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↓ in RBC mass: Hct <41% or Hb <13.5 g/dL (men); Hct <36% or Hb <12 g/dL (women)

Clinical manifestations

•  Symptoms: ↓ O2 delivery → fatigue, exertional dyspnea, angina (if CAD)

•  Signs: pallor (mucous membranes, palmar creases), tachycardia, orthostatic hypotension

•  Other findings: jaundice (hemolysis), splenomegaly (thalassemia, neoplasm, chronic hemolysis), petechiae/purpura (bleeding disorder), glossitis (iron, folate, vitamin B12 defic.), koilonychia (iron defic.), neurologic abnormalities (B12 defic.)

Diagnostic evaluation

•  History: bleeding, systemic illness, drugs, exposures, alcohol, diet (including pica), FHx

•  CBC w/ diff.; RBC params incl. retics, MCV (nb, mixed disorder can → nl MCV), RDW

•  Reticulocyte index (RI) = [reticulocyte count × (Pt’s Hct/nl Hct)]/maturation factor maturation factors for a given Hct: 45% = 1, 35% = 1.5, 25% = 2, 20% = 2.5
RI >2% → adequate marrow response; RI <2% → hypoproliferation

•  Peripheral smear: select area where RBCs evenly spaced and very few touch each other; ✓ RBC size, shape, inclusions (see Appendix & Peripheral Smear inserts), WBC morphology, plt count

•  Additional labs as indicated: hemolysis labs (if RI >2%), iron/TIBC, ferritin, folate, B12, LFTs, BUN and Cr, TFTs, Hb electrophoresis, enzyme analyses, gene mutation screens

•  Bone marrow (BM) aspirate and biopsy (bx) with cytogenetics as indicated

Figure 5-1 Approach to anemia


Figure 5-2 Approach to microcytic anemias

Iron deficiency (NEJM 1999;341:1986; Gut 2011;60:1309)

•  ↓ marrow iron & depleted body iron stores → ↓ heme synthesis → microcytosis → anemia

•  Special clinical manifestations: angular cheilosis, atrophic glossitis, pica (consumption of nonnutritive substances such as ice, clay), koilonychia (nail spooning) Plummer-Vinson syndrome (iron deficiency anemia, esophageal web & atrophic glossitis)

•  Etiologies: chronic bleeding (GI—incl. cancer, menstrual, parasites, etc.), ↓ supply (malnutrition; ↓ absorp. due to celiac sprue, Crohn’s, ↑ gastric pH, subtotal gastrectomy), ↑ demand (preg., Epo). Rare Fe refractory genetic disorder due to hepcidin dysregulation (Nat Genet 2008;40:569).

•  Diagnosis: ↓ Fe, ↑ TIBC, ↓ ferritin (esp. <15), ↓ transferrin sat (Fe/TIBC; esp. <15%), ↑ soluble transferrin receptor; ↑ plt; unless hx c/w other etiology, initiate workup for GIB; incl. H. pylori serology, ? celiac sprue labs (anti-TTG, antigliadin, antiendomysial Ab)

•  Treatment (Fe supplementation): oral Fe tid (~6 wk to correct anemia; ~6 mo to replete Fe stores); in cases of excessive/persistent GI losses or for dialysis or cancer Pts prior to Epo Rx, IV iron (Fe-sucrose, -gluconate, -dextran) should be considered

Thalassemias (Lancet 2013;379:373)

•  ↓ synthesis of ɑ- or β-globin chains of Hb → ≠ subunits → destruction of RBCs and erythroid precursors; ∴ anemia from hemolysis and ineffective erythropoiesis

•  ɑ-thalassemia: deletions in ɑ-globin gene complex on chr. 16 (nl 4 ɑ genes)
3 ɑ → ɑ-thal-2 trait = silent carrier; 2 ɑ → ɑ-thal-1 trait or ɑ-thal minor = mild anemia
1 ɑ → HbH (β4) disease = severe anemia, hemolysis and splenomegaly
0 ɑ genes → Hb Barts (γ4) = intrauterine hypoxia and hydrops fetalis

