Cow's-milk protein allergy — formative SAQs

SAQ 1 (10)

A 5-month-old formula-fed infant presents with a 3-week history of blood and mucus in the stools. The infant is well-looking, afebrile, feeding normally, and growing along the 50th centile. There is no vomiting, no rash, and no respiratory symptoms. ^{[1] [2]}

1. State the most likely diagnosis and the single investigation you would use to confirm it. (3) ^[1]
2. Outline your initial management, including the feeding change you would make. (4) ^{[1] [2]}
3. Describe the prognosis and the plan you would give the family for reintroduction. (3) ^{[1] [4]}

Model answer

Diagnosis and confirmation. The most likely diagnosis is cow's-milk protein-induced proctocolitis, the commonest non-IgE-mediated phenotype of cow's-milk protein allergy, presenting as blood and mucus in the stools of an otherwise well, thriving infant. Confirmation is clinical: I would not order skin-prick or specific IgE, because these are typically negative in non-IgE disease. I would eliminate cow's-milk protein for two to four weeks and confirm the diagnosis by resolution of symptoms, then a planned reintroduction that reproduces them. ^[1]

Initial management. Switch from standard cow's-milk formula to an extensively hydrolysed formula as first-line. The family should expect the bleeding to settle within two to four weeks. No antibiotics, no invasive investigation, and no restrictive work-up are required in this well-looking, growing infant. I would also assess the family's understanding of what elimination means and arrange dietetic input if there is any concern about nutrition, though an extensively hydrolysed formula is nutritionally complete. ^{[1] [2]}

Prognosis and reintroduction. The prognosis is excellent: most infants with proctocolitis tolerate cow's milk by their first birthday. I would plan a structured milk ladder or a planned reintroduction from around nine to twelve months, beginning with baked milk. I would reassure the family that this is a benign, well-looking pattern that needs no invasive tests and that the outlook is resolution, while giving a clear safety-net to return if symptoms recur or growth falters. ^{[1] [4]}