BY DR. Hayam Hebah Associate Professor of Internal Medicine AL Maarefa College

Objectives: Background Causes B12 Folic acid Management.

BACKGROUND: Megaloblastosis describes a heterogeneous group of disorders that share common morphologic characteristics: large cells with an arrest in nuclear maturation. Nuclear maturation is immature relative to cytoplasmic maturity. Cells seen in bone marrow aspirates and in peripheral smears have been called megaloblasts. Megaloblastic changes are most apparent in rapidly dividing cells such as blood cells and gastrointestinal cells.

PATHOPHYSIOLOGY: The common feature in megaloblastosis is a defect in DNA synthesis in rapidly dividing cells. To a lesser extent, RNA and protein synthesis are impaired. B12 helps to synthesize thiamine, thus deficiency leads to problems with DNA replication

Causes of Megaloblastic Anemia B12 deficiency Folate deficiency Pernicious anemia

OTHER CAUSES OF MEGALOBLASTOSIS: *Medications(antimetabolite drugs as azathioprine) *Direct interference of DNA synthesis by: -- HIV infections --myelodysplastic disorders. *Liver disease with inadequate cholesterol esterification *Alcohol abuse independent of folate (MCV ) *Post-splenectomy

8 VITAMIN B 12 AND FOLIC ACID-PHYSIOLOGIC CONSIDERATIONS Vitamin B 12 Folic acid Sources meat, fish green vegetables, yeast Daily requirement 2-5 ug ug Body stores 3-5 mg (liver) 10-12mg (liver) Places of absorption ileum duodenum and proxymal segment of small intestine

Vitamin B12 (cobalamin)

The primary sources of cobalamin (Clb), a cobalt- containing vitamin, are meat, fish, and dairy products and not vegetables and fruit. Cobalamin is the only water-soluble vitamin stored in the body. About 3 mg of cobalamin are stored, of which 1 mg is stored in the liver. Hence, it takes 3-5 years to develop a vitamin B-12 deficiency after a total gastrectomy. In contrast, significant amounts of folate are not stored. Clinical evidence of folate deficiency can occur within a month after folate intake is stopped

B12 Metabolism Bind to cobalophilin (cobalamine binding protein) in saliva and gastric secretion Bind to IF (from parietal cell) in the duodenum Cbl-IF complex bind to receptor (cubilin) at distal ileum for mucosal absorption 1% B12 can be absorbed without IF (megadose of B12 for IF deficiency )

14 MEGALOBLASTIC ANEMIAS Causes of Vit.B 12 deficiency(1) 1. Malabsorption a) Inadequate production of intrinsic factor - pernicious anemia (autoimmune destruction of gastric parietal cells) - gastrectomy, partial or total b) Inadequate releasing vit. B 12 from food - (partial gastrectomy, atrophic gastritis and achlorhydria (mainly in elderly patients), - chronic pancreatic insufficiency (the alkaline environment in the small intestine is insufficient for release of cobalamin from R-proteins and binding to intrinsic factor) c) Terminal ileum disease (sprue, celiac disease, ilea resection, Crohn disease, Imerslund syndrome)

(Causes of Vit.B 12 deficiency(2 d) Competition for intestinal B 12 : - bacterial overgrowth: jejunal diverticula, intestinal stasis and obstruction due to strictures, blind-loop syndrome - Fish tapeworm Diphyllobothrium latum, found in Canada, Alaska, and the Baltic Sea. 2-Inadequate intake Dietary cobalamin deficiency rarely causes megaloblastic anemia, except in vegetarians 3. Inadequate utilisation Drugs: PAS, Neomycin, Colchicin, Nitrous oxide

in the Zollinger-Ellison syndrome, the acid environment also prevents binding of cobalamin to intrinsic factor. Disorders of the terminal ileum can result in cobalamin deficiency. Because the terminal ileum is the site of uptake of cobalamin-IF complexes, tropical sprue, inflammatory bowel disease, lymphoma, and ileal resection can lead to cobalamin deficiency. Blind loop syndrome can result in cobalamin deficiency. Bacterial colonization can occur in intestines deformed by strictures, surgical blind loops, scleroderma, inflammatory bowel disease, or amyloidosis. Bacteria then compete with the host for cobalamin.

A partial list of medications that can cause cobalamin deficiency includes: 1. purine analogs (6-mercaptopurine, 6-thioguanine, acyclovir), 2. pyrimidine analogues (5-fluorouracil, 5-azacytidine, zidovudine), 3. ribonucleotide reductase inhibitors (hydroxyurea, cytarabine arabinoside) 4. drugs that affect cobalamin metabolism (p - aminosalicylic acid, phenformin, metformin).