•  β-thalassemia: mutations in β-globin gene on chr. 11 → absent or ↓ gene product
1 mutated β gene → thal minor (or trait) = mild anemia (no transfusions)
2 mutated β genes → thal intermedia (occasional transfusions) or thal major ( = Cooley’s anemia; transfusion dependent) depending on severity of mutations

•  Special clinical manifestations (in severe cases): chipmunk facies, pathologic fractures, hepatosplenomegaly (due to extramedullary hematopoiesis), high-output CHF, bilirubin gallstones, iron overload syndromes (from chronic transfusions)

•  Diagnosis: MCV <70, normal FeMCV/RBC count<13 [Mentzer Index, 60% Se, 98% Sp; (Ann Hem 2007;86:486)], ± ↑ retics, basophilic stippling; Hb electrophoresis: ↑ HbA2 (ɑ2δ2) in β-thal;normal pattern in ɑ-thal trait

•  Treatment: folate; transfusions + deferoxamine, deferasirox (oral iron chelator); splen-ectomy if ≥50% ↑ transfusions; consider allo-HSCT in children w/ severe β-thal major

Anemia of chronic inflammation (see below)

Sideroblastic anemia

•  Defective heme biosynthesis within RBC precursors

•  Etiologies: hereditary/X-linked (ALAS2 mutations), idiopathicMDS-RARSreversible (alcohol, lead, isoniazid, chloramphenicol, copper deficiency, hypothermia)

•  Special clinical manifestations: hepatosplenomegaly, iron overload syndromes

•  Dx: review social, work & TB hx; can be microcytic, normocytic or macrocytic; variable pop of hypochromic RBCs; ↑ Fe, nl TIBC, ↑ ferritin, basophilic stippling, RBC Pappenheimer bodies (Fe-containing inclusions), ring sideroblasts (w/ iron-laden mitochondria) in BM

•  Treatment: treat reversible causes; trial of pyridoxine, supportive transfusions for severe anemia; high-dose pyridoxine for some hereditary cases


Pancytopenia (see below)
Anemia of chronic inflammation (ACI; NEJM 2005;352:1011; 2009;361:1904)

•  ↓ RBC production due to impaired iron utilization and functional iron deficiency from ↑ hepcidin; cytokines (IL-6, TNF-a) cause ↓ Epo responsiveness/production

•  Etiologies: autoimmune disorders, chronic infection, inflammation, HIV, malignancy

•  Dx: ↓ Fe, ↓ TIBC (usually normal or low transferrin sat), ± ↑ ferritin; usually normochromic, normocytic (~70% of cases) but can be microcytic if prolonged

•  Coexisting iron deficiency common. Dx clues include ↓ serum ferritin levels, absence of iron staining on BM bx,  response to a trial of oral iron and/or ↑ soluble transferrin receptor/ferritin index (Blood1997;89:1052).

•  Treatment: treat underlying disease ± iron and/or erythropoiesis-stimulating agent (ESA, eg, Epo). Iron if ferritin <100 or Fe/TIBC <20%. Consider ESA if Epo <500. Avoid ESA in cancer if treatment goal is cure (Leuk Res 2012;36:939). Unclear if one should treat highly sx Pts w/ goal Hb 10–12 g/dL; weigh risk of thrombosis.

Anemias of chronic disorders

•  Anemia of chronic inflammation (see above)

•  Anemia of chronic kidney disease: ↓ Epo; treat w/ Epo (see “Chronic Kidney Disease”)

•  Endocrine deficiencies: hypometabolism and ↓ O2 demand with thyroid, pituitary, adrenal, or parathyroid disease → ↓ Epo; can be normocytic or macrocytic

Sideroblastic anemia (see above)
Pure red cell aplasia

•  Destructive antibodies or lymphocytes → ineffective erythropoiesis

•  Associated with thymoma, CLL and parvovirus infection

•  Diagnostic studies: lack of erythroid precursors on BM bx, other lines normal

•  Treatment: thymectomy if thymus enlarged; IVIg if parvovirus infection; immunosuppression if CLL or idiopathic; supportive care with PRBC transfusions; ? erythropoietin receptor agonist if due to antierythropoietin Ab (NEJM 2009;361:1848)


includes megaloblastic and nonmegaloblastic causes

Megaloblastic anemia

•  Impaired DNA synthesis → cytoplasm matures faster than nucleus → ineffective erythropoiesis and macrocytosis; due to folate or B12 deficiencyMDS

