USMLE Forum Archives - USMLE Step 2 CK - Hematology
Hematology
TheOne - 09-14-06 18:01
Anemias Due to Nutritional Deficiency
Megaloblastic
Anemia
Clinical Presentation
May occur in patients with either a folic acid or a B12 deficiency. Folic acid deficiency may develop within a few months following diminished intake (common in alcoholics), malabsorption, or increased utilization (pregnancy hemolytic anemia).There are also a number of drugs that may interfere with folate metabolism, e.g., ethanol, trimethoprim, pyrimethamine, methotrexate, and sulfasalazine. Patients with B12 deficiency may have diminished vibratory and positional sensation, ataxia, paresthesias and dementia.
Vitamin B12 deficiency takes years to develop because of the large bodily stores. Causes of B12 deficiency include:
Pernicious anemia
Gastrectomy
Pancreatic insufficiency
Small bowel bacterial overgrowth
Diseases of the ileum or ileal resection
Parasitic infestations (e.g., Diphyllobothrium)
Diagnosis
The MCV is increased and there may be leukopenia and thrombocytopenia as well as anemia since all cell lines require folate and B12. Hypersegmented neutrophils with more than five nuclear lobes is extremely suggestive.Vitamin B12 or folate levels are measured.A red blood cell folate may be a more accurate indicator than serum folate of the total body folate.A Schilling test is useful in determining the etiology of the B12 deficiency.
Therapy
Replace the deficient vitamin. Folic acid is usually given as 1mg daily; high doses, i.e., 5mg per day, may be used for patients with malabsorption.Vitamin B12 deficiency is corrected by giving 1mg of IM vitamin B12 daily for at least one week and then weekly until there is correction of the blood count.
TheOne - 09-14-06 18:01
Anemias Due to Nutritional Deficiency
Megaloblastic
Anemia
Clinical Presentation
May occur in patients with either a folic acid or a B12 deficiency. Folic acid deficiency may develop within a few months following diminished intake (common in alcoholics), malabsorption, or increased utilization (pregnancy hemolytic anemia).There are also a number of drugs that may interfere with folate metabolism, e.g., ethanol, trimethoprim, pyrimethamine, methotrexate, and sulfasalazine. Patients with B12 deficiency may have diminished vibratory and positional sensation, ataxia, paresthesias and dementia.
Vitamin B12 deficiency takes years to develop because of the large bodily stores. Causes of B12 deficiency include:
Pernicious anemia
Gastrectomy
Pancreatic insufficiency
Small bowel bacterial overgrowth
Diseases of the ileum or ileal resection
Parasitic infestations (e.g., Diphyllobothrium)
Diagnosis
The MCV is increased and there may be leukopenia and thrombocytopenia as well as anemia since all cell lines require folate and B12. Hypersegmented neutrophils with more than five nuclear lobes is extremely suggestive.Vitamin B12 or folate levels are measured.A red blood cell folate may be a more accurate indicator than serum folate of the total body folate.A Schilling test is useful in determining the etiology of the B12 deficiency.
Therapy
Replace the deficient vitamin. Folic acid is usually given as 1mg daily; high doses, i.e., 5mg per day, may be used for patients with malabsorption.Vitamin B12 deficiency is corrected by giving 1mg of IM vitamin B12 daily for at least one week and then weekly until there is correction of the blood count.
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#2
Re: Hematology
TheOne - 09-16-06 13:58 You're welcome my Friend,
Diseases of Bone Marrow Failure
Aplastic Anemia
Clinical Presentation
This is an acquired disorder of the bone marrow stem cells, which results in anemia, leukopenia, and thrombocytopema. Most cases are idiopathic, but a minority are associated with viral illness (hepatitis, mononucleosis, CMV), and some with medications (sulfonamides, chloramphenicol. D-penicillamine). Patients will present with symptoms of anemia or thrombocvtopenia and less commonly with leukopenia-associated fevers.
Diagnosis
MCV is normal and the peripheral smear is unremarkable.A bone marrow biopsy is necessary and will distinguish aplastic anemia from myelodysplastic syndrome, leukemia, or tumor infiltration.
Treatment
Obviously discontinue any offending drugs. In young patients. a bone marrow transplant may be curative. Patients who are not candidates for bone marrow transplant may be treated with immunosuppressants (cyclosporine or antilymphocyte globulin).Trv to keep packed red blood cell transfusions to a minimum and give prophylactic platelet transfusion only to patients with a platelet count of less than 10,000. Patients with fever and neutropenia must be treated with empiric broad-spectrum antibiotics.
#3
Re: Hematology TheOne - 09-18-06 17:10 Myelodysplastic Syndrome
Clinical Presentation
A collection of acquired clonal disorders of stem cells that are classitied based on morphologic findings on the peripheral smear and bone marrow.The syndromes may be idiopathic or develop secondary to radiation or chemotherapy. Presentations may be related to symptoms of pancytopenia.These patients may progress to complete marrow failure or acute leukemia.
Sideroblastic anemia is characterized by an inability to in corporate iron into the heme molecule and deposition of a ring into the RBC. Acquired sideroblastic anemia may occur in response to various drugs, e.g.. isoniazid, chloramphenicol. and especially alcohol.
Diagnosis
MCV is usually normal, but may be low in patients with sideroblastic anemia. Sideroblastic anemia can be distinguished from iron-deficiency anemia since in sideroblastic anemia the iron and transferrin are normal or elevated. Diagnosis is established by demonstrating abnormal cells on bone marrow.
Treatment
Supportive with transfusion as necessary. Erythropoietin given subcutaneously three times a week may be useful in diminishing dependence on red cell transfusion. Pvridoxine is commonly used as a supplement in patients treated with INH and may reduce the likelihood of sideroblastic anemia.
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