pack Flashcards
(17 cards)
What causes megaloblastic anemia?
Impaired DNA synthesis, which causes decreased production of rapidly dividing cells
What are the tissues that will first be effected by the impairment of dna synthesis?
Rapidly dividing cells
What are the three major causes of b12 and folate deficiency?
inadequate intake, increased need, impaired absorption.
What is the difference between megaloblastic anemia and macrocytic anemia?
Megloblastic anemia is a type of macrocytic anemia
that is caused by a deficiency in b12/folate.
What does a lack of b12 cause in relation to serum levels?
elevated serum levels of methylmalanic acid
(So if the question mentions an elevated level of MMA you immediately know that it is a B12 deficiency)
What is the role of b12?
It transfers a methyl group from 5-methyltetrahydrofolate (5-methyl THF) to homocysteine, creating methionine.
What is the role of folic acid?
required to transfer carbon units - methyl group - from donors to receivers.
In what form does folate circulate in the blood?
Circulates as as 5-methyl THF (inactive form).
How is 5 methyltetrahydrofolate converted to tetrahydrofolate?
What does the b12 do with the methyl?
1.B12 takes the methyl group from 5-Methyl THF turning it into THF.
.
2.B12 uses that methyl group on Homocystine converting to Methionine.
How is THF converted to 5,10-methyl tetrahydrofolate?
It is converted using serine which turns into glycine.
What is the role of 5,10-methyltetrahydrofolate in the making of the thymine.
A methyl group is taken from 5,10-methyl THF and put onto dUMP (uracil), converting into dTMP. (Thymine)
What happens to dna synthesis when you have vitamin b12 and/or folate deficiency?
There will be no thymine, causing uracil to be substituted in its place, but DNA polymerase will Deattach the uracil causing a gap in the dna, causing dna replication to stop.
What is the result of DNA fragmentation?
.
What type of cells does this mainly effect?
.
Where are those cells normally located?
DNA is non-functional and cell division stops. Resulting in apoptosis in erythroid progenitors and precursors, which are normally found in the bone marrow.
What happens when the erythroid progenitors and precursors escape cell apoptosis?
are useless and larger than normal.
What happens to neutrophils in megaloblastic anemia?
Neutrophils show hyper-segmented nuclei
(with six or more lobes).
What are some of the symptoms of megaloblastic anemia?
fatigue, weakness, and shortness of breath
.
.
Loss of epithelium along the gastrointestinal tract causes gastritis
nausea, or constipation.
What are some of the lab findings?
In blood:MCV is high
Reticulocyte count is low
Neutrophils are hypersegmented
In bone marrow: hypercellular and the
erythroblasts are large
