Anemia

Resident Survival Guide

Anemia main page
Overview
Classification
Differential Diagnosis
Medical Therapy

For patient information click here

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Shyam Patel [2] Associate Editor(s)-in-Chief: Sargun Singh Walia M.B.B.S.[3], Vamsikrishna Gunnam M.B.B.S [4], Mehrian Jafarizade, M.D [5]

Synonyms and keywords: Anaemia; low hemoglobin; low hemoglobin levels (peripheral blood)

Overview

Anemia is the most common disorder of the blood. Anemia, from the Greek (Ἀναιμία) (an-haîma) meaning "without blood", is a deficiency of red blood cells (RBCs) and/or hemoglobin. This results in a reduced ability of blood to transfer oxygen to the tissues, causing tissue hypoxia. Since all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences. Hemoglobin (the oxygen-carrying protein in the red blood cells) must be present to ensure adequate oxygenation of all tissues and organs.

The three main classes of anemia include excessive blood loss (acutely such as a hemorrhage or chronically through low-volume loss), excessive blood cell destruction (hemolysis), or deficient red blood cell production (ineffective hematopoiesis). There are multiple subtypes of anemia within those major categories. Anemia is defined as a hemoglobin concentration (Hb) of less than 12 g/dL in women and less than 13 g/dL in men, or alternatively, hematocrit of less than 36% in women and less than 40% in men.

Classification

Here is a simplified schematic of this approach:

Anemia

Reticulocyte production index shows inadequate production response to anemia.

Reticulocyte production index shows appropriate response to anemia = ongoing hemolysis or blood loss without RBC production problem.

No clinical findings consistent with hemolysis or blood loss: pure disorder of production.

Clinical findings and abnormal MCV: hemolysis or loss and chronic disorder of production*.

Clinical findings and normal MCV= acute hemolysis or loss without adequate time for bone marrow production to compensate**.

Macrocytic anemia (MCV>100)

Normocytic anemia (80<MCV<100)

Microcytic anemia (MCV<80)

* For instance, sickle cell anemia with superimposed iron deficiency; chronic gastric bleeding with B12 and folate deficiency; and other instances of anemia with more than one cause. ** Confirm by repeating reticulocyte count: ongoing combination of low reticulocyte production index, normal MCV and hemolysis or loss may be seen in bone marrow failure or anemia of chronic disease, with superimposed or related hemolysis or blood loss.

Classification Based on Red blood Cell Size

Here is a schematic representation of how to consider anemia with MCV as the starting point:

Anemia

Macrocytic anemia (MCV>100)

Normocytic anemia (80<MCV<100)

Microcytic anemia (MCV<80)

High reticulocyte count

Low reticulocyte count

Other characteristics visible on the peripheral smear may provide valuable clues about a more specific diagnosis; for example, abnormal white blood cells may point to a cause in the bone marrow.

Microcytic Anemia

Microcytic anemia is primarily a result of hemoglobin synthesis failure/insufficiency, which could be caused by several etiologies:

• Heme synthesis defect
  • Iron deficiency
  • Anemia of Chronic Disorders (more commonly presenting as normocytic anemia)
• Globin synthesis defect
  • Alpha- and beta-thalassemia
  • HbE syndrome
  • HbC syndrome
  • Various other unstable hemoglobin diseases
• Sideroblastic defect
  • Hereditary sideroblastic anemia
  • Acquired sideroblastic anemia including lead toxicity
  • Reversible sideroblastic anemia

• Iron deficiency anemia is the most common type of anemia overall and it has many causes. RBCs often appear hypochromic (paler than usual) and microcytic (smaller than usual) when viewed with a microscope.
• Hemoglobinopathies are much rarer (apart from communities where these conditions are prevalent) such as Southeast Asia.

Normocytic Anemia

Normocytic anaemia occurs when the overall Hb levels are decreased, but the red blood cell size (MCV) remains normal. Causes include:

• Acute blood loss
• Anemia of chronic disease
• Aplastic anemia (bone marrow failure)
• Hemolytic anemia
• Erythropoietin deficiency
• Renal failure
• Early phase of acute blood loss

Macrocytic Anemia

• Megaloblastic anemia is the most common cause of macrocytic anemia.
• Megaloblastic anemia is due to a deficiency of either vitamin B12, folic acid (or both), or to autoimmune processes that cause deficiency in either, such as pernicious anemia. Liver disease and hypothyroidism can also contribute to megaloblastic anemia. Deficiency in folate and/or Vitamin B12 can be due either to inadequate intake or insufficient absorption. Folate deficiency normally does not produce neurological symptoms, while B12 deficiency does.
• Alcoholism causes a macrocytosis, although not specifically anemia.
• Methotrexate, zidovudine, and other drugs that inhibit DNA replication. This is the most common etiology in nonalcoholic patients.

