PAROXYSMAL NOCTURNAL HEMOGLOBINURIA

A major advance in the management of PNH has been the development of a humanized monoclonal antibody, eculizumab, directed against the complement component C5.

By blocking the complement cascade downstream of C5, eculizumab abrogates complement-dependent intravascular hemolysis in all PNH patients.

In paroxysmal nocturnal hemoglobinuria, neutrophils express reduced leukocyte alkaline phosphatase, which is a GPI linked protein. This is because in PNH there is mutation of phosphatidylinositol glycan class A(PIGA). Mutation in PIGA result in impaired linkage of proteins with glycosyl phosphatidylinositol, thereby reducing its expression.

Ref: Harrison’s Principle of Internal Medicine, 18th Edition, Pages 883-884, Chapter 106 ; Diagnostic Pediatric Hematopathology By Maria A. Proytcheva, Page 86

Dyskeratosis congenita is associated with pancytopenia and hypocellular bone marrow.

Pancytopenia with hypercellular marrow is seen in:

• Myelodysplasia
• Myelofibrosis
• Hairy cell leukemia
• Tuberculosis
• Sarcoidosis
• Brucellosis
• PNH

• Q fever
• Legionnaires disease
• Anorexia nervosa, starvation
• Mycobacterium

Ans. is ‘a’ i.e., Increased LAP score

Clinical features of PNH

A. Intravascular hemolysis

*  The main feature of PNH is increased intravascular hemolysis that results in –

        Hemoglobinemia                                      Increased urine urobilinogen

        Hemoglobinuria                                         Decreased serum haptoglobin

        Hemosiderinuria                                        Increased serum LDH

             Increased serum bilirubin

• The hemolysis is paroxysmal and usually occurs in the night because during sleep the pH of blood gets slightly reduced and acidic medium leads to activation of the complement.

B. Thrombosis

• In PNH there is epsodic thrombosis due to absence of CD-59 on platelets, this results in externilization of phosphotidylserine, a site for prothrombinase complexes and thus increase the propensity for thrombosis.

*  Intrabdominal veins are the most common sites of thrombosis that may result in Budd chiary syndrome due to hepatic vein thrombosis.

C. Other features         

• Thrombocytopenia
• Granulocytopenia

*  Decreased LAP score

*   Normoblastic hyperplasia of bone marrow

*  PNH patients are also at increased risk for developing acute myelogenous leukemia and aplastic anemia.

Ans. is ‘c. Glycosylphosphatidylinositol 

o PNH results from acquired mutation that inhibits the synthesis of Glycosyl-phosphatidyl-inositol (GPI).

o The GPI linked proteins that are missing are membrane inhibitors of reactive lysis (MIRL; CD59), delay accelerating factor (DAF; CD55), C8 binding protein, urokinase plasminogen activator receptor, leukocyte alkaline phosphatase

(LAP).

Ans. is ‘d’ i.e., Congenital dyserythropoietic anemia

Pancytopenia refers to as decreased counts of all the three blood cells, i.e., RBC, WBC, and platelets. o Pancytopenia may have any of the two pathogenic mechanisms.

1.Decreased production of blood cells in bone marrow (more common) as in aplastic anemia.

2.Increased peripheral destruction of blood cells as in hypersplenism

Pancytopenia with Hvpocellular Bone marrow

o Acquired aplastic anemia

o Constitutional aplastic anemia (Fanconi’s anemia, dyskeratosis congenita)

• Some myelodysplasia

o Rare aleukemic leukemia (AML)

• Some acute lymphoid leukemia

o Some lymphomas of bone marrow

Ans. is ‘a’ i.e., AML; ‘b’ i.e., Myelodysplastic anemia; ‘c’ i.e., Paroxysmal nocturnal hemoglobinuria

Aplastic anemia can progress to : –

Paroxysmal nocturnal hemoglobinuria, Myelodysplastic anaemia, Rarely acute leukemia.

Ans. is ‘a’ i.e., Paroxysmal nocturnal hemoglobinuria

Ans is ‘d’ ie Sickle cell anemia 

Sickle cell anemia does not cause DVT. They cause vaso-occlusive crisis by plugging the microcirculation (aggregate of Sickle cell are formed in the capillaries because of hypoxia).

