Pathogenesis & Lab Diagnosis

of

Sickle Cell Anemia & Thalassemia

Pathogenesis

Of

Hemolytic Anemia

Intravascular Extravascular

Abnormal

RBCs

Destruction at

Splenic sinusoids

Release of

hemoglobin Hb transported

Fate of Hemoglobin

Porphyrin portion of Heme - Bilirubin

Iron portion of Heme – Bone Marrow stores

Globin – Amino acids recycled

Reduced RBC number

Rebound erythropoiesis

Ineffective Erythropoiesis Extra Medullary Erythropoiesis

Pathogenesis

Of

Hemolytic Anemia

Intravascular Extravascular

Abnormal

RBCs

Destruction at

Splenic sinusoids

Release of

hemoglobin

Peripheral Smear

RBC count

Hb%Decreased

Haptoglobin levels

Hb transported

Fate of Hemoglobin

Porphyrin portion of Heme - Bilirubin

Iron portion of Heme – Bone Marrow stores

Globin – Amino acids recycled

Reduced RBC number

Rebound erythropoiesis

Ineffective Erythropoiesis Extra Medullary Erythropoiesis

S. Bilirubin

S. Iron

Hepato splenomegaly

Crew hair cut appearance

BM – M:E ratio reversed

Reticulocyte count

Pathogenesis

Of

Hemolytic Anemia

Intravascular Extravascular

Abnormal

RBCs

Destruction at

Splenic sinusoids

Release of

hemoglobin Hb transported

?

Abnormal RBCs

Abnormal membrane : Hereditary Spherocytosis

Abnormal Enzymes : G6PD deficiency

Abnormal Hemoglobin

Deficiency

Thalassemia

Heme

MethemoglobinemiaAltered

Sickle Cell Disease

Globin

Pathophysiology of Sickle Cell Disease

Robbins & Cotran’s Pathological Basis of Disease

Abnormal RBCs

Abnormal membrane : Hereditary Spherocytosis

Abnormal Enzymes : G6PD deficiency

Abnormal Hemoglobin

Deficiency

Thalassemia

Heme

MethemoglobinemiaAltered

Sickle Cell Disease

Globin

Hb Electrophoresis

HPLC

Hb F levels

Electrophoretic pattern of Sickle Cell Disease

PJ Russell, iGenetics 3rd ed

Functional Assays for sickling

Sickling test:

2% Sodium Metabisulphite reduces oxygen

tension

Induces sickling.

Solubility test:

HbS precipitates in high molarity phosphate

(2.24M) buffer – due to reduced state.

Pathophysiology of Thalassemia

Inclusion bodies : β4 inclusion body

Heinz bodies: denatured hemoglobin

Howell Jolly bodies: DNA inclusion body

Robbins & Cotran’s Pathological Basis of Disease

Electrophoretic pattern of Thalassemia

NESTROFT

A screening test for β Thalassemia trait.

Reduced Osmotic Fragility of RBCs.

Normal Osmotic Fragility 0.5 to 0.32%

Negative Positive

DW 0.36% Saline DW 0.36% Saline

Piplani et al., Journal of Clinical and Diagnostic Research, August 2014

A word on

Prenatal Diagnosis & Neonatal screening

Summary

RBC indices Normal Male Normal female Β Thalassemia

major

Β Thalassemia

trait

Mean

corpuscular

volume (MCV

fl)

89.1±5.01 87.6±5.5 50-70 <79

Mean

corpuscular

hemoglobin

(MCH pg)

30.9±1.9 30.2±2.1 12-20 <27

Hemoglobin

(Hb g/dL)15.9±1.0 14.0±0.9 <7

Males: 11.5-

15.3

Females: 9.1-

14

Galanello R et al., Hemoglobin. 1979

Peripheral Smear: Sickle cells – SCD

Target cells, Heinz bodies, Inclusion bodies - Thalassemia

Hb Electrophoresis

Hb variants – Hb F in SCD & Thalassemia major

Hb A2 in Thalassemia minor

Sickling tests.

Genetic Mutational Analysis.

Thank You!