Specific Anemias

• Anemia of prematurity occurs in premature infants at 2 to 6 weeks of age and results from diminished erythropoietin response to declining hematocrit levels.
• Fanconi anemia is an hereditary disorder or defect featuring aplastic anemia and various other abnormalities.
• Hemolytic anemia causes a separate constellation of symptoms (also featuring jaundice and elevated LDH levels) with numerous potential causes. It can be autoimmune, immune, hereditary or mechanical (e.g. heart surgery). It can result (because of cell fragmentation) in a microcytic anemia, a normochromic anemia, or (because of premature release of immature red blood cells from the bone marrow), a macrocytic anemia.
• Hereditary spherocytosis is a hereditary defect that results in defects in the RBC cell membrane, causing the erythrocytes to be sequestered and destroyed by the spleen. This leads to a decrease in the number of circulating RBCs and, hence, anemia.
• Sickle-cell anemia, a hereditary disorder, is due to homozygous hemoglobin S genes.
• Warm autoimmune hemolytic anemia is an anemia caused by autoimmune attack against red blood cells, primarily by IgG. This is responsive to corticosteroid therapy.
• Cold agglutinin hemolytic anemia is primarily mediated by IgM. This is not responsive to corticosteroid therapy but is responsive to rituximab.
• Pernicious anemia is a form of megaloblastic anaemia due to vitamin B12 deficiency dependent on impaired absorption of vitamin B12. It is due to loss of intrinsic factor in the gastrointestinal tract.
• Myelophthisic anemia or Myelophthisis is a severe type of anemia resulting from the replacement of bone marrow by other materials, such as malignant tumors or granulomas.

Differentiating Anemia from Other Diseases

Anemia must be differentiated based on different laboratory findings including mean cell volume (MCV), reticulocytosis, and hemolysis.

To review the differential diagnosis of anemia, see below table.

To review the differential diagnosis of microcytic anemia, click here.

To review the differential diagnosis of normocytic anemia, click here.

To review the differential diagnosis of macrocytic anemia, click here.

To review the differential diagnosis of hypochromic anemia, click here.

To review the differential diagnosis of normochromic anemia, click here.

To review the differential diagnosis of anisochromic anemia, click here.

To review the differential diagnosis of hemolytic anemia, click here.

To review the differential diagnosis of anemia with intrinsic hemolysis, click here.

To review the differential diagnosis of anemia with extrinsic hemolysis, click here.

To review the differential diagnosis of anemia with low reticulocytosis, click here.

To review the differential diagnosis of anemia with normal reticulocytosis, click here.

To review the differential diagnosis of anemia with high reticulocytosis, click here.

