Vitamin B12 (B12) deficiency in infancy can present with nonspecific symptoms. We report a 5-month old exclusively breastfed full-term infant with emesis, lethargy, progressive pancytopenia, hemolysis, hypofibrinogenemia, elevated lactate dehydrogenase and a hypercellular bone marrow with dyserythropoiesis. The B12 level in the serum was undetectable. The infant’s lethargy resolved within 48 hours of intramuscular B12 injection, followed by rapid improvement of pancytopenia. The asymptomatic mother had a normal hemoglobin and mean corpuscular volume, but undetectable B12 level and positive antibodies to intrinsic factor, consistent with pernicious anemia masked by folate supplementation in the mother but causing symptoms in her infant.
Departments of *Pediatrics
†Pathology, Icahn School of Medicine at Mount Sinai, New York, NY
A.A.B.-S., C.-S.L., and B.W.: cared for the patient during admission and equally contributed to the manuscript. J.T.-F.: analyzed the original pathology and provided the images for the manuscript.
The authors declare no conflict of interest.
Reprints: Birte Wistinghausen, MD, Department of Pediatrics, Jack Martin Division of Pediatric Hematology-Oncology, Icahn School of Medicine at Mount Sinai, 1 Gustave-L-Levy Place, P.O. Box 1208, New York, NY 10029 (e-mail: email@example.com).
Received September 20, 2017
Accepted March 28, 2018