Answer is C (Thalassemia)

Hemoglobinopathies including thalassemia cause extravascular hemolysis and not intravascular hemolysis.

Causes of intravascular hemolysis

• Blood transfusion

– ABO mismatched transfusion – Infected blood

• Thermal burns
• Snake bites
• Sepsis

– Bacterial / parasitic infections – Clostridial sepsis

– Malaria

– Bartonellosis

– Mycoplasma pneumoniae

• Mechanical heart valves
• Paroxysmal hemoglobinuria – PNH

– PCH

Causes of extravascular hemolysis

• Blood and viral infections  – Malaria

–   Mycoplasma pneumoiae – Infectious mononucleosis

• Drug-induced hemolysis

– G6PD/GSH deficiency

– Autoimmune drug reactions – Strong oxidant drugs/chemicals

• Autoimmune hemolysis

– Warm-reacting (IgG) AIHA – Cold-reacting (IgM) AIHA

• Hemoglobinopathies

– Thalassemia

• Membrane structural defect  – Hereditary sperocytosis

– Hereditary spherocytosis – Acanthocytosis

• Environmental disorders
  – Malignancy/D1C

– TTP/HUS

The answer is D (Anemia in C.R.F.)

Anemia of chronic disease is associated with a normal/low Reticulocyte count.

Reticulocytes are young red cells with the presence of nuclear remnants in the cytoplasm. Their number gives an estimate of the adequacy of marrow response to anemia.

Reticulocyte count (Normal is 0.5 to 1.5% of all red cells):

High Reticulocyte Count                                                                     Low Reticulocyte Count

1. Hemolysis from any cause eg. Hemolytic anemias         1. Aplastic anemia including hereditary Spherocytosis & PNH.
2. Bleeding (Bloodloss)                                                             2. Nutritional deficiency anemia.

Answer is C (Increased alkaline phosphatase)

Conditions with decreased LAP scores

1. P.N.H.
2. C.M.L.

Conditions with increased LAP scores

1. Polycythemia (-)
2. Leukemoid reaction c.)
3. Infection

Answer is C (Paroxysmal Nocturnal hemoglobinuria)

Paroxysmal nocturnal hemoglobinuria (PNH) results from an acquired somatic mutation on the pluripotent stem cells. Hence all its clonal progeny i.e. red cells, white cells, and platelets are affected –
Paroxysmal nocturnal hemoglobinuria: is an acquired clonal disease that is associated with abnormality of complement regulation. This defect affects the Pluripotent stem cells & the clonal progeny of these stem cells. Red cells, white cells & platelets thus all are affected.

Paroxysmal cold hemoglobinuria, Black fan Diamond syndrome (pure red cell aplasia), and hemolytic anemias characteristically involve the red cell lineage only.

Answer is C (Decreased LDH)

Because of increased activation of complement and complement mediated destruction of RBC there occurs intravascular hemolysis and an elevated LDH is seen.

Paroxysmal nocturnal haemoglobinuria may have thrombosis and thrombocytopenia both, as is depicted in the previous explanations.

Answer is C (Dyskeratosis Congenita )

Dyskeratosis congenita (constitutional aplastic anemia) is associated with Pancytopenia and a Hypocellular bone marrow

Myelodysplasia, PNH and Sarcoidosis may all be associated with Pancytopenia and a cellular bone marrow

Answer is A (Fanconi’s Anemia)

Constitutional Aplastic Anemias like Fanconi’s Anemia are associated with a Thpoplastic Marrow

Myelofibrosis, Paroxysmal Nocturnal Hemoglobinuria (PNH) and Hypersplenism are all associated with a cellular marrow.

Answer is D (G-6PD Deficiency)

Glucose – 6 – PD Deficiency is not associated with Pancytopenia and a cellular marrow

Myelodysplasias, PNH and Megaloblastic anemia (Vit B₁₂,Folate deficiency) may present with Pancytopenia and a cellular marrow.

Answer is C (Idiopathic Thrombocytopenic Purpura (ITP))

Idiopathic Thrombocytopenic Purpura (ITP) is an immune complex mediated thrombocytopenia characterized by varying degrees of bleeding manifestations due to destruction of platelets. 1TP is not associated with an increased incidence of venous and/or arterial thrombosis.

