Q2. Correct answer: A. Reassurance and consideration of cow milk protein soy intolerance with elimination of these antigens in mother's diet.
The differential diagnosis of hematochezia in infants is relatively small. The most likely considerations are anal fissures, vascular malformations, cow milk protein soy intolerance, bleeding diatheses, swallowed maternal blood in the first 1-2 days of life, and necrotizing enterocolitis in preterm infants. In the setting of an otherwise healthy term infant who presents with hematochezia without anorectal malformations, the most likely etiology is cow milk protein soy intolerance. This is an IgG-mediated disorder that does not necessarily construe other predilections to food allergies. Most infants outgrow this by 1 year of life or thereafter. In mother's who are breastfeeding, it is recommended that they eliminate both cow milk and soymilk proteins from their diet. There is a 70% cross-reactivity between cow milk and soymilk proteins. In infants who are formula feeding or those who do not respond to maternal elimination diets, it is recommended that they consume partially hydrolyzed or fully hydrolyzed formula. Such infants are usually able to tolerate cow and soy proteins later in life.
Mäkinen OE et al. Crit Rev Food Sci Nutr. 2016;56(3):339-49.