Causes of B12 Deficiency 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 (juvenile megaloblastic anemia) - also presents with proteinuria Homocysteinuria, severe abnormalities of methionone synthesis, abnormal lysosomal exporter Decreased absorption from medication Neomycin Metformin up to 10-25% PPI Nitric oxide (inhibits methionine synthase)

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)

Folate is found in vegetables, fruits, and animal protein Physiological folate absorption and transport is receptor mediated. There is no equivalent of IF to stabilize and transport ingested folate. Uptake occurs in the jejunum and throughout the small intestine Storage is limited, and folate deficiency develops about 3-4 weeks after the cessation of folate intake The daily requirement for adults is about 0.4 mg/d.

Causes of folate deficiency: Low folate food content and overcooking are causes for folate deficiency, especially in elderly persons. Increased demand can result in deficiency as in hemolysis, pregnancy, lactation, rapid growth, hyperalimentation, renal dialysis, psoriasis, and exfoliative dermatitis. Intestinal disorders that impede folate absorption include tropical sprue, nontropical sprue (celiac disease or gluten sensitivity), amyloidosis, and inflammatory bowel disease.

Medications include: phenytoin metformin phenobarbital dihydrofolate reductase inhibitors (trimethoprim, pyrimethamine) methotrexate sulfonamides valproic acid.

History findings to help identify folate deficiency are as follows Poor nutrition, alternative diets, and excessive heating and dilution of foods Chronic alcoholism Conditions that interfere with folate absorption, including inflammatory bowel disease, sprue or gluten sensitivity, and amyloidosis Conditions that increase folate consumption, such as pregnancy, lactation, hemolytic anemia, hyperthyroidism, and exfoliative dermatitis Hyperalimentation and hemodialysis Medications that affect folate (see the list in Etiology) Hereditary disorder: A lifelong history of megaloblastosis or folate deficiency would suggest a hereditary disorder as the cause.

25 MEGALOBLASTIC ANEMIAS clinical features 1- Asymptomatic for years 2-Symptoms of anemia(weakness and cardiopulmonary impairement) 3- Symptoms associated with vit. B 12 or Folic acid deficiency neurologic manifestations (exclusivly in wit. B 12 deficiency) - megaloblastic madness or psychosis, - subacute, combined degeneration of the spinal cord ( proprioceptive and vibratory sensation), spinal ataxia with unsteady gait and abnormal balance. -Peripheral neuropathy (numbness, pain, tingling, and burning in a patient’s hands and feet in glove and stocking distribution). gastrointestinal compraints (vit.B 12 and folic acid deficiency) - loss of appetite - glossitis (red, sore, smooth tongue) - diarrhea or constipation - weight loss

c/p: signs: Patients may have a lemon-yellow complexion (combined anemia and increased indirect bilirubin from intramedullary hemolysis) Anemia signs(tachycardia, dyspnea) Glossitis ( with loss of papilla) Dermatologic signs include hyperpigmentation of the skin and abnormal pigmentation of hair due to increased melanin synthesis Mental changes of psychosis Peripheral neuropathy SCD of cord and abnormal gait. Blindness due to optic atrophy may occur. signs of the cause.

Signs suggestive of the cause: Abdominal scars may suggest a blind loop syndrome due to gastric surgery or a lack of ileal absorption of cobalamin in a patient who had an ileal resection. Patients with nontropical and tropical sprue may have signs of malabsorption, such as weight loss, abdominal distention, diarrhea, and steatorrhea. These patients often have metabolic bone disease or bleeding resulting from to deficiencies in vitamin K–dependent factors. Patients who have megaloblastosis as a result of HIV infection or myelodysplastic syndromes usually have signs of these disorders. Children with inborn errors associated with folate and cobalamin deficiencies may have signs of these hereditary disorders.

Subacute combined degeneration of the cord Degeneration and demyelination of the dorsal (posterior) and lateral spinal columns.

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

Lab work out: Reticulocyte counts are inappropriately low, representing lack of production of RBCs due to massive intramedullary hemolysis LDH is usually markedly increased Peripheral smear morphology: Macroovalocytes Single and multiple Howell-Jolly bodies, nuclear fragment, may be seen in RBCs. Cabot rings, remnants of mitotic spindles, may also be present in RBCs. Nucleated RBCs and megaloblasts hypersegmented neutrophils pancytopenia

Cabot rings in RBCs

Megaloblastic anemia Megaloblastic BM Hypersegmented PMN

Bone marrow aspiration Bone marrow aspiration is usually not needed to make the diagnosis of vitamin B-12 deficiency. However, it can help rule out myelodysplasia and assess iron stores. The bone marrow is hypercellular with erythroid hyperplasia Giant bands, neutrophil precursers, can be present. Megakaryocytes may be large and hyperlobulated.