Disease	Genetics	Clinical manifestation					Lab findings
		History	Symptoms	Signs	Hemolysis	Intrinsic/ Extrinsic	Hb concentration	MCV	RDW	Reticulocytosis	Haptoglobin levels	Hepcidin	Iron studies					Specific finding on blood smear
													Serum iron	Serum Tfr level	Transferrin or TIBC	Ferritin	Transferrin saturation
Iron deficiency anemia	−	Menorrhagia GI loss GI surgery Pregnancy	Koilonychia Pica	Glossitis Cheilosis Dysphagia	−	−	Hypochromic	Microcytic	↑	Nl or ↓	Nl	Nl	↓	↑	↑	↓	↓↓↓	Central pallor
Iron deficiency anemia (early phase)	−	Pica Glossitis Cheilosis	Fatigue Headache	Koilonychia Conjunctival pallor Dry skin	−	−	Normochromic	Normocytic	↑	↓	Nl	Nl	↓	↑	↑	↓	↓	Pencil cells Elliptocytosis Hypochromasia
Lead poisoning	−	House painted with chipped paint	Burtonian lines Basophilic stippling Wrist drop Foot drop	Wrist drop Foot drop Burtonian lines	−	−	Hypochromic	Microcytic	Nl	Nl or ↓	Nl	Nl	Nl to ↓	Nl	Nl	Nl to ↓	−	RBCs retain aggregates of rRNA Basophilic stippling
Sideroblastic anemia	Defect in ALA synthase gene Autosomal dominant Autosomal recessive X-linked	Alcohol abuse Isoniazid use Chloramphenicol use Lead poisoning Idiopathic	Seborrheic dermatitis Glossy Tongue Tingling	Patient present with symptoms of Vitamin B6, copper deficiency symptoms	−	−	Hypochromic	Microcytic	Nl	Nl or ↓	Nl	Nl	↑	Nl	Nl to ↓	↑	−	Ringed sideroblasts
Disease	Genetics	History	Symptoms	Signs	Hemolysis	Intrinsic/ Extrinsic	Hb concentration	MCV	RDW	Reticulocytosis	Haptoglobin levels	Hepcidin	Serum iron	Serum Tfr level	IBC	Ferritin	Transferrin saturation	Specific finding on blood smear
Anemia of chronic disease	−	Rheumatoid arthritis SLE Neoplasm Chronic kidney disease	Headache Shortness of breath	−	−	−	Hypochromic	Microcytic	Nl	Nl or ↓	Nl	↑	↓	Nl	↓	↑	−	NA
Thalassemia	α-thalassemia α- globin gene deletions Cis deletions Trans deletions β-thalassemia Point mutation in splice sites and promoter sequences	Associated with parvovirus B19	α-thalassemia Hydrops fetalis β-thalassemia Skeletal deformities Chipmunk facies	Hepatomegaly Splenomegaly	−	−	Hypochromic	Microcytic	Nl	Thalassemia trait: Nl or ↓ Thalassemia Syndromes: ↑	Nl	Nl	Nl to ↑	Nl	Nl	↑	Nl to ↑	Target cells Anisopoikilocytosis
G6PD deficiency	Defect in G6PD enzyme X-Linked recessive	History of using Sulfa drugs Antimalarials Fava Beans Infections	Back pain Hemoglobinuria	Back pain	+	Intrinsic	Normochromic	Normocytic	↑	↑ but usually causes resolution within 4-7 days	↓	↓	Nl to ↑	Nl	↑	↑	↑	RBC with Heinz bodies Bite cells Blister cells
Pyruvate kinase deficiency	Mutation in the PKLR and PKM gene Autosomal recessive	Gallstones	Hydrops fetalis Neonatal hyperbilirubinemia Iron overload Perinatal complications	Skin ulcers Splenomegaly	+	Intrinsic	Normochromic	Normocytic	↑	↑	↓	Nl	↑	Nl	Nl	↑	−	Prickle cells Polychromatophilic erythrocytes
Disease	Genetics	History	Symptoms	Signs	Hemolysis	Intrinsic/ Extrinsic	Hb concentration	MCV	RDW	Reticulocytosis	Haptoglobin levels	Hepcidin	Serum iron	Serum Tfr level	IBC	Ferritin	Transferrin saturation	Specific finding on blood smear
Sickle cell anemia	Hbs point mutation causes a single amino acid replacement in β chain	High altitude Low Oxygen Acidosis African-American race Parvovirus B19 infection	Painful crisis Dactylitis Priapism Acute chest syndrome Avascular Necrosis Stroke Autosplenectomy Salmonella osteomyelitis	Dactylitis Priapism	+	Intrinsic	Normochromic	Normocytic	↑	↑	↓	Nl or moderately ↑	Nl	Nl	Nl or moderately ↑	↓	Nl	Increased erythropoiesis Howell-Jolly bodies Anisocytosis
HbC disease	Glutamic acid–to-lysine mutation in β-globin	Gallstone	Joint pains Increased risk of infections	Splenomegaly Cholelithiasis Avascular necrosis of the femoral head	+	Intrinsic	Normochromic	Normocytic	↑	↑	↓	Nl	Nl	Nl	Nl	↓	−	Hemoglobin crystals inside RBCs Target cells
Paroxysmal nocturnal hemoglobinuria	PIGA gene mutations Impaired synthesis of GPI anchor for decay-accelerating factor	Associated with aplastic anemia Thrombosis	Fatigue Chest pain Dyspnea on exertion Headache	Chronic hemolysis Hepatomegaly Ascites Papilledema Skin nodules	+	Intrinsic	Normochromic	Normocytic	↑	↑	↓	Nl	↓	Nl	↑	↓	−	NA
Hereditary spherocytosis	Mutations in Ankyrin, Band 3, Protein 4.2, and spectrin	Associated with parvovirus B19 Cholelithiasis Megaloblastic crisis	Aplastic crisis	Splenomegaly	+	Intrinsic	Normochromic	Normocytic	↑	↑	↓	Nl	↓	Nl	↑	Nl	−	Small, round RBCs with less surface area and no central pallor
Disease	Genetics	History	Symptoms	Signs	Hemolysis	Intrinsic/ Extrinsic	Hb concentration	MCV	RDW	Reticulocytosis	Haptoglobin levels	Hepcidin	Serum iron	Serum Tfr level	IBC	Ferritin	Transferrin saturation	Specific finding on blood smear
