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Key words: cobalamin deficiency; juvenile megaloblastic anaemia; megaloblastic anaemia 1; pancytopenia; selective vitamin B12 malabsorption with proteinuria; vitamin B12 deficiency. CaseA 2-year-old girl of Mexican and Spanish descent came to our hospital with her mother for 2 weeks of pallor and fatigue. She was born full term to parents who were first cousins. Past medical history was unremarkable, and development was appropriate. Diet was balanced and unrestricted. Growth parameters were appropriate. She appeared well nourished but with obvious pallor. Liver and spleen were not palpable. Neurologic examination was unremarkable.Laboratory tests revealed pancytopenia with white blood cell count of 2.9 × 10 3 /μL, haemoglobin of 4.8 g/dL, platelets of 98 × 10 3 /μL, mean corpuscular volume of 94 fL and red cell distribution width of 43%. Additional serum tests showed lactate dehydrogenase of 3128 U/L (normal 90-220), total bilirubin 1.2 mg/dL (normal 0-1) and direct bilirubin 0.3 mg/dL (normal 0-0.3). On review of the peripheral blood smear, macrocytosis and hypersegmented neutrophils were seen. The differential diagnosis of macrocytosis in infants and children is shown in Table 1.The finding of megaloblastic anaemia, defined by hypersegmented neutrophils in the peripheral blood, raised concern for a problem with deoxyribonucleic acid (DNA) synthesis during red blood cell production. Therefore, serum levels of vitamin B 12 (cobalamin) and folate were obtained. Vitamin B12 was 45 pg/mL (normal 211-911), and folate was 14 ng/mL. Urine dipstick showed 30 mg/dL protein.DNA mutation analysis revealed a homozygous mutation of the amnionless gene (AMN) consistent with Imerslund-Gräsbeck syndrome (IGS, megaloblastic anaemia 1; OMIM #261100). Our patient was treated with intramuscular vitamin B12 injections. At a clinic visit 2 months later, serum vitamin B12 level was 384 pg/mL. The patient is now a healthy and thriving 6-year-old girl. She continues to have mild proteinuria (30-100 mg/dL) without evidence of impaired glomerular function. DiscussionVitamin B12 (cobalamin), a water-soluble vitamin, is needed as a cofactor for two reactions in humans. Methylcobalamin is a cofactor for the cytoplasmic enzyme, methionine synthase (EC 2.1.1.13), while adenosylcobalamin is a cofactor for the mitochondrial enzyme, methylmalonyl CoA mutase (EC 5.4.99.2). Cobalamin is involved in DNA synthesis, haematopoiesis and myelination.Since humans or plants cannot synthesise vitamin B12, it needs to be ingested in the diet from animal foods such as meat, poultry, shellfish, eggs and milk. After ingestion, B12 is bound to R-protein, also known as haptocorrin, which is present in the saliva. The action of pancreatic enzymes and the change in pH in the small intestine releases cobalamin from R-protein. In the stomach, parietal cells produce intrinsic factor (IF), which binds vitamin B12 that has been released from R-protein. This vitamin B12-IF complex then attaches to the cubam receptor, a complex composed of cubulin and amnionless, in the ...

A 14-year-old male presented to the hospital after syn cope during football practice on a hot summer day. On examination, temperature was 40.41C (104.71F) and heart rate was 180 beats per minute. He was unresponsive, intubated, and cooled in the pediatric intensive care unit. Laboratory values revealed acute kidney injury and ischemic hepatitis. Complete blood count showed a white blood cell count of 17 Â 10 9 /L, hemoglobin of 14.8 g/L, platelet count of 395Â10 9 /L, and mean corpuscular volume of 83.8 fL (normal, 81.4 to 91.9 fL). Peripheral blood smear showed hypersegmented neutrophils with "botryoid" nuclei (Supplemental Fig. 1 Supplemental Digital Content 1, http://links.lww.com/JPHO/A98).Hypersegmented neutrophils are classically seen with folate (vitamin B 9 ) orcobalamin (vitamin B 12 ) deficiency. These morphologic changes of the neutrophil nucleus occur due to impaired DNA synthesis from inadequate substrate or impaired replication from a toxin or medication effect. Arrest of nuclear maturation, impaired cell division, and unbalanced cell growth results in characteristic large cells with immature nuclei with relative cytoplasmic maturity. Red blood cell macrocytosis often accompanies hypersegmented neutrophils and can be seen in hypothyroidism, alcohol abuse, uremia, and myelodysplastic syndromes.Hypersegmented neutrophils without red blood cell macrocytosis, as in our patient, has been described in patients with hyperthermia, uremia, and concurrent megaloblastic and microcytic anemia from combined folate and/ or cobalamin deficiency along with iron deficiency or thalassemia. As the finding of hypersegmented neutrophils preceeds macrocytosis, neutrophil hypersegmentation without macrocytosismay represent early cobalamin and folate deficiency. 1 The term "botryoid" refers to nuclei that appear like a cluster of grapes around a stem. 2 Botryoid nuclei have been described in patients with hyperthermia due to cocaine and methamphetamine use, 3 malignant hyperthermia, neuroleptic malignant syndrome, 4 and autoimmune disorders such as rheumatoid arthritis, psoriatic arthritis, and systemic sclerosis. 5 In comparison, the multilobed nuclei in cobalamin and folate deficiency appear disorganized.The pathogenesis of botryoid nuclei in hyperthermia has not been clearly elucidated. Hyperthermia may activate the intrinsic signaling pathway that initiates apoptosis since pyknosis, nuclear condensation in the setting of irreversible cell death, is seen in neutrophils in response to hyperthermia. 6 In addition, microtubular decomposition may play a role. 7 In vitro experiments have shown that radially segmented neutrophils are induced by applying heat. 8 Botryoid changes in >50% of neutrophils on a peripheral blood smear may be sufficient to diagnose heatstroke. 2 Fewer than 50% botryoid neutrophils is suggestive of heatstroke. Clinicians should be aware that hyperthermia can cause hypersegmented neutrophils so as to avoid unnecessary evaluations for other etiologies.Our patient's mental status and renal function impro...