PedAM
Pediatric Disease Annotations & Medicines
| Disease | malabsorption syndrome |
| Phenotype | C0017154|chronic atrophic gastritis |
| Sentences | 1 |
| PubMedID- 20505848 | Although pa and scd share the common etiology, type a (autoimmune) chronic atrophic gastritis, with vitamin b12 malabsorption, they have distinct pathophysiologies.18,201 in the methionine cycle, folate- and vitamin b12-dependent ms catalyzes hcy methylation to met, as ch3-thf, serving as the methyl group donor, is demethylated to thf.47,52,58,151,200 impairment of this reaction causes defective dna synthesis, leading to megaloblastic, macrocytic anemia (ie, pa).21,58 supplemental folic acid can override the impairment, restoring dna synthesis and normalizing erythropoiesis.58,401 furthermore, in the methionine cycle, met is adenosylated to sam, which is demethylated to sah, which is deadenosylated to hcy.58 impairment of sam demethylation to sah impedes methylation reactions, leading to vacuolar demyelination, axonal degeneration, and neuronal death (ie, scd).21,58 supplemental folic acid cannot override the methylation impairment, resulting in progressive neuropathology and neuronal death.58 treating a combined folate and b12 deficiency with folic acid alone may correct hematological abnormalities, but not neurological abnormalities, and can aggressively worsen b12-deficient neurological sequelae.7,18,19,23,200,203,355 thus, b12 deficiency should be ruled out before correcting folate deficiency. |
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