•  ✓folate and vitamin B12; ↑ LDH & indirect bilirubin (due to ineffective erythropoiesis)

•  Smear: neutrophil hypersegmentationmacro-ovalocytes, anisocytosis, poikilocytosis

Folate deficiency

•  Folate present in leafy green vegetables and fruit; total body stores sufficient for 2–3 mo

•  Etiologies: malnutrition (alcoholics, anorectics, elderly), ↓ absorption (sprue), impaired metabolism (methotrexate, pyrimethamine, trimethoprim), ↑ requirement (chronic hemolytic anemia, pregnancy, malignancy, dialysis)

•  Diagnosis: ↓ folate; ↓ RBC folate, ↑ homocyst. but nl methylmalonic acid (unlike B12 defic.)

•  Treatment: folate 1–5 mg PO qd for 1–4 mo or until complete hematologic recovery; critical to r/o B12 deficiency first (see below)

Vitamin B12 deficiency (NEJM 2013;368:149)

•  B12 present only in foods of animal origin; total body stores sufficient for 2–3 y

•  Binds to intrinsic factor (IF) secreted by gastric parietal cells; absorbed in terminal ileum

•  Etiologies: malnutrition (alcoholics, vegans), pernicious anemia (PA, autoimmune dis- ease against gastric parietal cells, a/w polyglandular endocrine insufficiency and ↑ risk of gastric carcinoma), other causes of ↓ absorption (gastrectomy, sprue, Crohn’s disease), ↑ competition (intestinal bacterial overgrowth, fish tapeworm)

•  Clinical manifestations: neurologic changes (subacute combined degeneration) affecting peripheral nerves, posterior and lateral columns of the spinal cord and cortex → numbness, paresthesias, ↓ vibratory and positional sense, ataxia, dementia

•  Dx: ↓ B12; ↑ homocysteine and methylmalonic acid; anti-IF Ab; Schilling test; ↑ gastrin in PA

•  Treatment: 1 mg B12 IM qd × 7 d → q wk × 4–8 wk → q month for life neurologic abnormalities are reversible if treated w/in 6 mo folate can reverse hematologic abnormalities of B12 deficiency but notneurologic changes (and can lead to “steal” of B12 stores → worsening of neuro complications) oral supplementation (2 mg qd) appears feasible as well (Blood 1998;92:1191) even w/o IF

Nonmegaloblastic macrocytic anemias

•  Liver disease: often macrocytic, may see target cells

•  Alcoholism: BM suppression & macrocytosis independent of folate/B12 defic. or cirrhosis

•  Reticulocytosis

•  Other causes: hypothyroidism; MDS; meds that impair DNA synthesis (zidovudine, 5-FU, hydroxyurea, Ara-C); hereditary orotic aciduria; Lesch-Nyhan syndrome.



•  Hypocellular bone marrow (nl cellularity ~100 – age): aplastic anemia, hypoplastic MDS

•  Cellular bone marrow: MDS, aleukemic leukemia, PNH, severe megaloblastic anemia

•  Marrow replacement (myelophthisis): myelofibrosis, metastatic solid tumors, granulomas

•  Systemic diseases: hypersplenism, sepsis, alcohol, toxins

Clinical manifestations

•  Anemia → fatigue

•  Neutropenia → recurrent infections

•  Thrombocytopenia → mucosal bleeding & easy bruisability

Aplastic anemia = stem cell failure (Lancet 2005;365:1647; Blood 2012;120:1185)

•  Epidemiology: 2–5 cases/106/y; biphasic (major peak in adolescents, 2nd peak in elderly)

•  Diagnosis: pancytopenia w/ ↓ retics, BM bx w/ cytogenetics showing hypocellularity

•  Etiologies: idiopathic (1/2 –1/3 of cases)

stem cell destructionradiationchemotherapychemicals (eg, benzene) idiosyncratic med rxn (eg, chloramphenicol, NSAIDs, sulfa drugs, gold, carbamazepine, antithyroid)

viruses (HHV-6, HIV, EBV, parvovirus B19); also post-hepatitis (non A, B or C)

immune disorders (SLE, GVHD post-HSCT, thymoma)

