Megaloblastic Anemias презентация

Megaloblastic Anemias

PLAN

Definition: Macrocytic Anemia MCV>100fL Impaired DNA formation due to lack of: B12 or folate in ultimately active form use of antimetabolite drugs Macrocytosis also caused by Liver disease with inadequate cholesterol esterification Alcohol abuse independent of folate (MCV 100-105) Myelodysplasia Post-splenectomy HIV drugs Dilantin

Vitamin B12: Cobalamin Meat and dairy products only Typical American diet contains 5-7mcg/d Minimum daily requirement 6-9 mcg/d Total body store 2-5 mg (half in liver) Helps to synthesize thiamine, thus deficiency leads to problems with DNA replication

B12: Cobalamin absorption Initially bound to protein in diet, liberated by acid and pepsin, then binds to R factors in saliva and gastric acids Freed from R factors by pancreatic proteases them binds to Intrinsic Factor secreted by gastric parietal cells Absorbed together (Cbl + IF) in ileum Released from IF in ileal cell then exocytosed bound to trans-Cbl II Cbl bound to transcobalamin II binds to cell surface receptors and is endocytosed

Causes of B12 Deficiency: Pernicious Anemia Autoantibody to Intrinsic Factor detectable in <70% Highly specific, but insensitive 2 types of anti-IF antibody Blocks attachment of Cbl to IF Blocks attachment of Cbl-IF complex to ileal receptors Chronic atrophic gastritis Autoantibody against parietal cells (H-K-ATPase) though pathology indicates destruction by CD4+ T cells Increased risk of gastric cancer (carcinoid and intestinal- type)

Causes of B12 Deficiency: Growing Older Usually mild and subclinical Age >65 approx 5% Age >75 approx 10%+, up to 40% in institutionalized patients Unclear mechanism gastric atrophy inadequate intake Achlorhydria

Causes of B12 Deficiency: Surgery, Medication, Worms, Etc. Gastrectomy/Bariatric surgery Ileal resection or bypass Ileal disease (TB, lymphoma, amyloid, post-radiation, Crohn’s) Enteropathies (protein losing, chronic diarrhea, celiac sprue Fish tapeworm (Diphyllobothrium latum) infection Bacterial overgrowth HIV infection Chronic alcoholism Sjogren’s syndrome Pancreatic Exocrine Insufficiency Strict vegan diet Inherited Trans-Cbl II or IF deficiency decreased uptake of IF-Cbl (Imerslun-Grasbeck’s or juvenile megaloblastic anemia) - also presents with proteinuria Homocysteinuria, severe abnormalities of methionone synthesis, abnormal lysosomal exporter Decreased absorption from medication Neomycin Metformin (biguanides) up to 10-25% PPI Nitric oxide (inhibits methionine synthase)

B12 Deficiency Symptoms Atrophic glossitis (shiny tongue) Shuffling broad gait Anemia and related sx Vaginal atrophy Malabsorption Jaundice Personality changes Hyperhomocysteinemia Neurologic symptoms (next slide) Copper deficiency can cause similar neurologic symptoms

B12 Symptoms: Neurologic Paresthesias Memory loss Numbness Weakness Loss of dexterity due to loss of vibration and position sense Symmetric neuropathy legs>arms Severe weakness, spasticity, clonus, paraplegia and incontinence

Subacute Combined Degeneration Degeneration and demyelination of the dorsal (posterior) and lateral spinal columns

B12 Lab findings Macroovalocytic anemia with elevated serum bili and LDH Increased red cell breakdown due to ineffective hematopoiesis Retic, WBC & platelets normal to low Hypersegmented neurophils Also occur in renal failure, fe deficiency, inherited

Bone Marrow Hypercellular marrow Megaloblastic erythroid hyperplasia Giant metamyelocytes Due to slowing of DNA synthesis and delayed nuclear maturation Methionine deficiency may play a central role

Folate Animal products (liver), yeast and leafy vegetables Normal requirement 400mcg/day Pregnancy/Lactation: 500-800mcg/day Increased requirement in hemolytic anemia and exfoliateive skin disease Body stores: 5-10mg

