[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.