

  • Stool studies:
  • Guaiac: Positive
  • Stool culture: Negative
  • Ova and parasites: Negative
  • Stool reducing substances: Negative
  • CBC: WBC 12,000, Hgb 11.2, Platelets 380,000, eosinophils 8% (elevated)
  • Stool eosinophils: Present (on smear)
  • Total IgE: Mildly elevated
  • CMP: Normal

Diagnosis

Cow's milk protein allergy (non-IgE mediated/food protein-induced allergic proctocolitis)

Clinical Reasoning

The presentation of bloody, mucousy stools in a formula-fed infant with fussiness, eczema, family history of atopy, and peripheral eosinophilia is classic for cow's milk protein allergy. The non-IgE mediated form (allergic proctocolitis) typically presents at 2-8 weeks with blood-streaked stools and is more common than IgE-mediated allergy in this age group. The absence of systemic symptoms, adequate growth, and reassuring exam argue against more serious conditions like intussusception, necrotizing enterocolitis, or infectious colitis.

Management

  1. Dietary elimination:
  • Switch to extensively hydrolyzed formula (e.g., Alimentum, Nutramigen)
  • If symptoms persist after 2-4 weeks, trial amino acid-based formula (e.g., EleCare, Neocate)
  1. Expected response:
  • Occult blood may resolve in 72-96 hours
  • Gross blood typically resolves in 1-2 weeks
  • Fussiness improves within 2-4 weeks
  1. Follow-up:
  • Weight check in 1-2 weeks
  • Clinical reassessment at 4 weeks
  1. Reintroduction:
  • Can trial milk protein reintroduction at 9-12 months (most outgrow by age 1)
  • Perform in office if IgE-mediated symptoms develop
  1. Parent education:
  • Avoid introducing cow's milk products in complementary foods
  • Most children outgrow this by 12 months

Clinical Image

Image Description: Photograph of infant stool demonstrating mucus and blood streaks characteristic of cow's milk protein allergy.

Source: Wikimedia Commons URL: https://commons.wikimedia.org/wiki/File:Milk_protein_allergy_stool.jpg License: CC BY-SA 4.0

All cases for this lecture as Markdown