Primary Tests for B-12 and Folate Deficiencies Serum B-12 (cobalamin) Reference range: pg/mL Borderline: pg/mL Associated with anemia and neuropathy: < 180 mg/L Diagnostic of B-12 deficiency: < 150 mg/L Serum folate Reference range: ng/mL 5 ng/mL Folate deficiency likely (overlap with normal): < 2.5 ng/mL RBC folate:

Lab tests to confirm and distinguish B-12 and folate deficiencies Folate deficiencyB12 deficiency ↑↑ homocysteine ↔↑ MMA Intrinsic factor (IF) blocking and parietal cell and antibodies IF antibodies, type 1 and type 2, occur in 50% of patients with pernicious anemia Parietal cell antibody occurs in 90% of patients. with pernicious anemia. Both tests are non Specific. (Schilling test) not done now.

Other needed tests: Baseline iron studies and serum ferritin should be obtained since they may predict the need for iron therapy since iron stores can be consumed during cobalamin or folate therapy. Radiographic imaging of the upper and lower GIT may be useful for detecting abnormalities that could cause a blind loop syndrome Other tests that may be considered include : With cobalamin deficiency, evaluate and rule out autoimmune disorders, Zollinger-Ellison syndrome, pancreatic insufficiency, fish tapeworm infestation, Crohn disease, or ileal scarring. With folate deficiency, evaluate evidence for malnutrition and alcoholism, sprue, chronic hemolysis, and exfoliative dermatitis. Megaloblastic anemia

THERAPY: Transfusion therapy should be restricted to patients with severe, uncompensated, and life-threatening anemia. Cobalamin Therapy Cobalamin (1000 µg) should be given intramuscularly daily for 2 weeks, then weekly until the hematocrit value is normal, and then monthly for life. Oral cobalamin ( µg) also can be administered.

Note the following: Oral cobalamin is indicated in patients with hemophilia to avoid intramuscular injections and bleeding. Intramuscular cobalamin and not oral cobalamin should be used to treat patients with cobalamin-related neurological disorders. One advantage of parenteral over oral cobalamin is that all abnormalities in cobalamin absorption are bypassed. It may be practical to initially administer parenteral cobalamin and then to continue treatment with oral cobalamin. Oral cobalamin is less expensive and is better tolerated by patients. Patients who have undergone either a total or partial gastrectomy should be started on replacement therapy after the surgery to prevent the development of megaloblastosis

Folate Therapy Folate (3-5 mg) should be administered orally. Folate should be administered prophylactically during pregnancy, lactation, and the perinatal period. Folate is also indicated in patients with chronic hemolytic anemias, psoriasis and exfoliative dermatitis, and during extensive renal dialysis. Folate therapy has been recommended in patients with hyperhomocysteinemia who are at risk for thromboembolic complication Fortification of foods and folic acid supplements have been recommended to reduce the risk of pancreatic, cervical, and colon cancers. Folic acid supplements are indicated in end-stage renal disease. Folate supplementation is indicated in elderly persons

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

Warning Folate therapy should not be instituted in a patient with megaloblastic anemia if cobalamin deficiency has not been definitively ruled out. The danger is that folic acid will improve the anemia but not the neurological complications of cobalamin deficiency, and the neurological disorder will worsen. Both cobalamin and folate should be initiated if cobalamin deficiency has not been ruled out

Treatment of Other Related Conditions Blind loop syndrome should be treated with antibiotics. Patients with transcobalamin II (TCII) deficiency may require higher doses of cobalamin. Tropical sprue should be treated with both cobalamin and folate. Acute megaloblastic anemias due to nitrous oxide exposure can be treated with folate and cobalamin. Fish tapeworm infection, pancreatitis, Zollinger-Ellison syndrome, and inborn errors should be treated with appropriate measures.

diet Patients should have diets rich with folic acid. Examples of such foods include asparagus, broccoli, spinach, lettuce, lemons, bananas, melons, liver, and mushrooms. To prevent loss of folate, foods should not be cooked excessively and should not be diluted in large amounts of water. To prevent cobalamin deficiency, vegetarians should include dairy products and eggs in their meals

Prognosis The prognosis is favorable if the etiology of megaloblastosis has been identified and appropriate treatment has been instituted. However, patients are at risk for hypokalemia and anemia-related cardiac complications during therapy for cobalamin deficiency. Folate deficiency during pregnancy can lead to neural tube defects and other developmental disorders in the fetus. However, folate in prenatal vitamins given during pregnancy has reduced these morbidities