[Psychomotor regression due to vitamin B₁₂ deficiency]

The vitamin B₁₂ reserves of newborns are dependent on transplacental transfer and secondarily on food intake. This vitamin is involved in hematopoiesis and in neurological development. We report the case of a severe vitamin B₁₂ deficiency in a 7-month-old infant. A neurological evaluation performed at 5 months of age for psychomotor regression found nonspecific cortical atrophy. The infant was hospitalized for impaired general condition and worsening of neurological symptoms. Examinations revealed bicytopenia with normocytic anemia (Hb: 7.4g/dl, MCV : 84μm³). The combination of psychomotor regression, malnutrition, and anemia suggested there was a deficiency, specifically of vitamin B₁₂ (blood values of < 50pg/mL, normal range=200-1000); bone marrow aspiration showed characteristics of megaloblastic dystrophy. Psychomotor regression associated with hematological disorders and a failure to thrive can be related to vitamin B₁₂ deficiency. Replacement therapy must be established as early as possible to avoid potentially irreversible neurological damage.