PNH (see below); Fanconi’s anemia (congenital disorder w/ pancytopenia, macrocytic anemia, ↑ risk of MDS, AML, & SCC of head & neck, and multiple physical anomalies);

shortened telomeres: seen w/ telomerase (TERT, TERC) mut (10% of aplastic anemia), dyskeratosis congenita/DKC1 mut; a/w IPF, cirrhosis (NEJM 2009;361:2353)

•  Treatment and prognosis

allogeneic HSCT: for young Pts → ~80% long-term survival and significantly ↓ risk of malignant evolution, but has risk of transplant-related morbidity & mortality; if possible avoid transfusions (and alloimmunization) pretransplant

immunosuppression (CsA/tacrolimus,  ATG): 70–80% respond, with 80–90% 5-y survival in responders (96% vs. 76% w/ horse vs. rabbit ATG; NEJM 2011;365:430); 15–20% 10-y incidence of clonal disorders (mostly MDS,  AML, PNH)

TPO mimetics (eg, eltrombopag) may be option in refractory disease (NEJM 2012;367:11)

supportive care: transfusions, antibiotics, possible utility of G-CSF and Epo

Myelodysplastic syndromes (MDS) (qv)

Paroxysmal nocturnal hemoglobinuria (PNH) (Blood 2009;113:6522)

•  Acquired clonal stem cell disorder = inactivating somatic mutation of PIG-A gene → deficiency of GPI-anchor for CD55 & CD59 (inhib of complement) → complement-mediated RBC lysis, plt aggreg., & hypercoagulability

•  Clinical: intravascular hemolytic anemiahypercoagulability (venous > arterial; esp. intraabdominal, cerebral), smooth muscle dystonias, deficient hematopoiesis (cytopenias); a/w aplastic anemia, MDS and evolution to AML

•  Dx: flow cytometry (↓ CD55 & CD59) on RBCs and granulocytes; urine hemosiderosis

•  Treatment: supportive care (iron, folate, transfusions); consider anti-coagulation allogeneic HSCT for hypoplasia or severe thrombosis eculizumab (Ab inactivates terminal complement C5s): ↓ hemolysis, improves QoL & stabilizes Hb levels (NEJM 2004;350:552 & 2006;355:1233; Lancet 2009;373:759); must have meningococcal vaccination

Myelophthisic anemia (see also “Primary Myelofibrosis”)

•  Infiltration of bone marrow by cancer, leukemia, infection, fibrosis (primary myelofi- brosis), granulomas, lysosomal storage disorders


Diagnostic evaluation

•  ↑ reticulocyte count (RI >2%), ↑ LDH, ↓ haptoglobin (83% Se, 96% Sp), ↑ indirect bili

•  Autoimmune hemolysis: Coombs’ test = direct antiglobulin test (DAT) →  if agglutination occurs when antisera against Ig or C3 are applied to patient RBCs

•  Intravascular: ↑↑ LDH, ↓↓ haptoglobin; hemoglobinemia, hemoglobinuria, hemosiderinuria

•  Extravascular: splenomegaly

•  Family h/o anemia; personal or family h/o cholelithiasis

Glucose-6-phosphate dehydrogenase (G6PD) deficiency (Lancet 2008;371:64)

•  X-linked defect of metabolism (G6PD mutations) w/ ↑ susceptibility to oxidative damage

•  Most common in  of African or Mediterranean descent (malaria-endemic areas)

•  Hemolysis precipitated by drugs (sulfonamides, dapsone, primaquine, doxorubicin, methylene blue), infectionDKA or foods (fava beans in children)

•  Diagnosis: smear may show RBC Heinz bodies (oxidized Hb) that result in bite cells once removed by spleen; ↓ G6PD levels (may be normal after acute hemolysis as older RBCs have already lysed and young RBCs may still have near normal levels)

Sickle cell anemia (Lancet 2010;376:2018)

•   Recessive β-globin mutation → structurally abnl hemoglobin (HbS). ~8% African Americans heterozygotes (“sickle trait”; usually w/o sx); ~1/400 homozygotes (sickle cell disease).