Paroxysmal Nocturnal Haemoglobinuria (PNH), Diseminated Intravascular Coagulation (DIC) and Heparin Induced Thrombocytopenia (HIT) are all associated with increased risk of venous and/or arterial thrombotic events.

Risk factors for Thrombosis:

Note : Heparin induced Thrombocytopenia is more commonly associated with Thrombosis than Bleeding

Heparin induced Thrombocytopenia is more commonly associated with Thrombosis than Bleeding

• Heparin induced thrombocytopenia should be included in the differential diagnosis of conditions that produce thrombosis despite thrombocytopenia.
• Despite thrombocytopenia bleeding is rare in HIT.

On the contrary HIT is more related to thrombosis, which often leads to initial recognition of this condition (HIT).

`Thrombosis often leads to initial recognition of HIT. Bleeding is rare despite thrombocytopenia’

– Essentials of Emergency Medicine (2006)/286

Thrombocytopenia with Thrombosis

DIC TTP HUS HIT

Thrombosis in Heparin Induced Thrombocytopenia is caused by the generation of prothrombotic platelet microparticles that promote thrombin generation.

HIT is an antibody – mediated process that is triggered by antibodies directed against neoantigens on PF4 that are exposed when heparin binds to this protein. These antibodies (usually IgG type) bind simultaneously to heparin PF4 complex and to platelet Fc receptors. Such binding activates the platelets and generates platelet microparticles. Circulating microparticles are prothrombotic because they express anionic phospholipids on their surface and can bind clotting factors and promote thrombin generation.

Features of Heparin-Induced Thrombocytopenia

Features                                                 Details

Thrombocytopenia                           Platelet count of <100,000/,uL or a decrease in platelet count > 50%

Timing                                         Platelet count falls 5-10 days after starting heparin

Type of heparin                             More common with unfractionated heparin than with low-molecular-weight heparin

Type of patient                             More common in surgical patients than medical patients; more common in women than in men.

Thrombosis                                  Venous thrombosis more common than arterial thrombosis

Answer is C (Hypomagnesemia):

All conditions other than hypmagnesemia are known predisposing causes of thrombosis.

Answer is A (Diabetes Mellitus)

Diabetes Mellitus has not been mentioned as a risk factor for deep venous thrombosis.

Prolonged surgery and OCP usage are established risk factors.

PNH is associated with hypercoagulability (CMDT 2008) and an increased risk of deep venous thrombosis.

Answer is C (Paroxymal nocturnal hemoglobinuria)

P’sH is the most common cause of iSudd Chiral syndrome amongst the options provided.

• Most common cause of Budd chiari syndrome is – thrombosis of hepatic vein^Q

This is seen in the setting of : – polycythemia rubra vera^Q

– myeloproliferative syndrome^Q

–  Paroxysmal nocturnal hemoglobinuriaQ

–  Oral contraceptive use

–  Hyercoagulable states

• It may also result from obstruction of venacava.^Q

This may be seen in the setting of :

– invasion of IVC by tumor such as hepatocellular carcinoma.

– Idiopathetic membranous obstruction of IVC is the most common cause of this syndrome in Japan.

Answer is B (Paroxysmal Cold Haemoglobinuria (PCH))

Paroxysmal Cold Hemoglobinuria (PCH) is a benign self-limiting autoimmune hemolytic anemia. PCH does not undergo leukemic transformation and is hence not considered a Preleukemic condition. Recovery is the rule in Paroxysmal Cold Hemoglobinuria.

Paroxysmal Nocturnal Haemoglobinuria may be considered a Preleukemic condition

PNH may evolve into Aplastic anemia and PNH may manifest itself in patients who previously have Aplastic Anemia. Rarely (estimated 1-2% (Ian cases) PNH may terminate in Acute Myeloid Leukemia’. – Harrison 18th/883

Myelodysplasia (Myelodysplastic Syndrome) is a Preleukemic condition

Ans. is ‘d’ i.e., Hereditary spherocytosis

• Blood transfusion
• ABO mismatched transfusion
•  Infected blood
• Thermal burns
• Snake bites
• Sepsis
• Bacterial/parasitic infections
• Clostridial sepsis
• Malaria
• Bartonellosis
• Mycoplasma pneumoniae
• Mechanical heart valves
• Paroxysmal hemoglobinuria
• PNH
• PCH