The CSF<unk>  level is usually undetectable at the time of diagnosis. Even when the blood<unk>  level is corrected, or far above normal, the CSF<unk>  level remains low, consistent with impaired transport across the choroid plexus. The normal CSF<unk>  level in children over the first three years of life is in the 75 to 150 nM range. In subjects with HFM it is very difficult indeed, rarely possible, to bring the CSF<unk>  level into the normal range even with substantial doses of parenteral<unk>  Differential diagnosis HFM must be distinguished from cerebral<unk>  deficiency (CFD)– a syndrome in which there is normal intestinal<unk>  absorption, without systemic<unk>  deficiency, but a decrease in CSF<unk>  levels. This can accompany a variety of disorders. One form of CFD is due to loss-of-mutations in<unk>  receptor-α, (FRα), which transports<unk> s via an endocytic process. While PCFT is expressed primarily at the basolateral membrane of the choroid plexus, FRα is expressed primarily at the apical brush-border membrane. Unlike subjects with HFM, patients with CFD present with neurological signs a few years after birth. The basis for the delay in the appearance of clinical manifestations due to loss of FRα function is not clear; the normal blood<unk>  levels may be protective, although for a limited time.
Hereditary folate malabsorption
Cerebral folate deficiency
Folate deficiency
Iron metabolism disorder
Iron deficiency
Zinc deficiency
Vitamin E deficiency
Familial isolated vitamin E deficiency