Microangiopathic hemolytic anemia	−	Associated with DIC TTP HUS SLE HELLP syndrome Hypertensive emergency	Purpura Confusion Aphasia Diplopia	Numbness of an arm or hand Jaundice Pale conjunctiva	+	Extrinsic	Normochromic	Normocytic	↑	↑	↓	Nl	↓	Nl	−	↑	−	Helmet cells
Macroangiopathic hemolytic anemia	Autoimmune	Associated with Prosthetic heart valves Aortic stenosis	Pallor Fatigue	Signs of anemia Complications of hemolysis Decreased vascular volume	+	Extrinsic	Normochromic	Normocytic	↑	↑	↓	Nl	↓	Nl	−	−	−	Spherocytes or schistocytes
Autoimmune hemolytic anemia	−	Associated with: SLE CLL Mycoplasma pneumonia	Painful blue fingers and toes on exposure to cold temperature Chest pain Chills Dizziness Tachycardia Headache Fatigue	Painful, blue fingers and toes with cold weather	+	Extrinsic	Normochromic	Normocytic	↑	↑	↓	Nl	↓	Nl	−	−	−	RBC agglutination
Aplastic anemia	Constitutive expression of Tbet Mutations in the perforin gene Mutations in SAP gene	Exposure to Radiation Drugs like Benzene, chloramphenicol, alkylating agents Viral infections like EBV, HIV, Hepatitis Fanconi anemia Idiopathic like Immune mediated, primary stem cell defect	Symptoms based on underlying condition	Short stature Cafe-au-lait spots Thumb defects Radial defects	−	−	Normochromic	Normocytic	↑	↓	Nl	Nl	↓	↓	Nl	↑	↓	Pancytopenia Fatty infiltration
Disease	Genetics	History	Symptoms	Signs	Hemolysis	Intrinsic/ Extrinsic	Hb concentration	MCV	RDW	Reticulocytosis	Haptoglobin levels	Hepcidin	Serum iron	Serum Tfr level	IBC	Ferritin	Transferrin saturation	Specific finding on blood smear
Folate deficiency	Impaired DNA synthesis	Alcohol consumption History of using drugs like methotrexate, trimethoprim, and phenytoin Low socioeconomic groups with poor nutrition Older people Pregnant and lactating women	No neurological symptoms vs B12 deficiency Odynophagia Angular stomatitis	Glossitis Signs of heart failure Anencephaly and spina bifida	−	−	Anisochromic	Macrocytic	↑	↓	Nl	Nl	↑	↑	↓	↑	↑	RBC macrocytosis Hypersegmented neutrophils Pancytopenia in severe cases
Vitamin B12 deficiency	Impaired DNA synthesis	Pernicious anemia Crohn's disease Gastrectomy Veganism Diphyllobothrium latum infection	Psychosis Insomnia Depression Cognitive slowing Restless leg syndrome	Neurological deficit Myelopathy Memory loss with reduced attention span Nystagmus Positive romberg sign Positive Lhermitte's sign	−	−	Anisochromic	Macrocytic	↑	↓	Nl	Nl	↑	↑	↓	↑	↑	Senile neutrophil Anisocytosis Ovalocytes
Orotic aciduria	Autosomal recessive Deficiency of enzyme UMPS	Episodic vomiting Rhabdomyolysis	Coma Gastrointestinal manifestation	Neurological manifestation	−	−	Anisochromic	Macrocytic	↑	↓	Nl	Nl	↑	↑	↓	↑	↑	NA
Fanconi anemia	Autosomal recessive X-linked recessive	History of anemia at age 16	Hypopigmentation Cafe-au-lait patches Radial ray anomaly	Significant for bilateral short thumbs	−	−	Anisochromic	Macrocytic	↑	↓	Nl	Nl	↑	↑	↓	↑	↑	Nl appearing WBC, RBC and Platelets But the number is greatly reduced
Disease	Genetics	History	Symptoms	Signs	Hemolysis	Intrinsic/ Extrinsic	Hb concentration	MCV	RDW	Reticulocytosis	Haptoglobin levels	Hepcidin	Serum iron	Serum Tfr level	IBC	Ferritin	Transferrin saturation	Specific finding on blood smear
Diamond-Blackfan anemia	Mutations in: RPL5 RPL11 RPL35A RPS7 RPS10 RPS17 RPS19 RPS24 RPS26	Associated with myelodysplastic syndrome Increased risk of AML	Pale skin Sleepiness Heart murmurs	Triphalangeal thumbs Short stature Microcephaly Hypertelorism Ptosis Micrognathia	−	−	Anisochromic	Macrocytic	Nl	↓	Nl	Nl	↑	↑	↓	↑	↑	NA
Infections	−	Associated with Malaria Babesia	Fever	Fever Signs of shock Headache	+	Extrinsic	Normochromic	Normocytic	↑	↑	↓	Nl	Nl	Nl	−	−	−	Trophozoite Maltese crosses
Chronic kidney disease	−	Pericarditis Encephalopathy Rectal incontinence Decreased libido Restless leg syndrome	Polyuria Hematuria Edema	Hypertension	−	−	Normochromic	Normocytic	↑	Nl/↑	Nl	↑	↓	−	↓	↑	↓	Nl
Liver disease	−	Hepatitis Binge drinking Gall bladder disease	Jaundice Abdominal pain Itchy skin	Ascites Right upper quadrant pain Hepatomegaly Swelling in the legs Ankle swelling	−	−	Anisochromic	Macrocytic	↑	↑	Nl	Nl	↑	↑	↓	↑	↑	Round macrocytes Target macrocytes
Alcoholism	−	History of increased alcohol intake Folic acid deficiency	Memory impairment Nausea Sweating	Truncal obesity Asterixis Encephalopathy Spider angiomas Hematemesis Gynecomastia	−	−	Anisochromic	Macrocytic	↑	↑	Nl	Nl	↑	↑	↓	↑	↑	Oval macrocytes Hypersegmented neutrophils
Disease	Genetics	History	Symptoms	Signs	Hemolysis	Intrinsic/ Extrinsic	Hb concentration	MCV	RDW	Reticulocytosis	Haptoglobin levels	Hepcidin	Serum iron	Serum Tfr level	IBC	Ferritin	Transferrin saturation	Specific finding on blood smear

