RBC disorders 2 Flashcards
Causes of Normocytic anemiascorrected reticulocyte count <3%
Acute blood loss Early iron deficiency and ACD Aplastic anemia Chronic renal failure malignancy
normocytic anemia intrinsic defects
Membrane defect
Abnormal Hb
Enzyme deficiency
normocytic anemia extrinsic defects
Trauma (e.g. aortic stenosis, prosthetic valves)
Immune destruction
Mechanism and labs for normocytic extravascular hemolysis
Rbc phagocytosis by splenic and hepatic macs
Igg bound, with or without c3b
Abnormal shape (e.g. spherocytosis, sickling)
Laboratory findings:
Increase unconjugated bilirubin
Increased serum LDH
Mechanism and labs for normocytic intravascular hemolysis
intravascular hemolysis Rbc phagocytosis by splenic and hepatic macs Hemolysis occurs within blood vessels Enzyme deficiency (g6pd) Mechanical trauma Complement/immune destruction
Laboratory findings: Increase unconjugated bilirubin (minimal) Increased serum LDH Decreased serum haptoglobin hemosiderinuria
Basic hereditary spherocytosis points
Autosomal dominant USA 1/5,000 Intrinsic defect . . . Where would the hemolysis occur? Mutations in ankyrin most common Band 3, spectrins, protein 4.2
hereditary spherocytosis clinical features
Clinical features Jaundice Gallstones Splenomegaly Aplastic crisis in children
Hereditary spherocytosis lab findings
Laboratory findings Normocytic anemia Increased MCHC Increased osmotic fragility (rupture in hypotonic solution) Elevated LDH and bili
Not all spherocytes are due to genetic disease
Warm autoimmune hemolytic anemia, ABO incompatibility, etc
Hereditary elliptocytosis
Autosomal dominant
Defect in spectrin tetramers or 4.1
Mild anemia
splenomegaly
Sickle cell anemia basic features
Autosomal recessive missense mutation
Valine substitution for glutamic acid in beta-globin chain
Heterozygote (HbAs) – 10% of blacks – no anemia
Hbss anemia (60% Hbs is threshold for disease)
Predominantly extravascular hemolysis Hbs molecules aggregate. Triggers: low ph low oxygen tension Volume depletion
sickle cell clinical findings
Clinical findings: Dactylitis Acute chest syndrome (most common cause of death) Stroke Gallstones priapism Aseptic necrosis of femoral head Aplastic crisis (ass. With parvovirus) Autosplenectomy (splenomegaly by 2 yo, then loses function) – Howell-jolly bodies
three complications of sickle cell
Susceptibility to infections:
due to dysfunctional spleen
Strep pneumonia, other encapsulated organisms
Osteomyelitis by salmonella paratyphi
renal findings with sickle cell
Sickle may occur in peritubular capillaries
Microhematuria
Renal papillary necrosis
sickle cell treatment
Treatment:
Infectious prophylaxis
Pain management
Transfusion – acute chest syndrome, aplastic crisis
Preventive measures: Hydroxyurea Immunizations Pneumococcal vaccine Folic acid supplementation
G6PD deficiency basic features
recessive X--linked pattern affects 22% of U.S. blacks females are asymptomatic older RBCs usually affected young RBCs have normal or near normal levels > 100,000,000 worldwide over 100 genetic variants known most represent amino acid substitutions
G6PD deficiency pathophysiology
Pathophysiology Glutathione (reduced state) protects RBCs and their membranes from oxidants Oxidative Damage → hemolysis Inciting causes: Infection Drugs: primaquine, sulfas, Other compounds – in fava beans, etc.
G6PD Mediterranean
↓ enzyme activity throughout life span of RBCs
drug + Hb → production of H2O2
accumulating H2O2 injures RBC → hemolysis
Oxidized hemoglobin precipitates (Heinz bodies)
“bite cells” – macrophage removal of damaged membrane
more severe
G6PD deficiency clinical and lab findings
Clinical and laboratory findings:
sudden onset back pain and delayed hemoglobinuria
Susceptibility to infections (impaired MPO – no nadph)
normocytic anemia
Heinz bodies
RBC enzyme analysis after hemolytic episode has resolved
*g6pd levels are ~normal in retic and young cells
Immunohemolytic anemia basic features
Extrinsic hemolytic anemia with intra- or extravascular hemolysis
Warm agglutinins Cold agglutinins complement Drug induced Paroxysmal Cold Hemoglobinuria (PCH)
Immunohemolytic warm agglutinin
Most common hemolytic anemia - extravascular.
Igg-coated rbc’s are phagocytosed by splenic macrophages
~ 50% idiopathic
associated with SLE, collagen vascular diseases (SLE), CLL, malignant lymphoma (esp. Hodgkin’s), viral infections, etc.
Immunohemolytic cold agglutinin
intra- or extravascular hemolysis
causes include: Mycoplasma pneumoniae, infectious mononucleosis, CLL, drugs, etc.
Raynaud’s phenomenon common
immunohemolytic compliment mediated hemolysis
C3b coated rbc are phagocytosed by liver macs – extravascular
Rbc’s coated by c5-c9 membrane attack complex – intravascular
Immunohemolytic lab finding and clinical presentation
Jaundice
Hepatosplenomegaly
Raynaud’s phenomenon
Positive dat Positive indirect Unconjugated hyperbilirubinemia Hemoglobinuria Decreased haptoglobin Normocytic anemia Rbc agglutination (igm)
drug induced hemolytic anemia
Antibody (IgG) to drug binds to RBC membrane prototype is penicillin extravascular hemolysis direct coombs positive “innocent bystander”
Drug–anti-drug immune complex IgG or IgM bind complement IgG → extravascular hemolysis IgM → intravascular hemolysis drugs: quinidine, quinine, INH, sulfonamides