•  ↓ O2 → HbS polymerizes → RBC sickles, ↓ RBC deformability → hemolysis & microvascular occlusion

•  Anemia: chronic hemolysis ± acute aplastic (parvo. B19) or splenic sequestration crises

•  Vaso-occlusion and infarction: painful crises, acute chest syndrome, CVA, splenic sequestration, hand-foot syndrome, renal papillary necrosis, aseptic necrosis, priapism

•  Infection: splenic infarction → overwhelming infection by encapsulated organisms; infarcted bone → osteomyelitis (SalmonellaStaph. aureus)

•  Diagnosis: sickle-shaped RBCs and Howell-Jolly bodies on smear; Hb electrophoresis

•  Treatment: hydroxyurea causes ↑ HbF → ↓ painful crises, acute chest episodes and may ↓ mortality (NEJM 2008;358:1362); allogeneic HSCT may have a role in young Pts w/ severe disease (Blood2000;95:1918) and adults (NEJM 2009;361:2309)

•  Supportive care: folic acid qd; pneumococcal, meningococcal, H. flu & HBV vaccination; pain crises treated with hydrationoxygen and analgesia; simple or exchange transfusion for TIA or stroke, severe acute chest syndrome, or preop (goal Hb 10 g/dL)

Hereditary spherocytosis (HS) (Br J Hematol 2004;126:455)

•  Defect in a cytoskeletal protein of RBC membrane → membrane loss mutations in ankyrin, a- and β-spectrin, band 3 and pallidin have been identified

•  Most common in N. European populations (1/5000 births);  FHx (75% of Pts)

•  Anemia, jaundice (mostly neonates), splenomegaly, pigmented gallstones

•  Diagnosis: spherocytes on smear,  osmotic fragility test (~80% Se), ↓ eosin-5-maleimide (EMA) binding (92% Se; 99% Sp)

•  Treatment: folate, transfusions, splenectomy for moderate and severe HS (balance w/ ↑ risk of future thrombosis and infection (J Thromb Haemost 2008;6:1289)

Paroxysmal nocturnal hemoglobinuria (see above)

Autoimmune hemolytic anemia (AIHA)

•  Acquired, antibody-mediated RBC destruction

•  Warm AIHAIgG Abs opsonize RBCs at body temp → removal by spleen Etiologies: idiopathic, lymphoproliferative (CLL, NHL), autoimmune (SLE), drugs

•  Cold AIHAIgM Ab binds to RBCs at temp <37°C → complement fixation → intravascular hemolysis and acrocyanosis on exposure to cold

Etiologies: idiopathic, lymphoprolif. disorders (eg, Waldenström’s; monoclonal), Mycoplasma pneumoniae infxn and infectious mononucleosis (polyclonal)

•  Diagnosis: spherocytes on smear,  Coombs’; ✓ cold agglutinin titer, splenomegaly

•  Treatment: treat underlying disease

warm AIHA: corticosteroids ± splenectomy, IVIg, cytotoxic agents, rituximab

cold AIHA: avoid cold; steroids ineffective; rituximab (Blood 2004;103:2925)

Drug-induced hemolytic anemia

•  Acquired, antibody-mediated, RBC destruction precipitated by a medication:

abx: cephalosporins, sulfa drugs, rifampin, ribavirin

CV: methyldopa, procainamide, quinidine, thiazides

TCAs, phenothiazines, NSAIDs, sulfonylureas, MTX, 5-FU, rasburicase (G6PD defic.)

•  Diagnosis: Coombs’ usually negative, ↑ LDH

• Treatment: discontinue offending agent

Microangiopathic hemolytic anemia (MAHA)

•  Intra-arteriolar fibrin damages RBCs → acquired intravascular hemolysis

•  Etiologies: hemolytic-uremic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP), disseminated intravascular coagulation (DIC), malignancy, malignant HTN, eclampsia/HELLP, mech. cardiac valves, infected vascular prostheses

•  Diagnosis: schistocytes ± thrombocytopenia ± abnormalities a/w specific disorders (eg, ↑ PT in DIC, ↑ Cr in HUS, ↑ LFTs in HELLP)

•  Treatment: treat underlying abnormality; urgent plasma exchange for TTP


• Stasis/trapping in spleen → mf attack & remodeling of RBC → spherocytosis → hemolysis