Folate Metabolism Binds to folate receptor, becomes polyglutamated intracellularly Many drugs (trimethoprim, methotrexate, pyrimethamine) inhibit dihydrofolate reductase

Causes of Folate Deficiency Malnutrition: Destroyed by heat during cooking Alcoholism (decreased in 2-4 days): impairs enterohepatic cycle and inhibits absorption Increased requirement in hemolytic anemia, pregnancy, exfoliative skin disease IBD, celiac sprue Drugs Trimethoprim, Methotrexate, Primethamine (inhib DHFR) Phenytoin: blocks FA absorption, increases utilization (mech unknown)

Folate deficiency symptoms Similar symptoms as B12 save for neurologic symptoms Presentation is different classically: Alcoholic Very poor dietary intake Older Depressed Living alone

Whom should you test for B12 or Folate deficiency? MCV >100 with or without anemia Hypersegmented neutrophils Pancytopenia of uncertain cause Unexplained neurologic s/sx Alcoholics Malnourished, particularly the elderly Vegans if no hx of supplementation Diabetics on metformin with new onset neuropathy

Lab testing for diagnosis

Shilling Test 1. PART 1: Oral labeled B12 and IM unlabeled B12 at the same time to saturate tissue stores 2. 24h urine to assess absorption >5% normal <5% impaired 3. PART 2: Repeat w/oral IF if now normal =PA if abnormal = malabsorption 4. Can continue with antibiotics to look for bacterial overgrowth, pancreatic enzymes for exocrine insufficiency

B12 Deficiency: Treatment IM B12 1000mcg daily x 1 wk then 1000mcg weekly x 1 month Then 1000mcg monthly for life for PA Oral high dose 1-2 mg daily As effective but less reliable than IM Currently only recommended after full parenteral repletion Sublingual, nasal spray and gel formulations available

Vegan B12 Recommendations Daily multivitamin with10mcg/d Available in a few specific commercial nutritional yeasts most of which contain B12 from Pseudomonas sp., Propionibacterium sp. or Streptomyces sp.  Red Star Vegetarian Support Formula  Twinlab Natural Nutritional Yeast Probiotics are NOT sufficient to provide adequate B12 Keep supplements in the fridge and out of light Encourage supplement for prenatal counseling of vegan or ovo-lacto vegetarian women (prenatal vitamin is sufficient unless deficient) B12: Are You Getting It? By Jack Norris, RD VeganHealth.org

Folate Deficiency Treatment Oral folate 1mg daily for 4 months or until hematologic recovery Rule out B12 deficiency prior to treament as folic acid will not prevent progression of neurologic manifestations of B12 deficiency Repeat testing for B12 deficiency may be reasonable for those on long-term folic acid therapy if hematologic (macrocytosis or ↑LDH) or neurologic sx persist

Summary Deficiency of folate or B12 Macrocytic anemias; with or with out other cytopenias Slowly developing anemia, usually well compensated Response to therapy rapid and dramatic Treatment necessary to avoid other complications Anemia is secondary to other disease process

References Carmel, R. Prevalence of undiagnosed pernicious anemia in the elderly. Arch Intern Med 1996; 156:1097 Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 2000. Hvas, AM, J Ellegaard and A Nex. Vitamin B12 Treatment Normalizes Metabolic Markers But Has Limited Clinical Effect: A Randomized Placebo-controlled Study. Clinical Chemistry 47:8.1396–1404 (2001) Kaptan, K, C Beyan, AU Ural et al. Helicobacter pylori –Is it a novel causative agent in Vitamin B12 deficiency? Arch Intern Med 2000; 160:1349 Norris, Jack. B12: Are You Getting It? Vegan Outreach. Available online: http://www.veganhealth.org/b12, Accessed October 26, 2009 Schrier, S. Etiology and clinical manifestaqtions of vitamin B12 and folic acid deficiency. Up to date. Version 17.2. Accessed October 26, 2009. Schrier, S. Diagnosis and treatment of vitamin B12 and folic acid deficiency. Up to date. Version 17.2 Accessed October 26, 2009.