A 10-month-old exclusively breastfed infant from a strict vegetarian family presents with pallor, developmental regression, hypotonia, and macrocytic anemia (Hb 7.2 g/dL, MCV 108 fL). Serum B12 is critically low at 58 pg/mL. The MOST likely mechanism of B12 deficiency in this breastfed infant is:

• A Congenital intrinsic factor deficiency
• B Selective cobalamin malabsorption due to intestinal disease
• C B12 destruction by prolonged formula heating
• D Transfer of maternal B12 deficiency via breast milk from a vegetarian mother ✓

Explanation

Exclusively breastfed infants of strictly vegetarian/vegan mothers are at high risk for vitamin B12 deficiency because breast milk B12 content directly reflects maternal serum and hepatic B12 stores. Vegetarian/vegan mothers have chronically depleted B12 (found only in animal products) and their milk contains negligible B12. Clinical features include megaloblastic anemia, developmental regression, hypotonia, and if untreated, permanent neurological damage. This is distinct from congenital intrinsic factor deficiency (rare autosomal recessive condition).

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.