Optimal vitamin B
12 status during infancy is important for many aspects of child health, growth and development. Infants are dependent on the mother for vitamin B
12 during pregnancy and while breastfeeding. B
12 is transmitted from the mother to the infant especially through the transplacental route and stored in sufficient quantities to meet the needs of the child during the first 12 months. The symptoms of deficiency are therefore usually not seen in the initial 6 - 12 months of life in a healthy child; therefore, deficiency in the first 6 - 12 months only occurs in infants with maternal vitamin B
12 deficiency (
1,
13,
14). B
12 deficiency not treated during pregnancy can lead to growth retardation, hypotonia, important neurological and functional losses in infants, and the symptoms can be permanent if only detected at a late stage (
15).
Prevention of common vitamin deficiencies in the first two years of age is an important priority for developing countries. The relatively low concentrations of plasma vitamin B
12 in younger infants identified by this study may be due to low maternal intake of vitamin B
12 rich foods during pregnancy and lactation. Cultural beliefs and food taboos restrict intake of foods that are rich in vitamin B
12 during pregnancy and breastfeeding, and low consumption of meat, fish and other animal source foods may also cause poor maternal nutritional status during pregnancy and breastfeeding. Furthermore, the relatively low coverage of vitamin B
12 supplementation in younger children (6 to 12 months) may also contribute to the low concentrations of plasma vitamin B
12 reported in this population (
16).
Some studies suggest that vitamin B
12 deficiency and marginal deficiency are highly prevalent worldwide and vitamin B
12 deficiency is also of public health concern. Vitamin B
12 deficiency may be more prevalent in vegetarians, vegans, and people living in low-income communities where they may have limited purchasing power to acquire animal food sources or may not have access to fortified foods or supplements (
17,
18). Koc et al. found B
12 deficiency in 41% of newborns in the Southeastern Anatolia Region of Turkey where B
12 deficiency is common (
5). They emphasized that detecting B
12 deficiency and its early treatment in the regions where the socioeconomic level is low is important to prevent any developmental sequelae that could develop in the baby. Vitamin deficiency during pregnancy in the mother has similarly been reported to affect the infant starting in the intrauterine period in many studies (
19,
20).
Although there is no complete consensus regarding the normal cut-off level of vitamin B
12, we accepted < 200 pg/mL as the cut-off in laboratory evaluations (
21). We found vitamin B
12 deficiency in 163 (53%) mothers of the 303 patients who were diagnosed with B
12 deficiency under the age of two years. The most important characteristics in the group with low B
12 level in both the mother and infant was the low birth weight of the infants (P = 0.001). Similar results are reported in different studies because the B
12 deficiency of the mother during pregnancy may lead to many metabolic and neurological problems starting with the intrauterine period and especially low birth weight in the newborn (
22,
23).
The vitamin B
12 levels in breast milk and the mother are parallel in the lactation period and sufficient B
12 cannot be obtained from breast milk (the most important B
12 source of the infant) when the mother has B
12 deficiency (
24). We found that 274 children had received breast milk regularly during the first 3 - 6 months; breastfeeding was not regular and formula was started early in the other 27 patients. We found a high rate (91%) of breastfeeding in the group with low vitamin B
12 levels in both the mother and the child in our study (P = 0.058). The deficiency in the mother affects the baby during the intrauterine period at the first stage and complicated clinical pictures can be encountered if the deficiency is not treated during the breast feeding period.
The cells that are mostly affected by vitamin B
12 deficiency are the central nervous system cells with rapid mitotic activity. The clinical findings include lethargy, apathy, hypotonia, tremor, and convulsions. In individuals with B
12 deficiency, methylmalonyl-CoA accumulates and is used in the synthesis of fatty acids instead of acetyl-CoA. This results in unstable myelin that degrades more easily and negatively affects the brain development and cognitive performance of growing children (
25).
The exact mechanism underlying neurological deficits in Vitamin B
12 deficiency is not clearly understood. However, vitamin B
12 deficiency is thought to cause imbalance between the growth factors influencing the central nervous system and neurotoxic cytokines, and increased lactate, glutamate and excitatory amino acids (
26-
28). Therefore, epilepsy is triggered and EEG abnormalities are manifestations of vitamin B
12 deficiency in pediatric patients. Several studies currently exist describing an association between vitamin B
12 deficiency and EEG abnormalities and epilepsy (
29-
34). We encountered central nervous system signs and symptoms especially in rapidly growing infants in the early period between 2 and 18 months. A remarkable finding was the simultaneous low levels of vitamin B
12 in the mother in 55 of the 69 children who presented with neurological symptoms (P < 0.05). The presenting signs and symptoms of these 55 patients were seizure, hypotonia, and macrocephaly. The type, severity and duration of involuntary movements related to vitamin B
12 deficiency varies considerably. In this study seizures types were generalized tonic clonic, generalized tonic and simple partial. EEG evaluations of the 30 infants revealed generalized epileptic activity in 9 and focal activity in 3. Atrophy of corpus callosum, retardation in myelination, demyelination areas and ventricular dilatation findings were seen on the MR images. Cortical atrophy, hypoplasia of the corpus callosum, delayed myelination, and ventricular dilatation are the most common neuroradiological findings in the literature (
3,
30,
31,
34). Patients only presented with macrocephaly, irritability and tremor and we did not observe any seizure in the group where B
12 levels of mothers were normal. MR findings were mostly normal apart from ventricular dilatation and demyelination. Neurologic findings were more severe and complex in the group where B
12 levels were low both in the mother and infant rather than the group where B
12 levels normal in mother. The fact that neurological symptoms can be detected before the emergence of megaloblastic anemia symptoms is critical for clinicians. The rate of presentation with neurologic findings but without anemia was high in studies conducted on adults. Anemia may not be a presenting symptom or its rate can be lower than other symptoms (
2,
9,
35). However, the most common symptom in this study was anemia (62.4%) followed by neurological findings (22.8%). Although there is no clear consensus regarding the treatment of vitamin B
12 deficiency, we administered vitamin B
12 parenterally to our patients as recommended. The dose was 100 µg per day for 7 days, 100 µg per week for 4 weeks, and then 100 µg per month for 3 months (
1,
36). The mothers were also prescribed vitamin B
12 parenterally. The head circumference of 3 of the 7 patients that had presented with macrocephaly was within the normal percentile range during follow-up. Those who showed the fastest response to vitamin B
12 treatment were the hypotonia and tremor patients. The seizures did not recur, and the antiepileptic drugs were discontinued during the follow-up with vitamin B
12 treatment in patients who had experienced a generalized tonic clonic seizure. No other complications were observed during a median follow-up duration of 1 year (6 months to 2.5 years).
Detecting B12 deficiency and starting treatment early is important for preventing irreversible symptoms. B12 deficiency in mothers particularly is a risk factor in infants developing neurologic symptoms, thus mothers should be checked after delivery and during lactation as well as their infants. Nutritional deficiency patients can present with confusing signs and symptoms such as macrocephaly or microcephaly, hypotonia, tremor, irritability, and seizure that can make things difficult for the clinicians and require further investigations for the differential diagnosis. Physicians should be aware that attempts to solve the problem should start during pregnancy, and a social consciousness needs to be developed to prevent B12 deficiency. It is known that irreversible complications can develop if the diagnosis and treatment of B12 deficiency are delayed. Early screening of blood vitamin B12 levels will obviously improve the health of mother and child and make things easier for clinicians.