Medical Therapy

If hemodynamic compromise is present, then immediate intervention is required which includes:

• Administration of O2 as needed
• Iron, folate, vitamin B12 supplements as necessary
• IV fluids for maintenance of blood pressure
• For hemoglobins <8 gm/dl, blood transfusions are indicated
• Establishment of two large-bore IVs for cases of ongoing acute blood loss

There are many different treatments for anemia and the treatment depends on severity and the cause.

Iron deficiency from nutritional causes is rare in non-menstruating adults (men and post-menopausal women). The diagnosis of iron deficiency mandates a search for potential sources of loss such as gastrointestinal bleeding from ulcers or colon cancer. Mild to moderate iron deficiency anemia is treated by iron supplementation with ferrous sulfate or ferrous gluconate. Vitamin C may aid in the body's ability to absorb iron.

Vitamin supplements given orally (folic acid) or subcutaneously (vitamin B-12) will replace specific deficiencies.

In anemia of chronic disease, anemia associated with chemotherapy, or anemia associated with renal disease, some clinicians prescribe recombinant erythropoietin, epoetin alfa, to stimulate red cell production.

In severe cases of anemia, or with ongoing blood loss, a blood transfusion may be necessary. Transfusions can be complication by circulatory overload and iron overload so much be used with caution.

Contraindicated medications

Severe anemia is considered an absolute contraindication to the use of the following medications:

• Methotrexate
• Nitroglycerin

Blood Transfusions

• Doctors attempt to avoid blood transfusion in general, since multiple lines of evidence point to increased adverse patient clinical outcomes with more intensive transfusion strategies. The physiological principle that reduction of oxygen delivery associated with anemia leads to adverse clinical outcomes is balanced by the finding that transfusion does not necessarily mitigate these adverse clinical outcomes.
• In severe, acute bleeding, transfusions of donated blood are often lifesaving. Improvements in battlefield casualty survival is attributable, at least in part, to the recent improvements in blood banking and transfusion techniques.
• Transfusion of the stable but anemic hospitalized patient has been the subject of numerous clinical trials, and transfusion is emerging as a deleterious intervention.
• Four randomized controlled clinical trials have been conducted to evaluate aggressive versus conservative transfusion strategies in critically ill patients. All four of these studies failed to find a benefit with more aggressive transfusion strategies.
• In addition, at least two retrospective studies have shown increases in adverse clinical outcomes with more aggressive transfusion strategies.
• On the whole, these studies suggest that aggressive transfusions, at least for hospitalized patients, may at best not improve any clinical parameter, and at worst lead to adverse outcomes.
• A recent report suggests that the culprit is the depletion of nitric oxide, an important vasodilator, in banked blood. The theory is that the transfusion of nitric oxide-depleted blood causes systemic vasoconstriction, and exacerbates hypoxia in tissues at risk.