WBR0963
| Author | [[PageAuthor::Mugilan Poongkunran M.B.B.S [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 3 |
| Main Category | MainCategory::Primary Care Office |
| Sub Category | SubCategory::Hematology |
| Prompt | [[Prompt::A 66 year old female presents to the office with a 1 month history of fatigue and weakness. On further review of history, she says she has been feeling very weak even to do minor household work. She denies any change in appetite or weight. She attained menopause at the age of 54 and is not taking any estrogen pills. Her past history is significant for carcinoma breast and is on chemotherapy for the past 1 year. Her family history is unremarkable. She does not smoke and drink. Her vitals are temperature: 36.7 C, blood pressure: 120/80 mmHg, pulse: 102/min and respiration: 16/min. All system examinations are normal except pallor. Her laboratory values are :
Hb : 7 g/dl RBC’s : 2 million/cmm WBC’s : 6000/cmm Platelets : 300,000/ cmm Segmented neutrophils : 68 % Bands : 2 % Eosinophils : 2 % Lymphocytes : 32 % Monocytes : 6 % MCHC : 34 % MCV : 115 fl Which of the following is the most appropriate treatment in this patient ?]] |
| Answer A | AnswerA::Vitamin B12 |
| Answer A Explanation | AnswerAExp::''' Incorrect ''' : Vitamin B12 is used to treat megaloblastic anemia caused by its deficiency. |
| Answer B | AnswerB::Folic acid |
| Answer B Explanation | AnswerBExp::''' Incorrect ''' : Folic acid is used to treat megaloblastic anemia caused by its deficiency. |
| Answer C | AnswerC::Ferrous sulphate |
| Answer C Explanation | [[AnswerCExp:: Incorrect : Ferrous sulphate is used in iron deficiency anemia.]] |
| Answer D | AnswerD::Folinic acid |
| Answer D Explanation | [[AnswerDExp:: Correct : Folinic acid is administered at the appropriate time following methotrexate as part of a total chemotherapeutic plan, where it may "rescue" bone marrow and gastrointestinal mucosa cells from methotrexate.]] |
| Answer E | AnswerE::Intrinsic factor |
| Answer E Explanation | AnswerEExp::''' Incorrect ''' : Intrinsic factor is used to treat megaloblastic anemia caused by its deficiency. |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::Megaloblastic anemia can be due to vitamin B12 deficiency, folic acid deficiency or intrinsic factor deficiency. Patient on chemotherapeutic agents such as methotrexate develop anemia due to dihydrofolate reductase inhibition and cannot be corrected by folic acid, but by folinic acid. Folinic acid is a 5-formyl derivative of tetrahydrofolic acid. It is readily converted to other reduced folic acid derivatives (e.g. tetrahydrofolate), and thus has vitamin activity which is equivalent to folic acid. However, since it does not require the action of dihydrofolate reductase for its conversion, its function as a vitamin is unaffected by inhibition of this enzyme by drugs such as methotrexate. Folinic acid is administered at the appropriate time following methotrexate as part of a total chemotherapeutic plan, where it may "rescue" bone marrow and gastrointestinal mucosa cells from methotrexate. There is no apparent effect on preexisting methotrexate-induced nephrotoxicity. Folinic acid is also used in combination with the chemotherapy agent 5-fluorouracil in treating colon cancer. In this case, folinic acid is not used for "rescue" purposes; rather, it enhances the effect of 5-fluorouracil on inhibiting thymidylate synthase. Folinic acid is also sometimes used to prevent toxic effects of high doses of antimicrobial dihydrofolate reductase inhibitors such as trimethoprim and pyrimethamine. Educational Objective: |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Megaloblastic anemia |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |