| Inherited disorders of folate transport and metabolism 3: |
| Definite |
| Methylene-H4 folate reductase deficiency |
| Functional methyltetrahydrofolate (methyl-H4 folate): |
| homocysteine methyltransferase (methionine synthase) deficiency caused by cobalamin E (cblE) or G(cblG) disease |
| Glutamate formiminotransferase deficiency |
| Hereditary folate malabsorption |
| Putative |
| Dihydrofolate reductase deficiency |
| Methenyl-H4 folate cyclohydrolase deficiency |
| Cellular uptake defects |
| Primary methyl-H4 folate:homocysteine methyltransferase deficiency |
|
| Nervous system clinical features37: |
| (a). Neonatal and early infancy (<3 months): |
| Poor feeding |
| Lethargy |
| Hypotonia/hypertonia |
| Seizures |
| Coma |
| (b) Late infancy and early childhood (>3 months–<10 years): |
| Slow development |
| Lethargy |
| Mental deterioration |
| Encephalopathy |
| Seizures |
| Spastic paresis (subacute combined degeneration) |
| Extrapyramidal signs |
| Neuropathy |
| (c) Late childhood and early adulthood (>10 years): |
| Previous mild retardation |
| Mental deterioration |
| Behaviour disturbance |
| Encephalopathy |
| Myelopathy (subacute combined degeneration) |
| Neuropathy |