Haemolysis Flashcards by Caitlin McMullen

Define Haemolysis

hola

Premature red cell destruction, can result in anaemia

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What causes warm autoimmune haemolysis?

(1) IgG autoantibodies

(2) idiopathic

(3) linked to SLE, CLL, drugs, and infections.

(4) Occurs at ≥ 37°C.

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What causes cold autoimmune haemolysis?

(1) IgM autoantibodies

(2) linked to infections (EBV, mycoplasma).

(3) Occurs at 0-10°C

(4) can angulate, cause holes in cell (MAC)

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What causes alloimmune haemolysis?

The immune system attacks transfused red blood cells

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What causes haemolytic transfusion reactions?

(1) Immediate (IgM) intravascular
(2) Delayed (IgG) extravascular

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What is the haemolytic disease of the newborn?

Due to Rh or ABO incompatibility, or anti-Kell antibodies

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What causes mechanical red cell destruction?

(1) DIC - Disseminated Intravascular Coagulation

(2) HUS - Hemolytic Uremic Syndrome

(3) TTP - Thrombotic Thrombocytopenic Purpura

(4) leaking heart valves
(5) malaria
(6) burns that physically damage red blood cells

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What causes hereditary spherocytosis?

A genetic defect causes RBCs to be sphere-shaped instead of biconcave.

= Results in jaundice, and splenomegaly, and can lead to aplastic crises due to parvovirus B19 infection

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What is G6PD deficiency?

X-linked condition causing hemolysis triggered by infection, drugs, or fava beans.

More common in Mediterranean/Middle Eastern populations

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Why are RBCs particularly susceptible to damage?

Biconcave shape, lack of nucleus, limited metabolic reserve

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What is compensated haemolysis?

Increased RBC destruction is matched by increased production, maintaining Hb levels

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What is decompensated haemolysis?

RBC destruction exceeds bone marrow production, leading to low Hb levels

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What are the consequences of haemolysis?

(1) Reticulocytosis
(2) Erythroid hyperplasia
(3) Excess bilirubin (jaundice, gallstones)

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What happens in extravascular haemolysis?

RBCs are destroyed by spleen/liver macrophages

= Leads to jaundice and splenomegaly

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What happens in intravascular haemolysis?

RBCs burst in circulation, releasing haemoglobin,

= Leads to hemoglobinemia and hemoglobinuria

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What are the clinical features of haemolysis?

jaundice, dark urine (hemoglobinuria), fatigue

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What tests confirm haemolysis?

(1) FBC
(2) Reticulocyte count
(3) Unconjugated bilirubin
(4) Blood film (spherocytes, Heinz bodies)
(5) Direct Coombs’ test

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What does raised lactate dehydrogenase (LDH) indicate?

It suggests red cell destruction

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How is haemolysis treated?

Corticosteroids for autoimmune

IV fluids for transfusion reactions

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The first-line treatment for warm autoimmune haemolytic anaemia is what?

steroids

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Second-line treatment for haemolysis is what?

Immunosuppressives and splenectomy

If the Coombs test was negative what disease does this rule out and why?

Autoimmune haemolytic anaemia

= Coombs test detects antibodies or complement on the surface of red blood cells. A negative Coombs test indicates that there are no antibodies or complement bound to the red blood cells, which rules out autoimmune hemolysis as the cause of anaemia

If no history of travel was mentioned. What haemolytic disease does this rule out?

Infection induced haemolytic anaemia

A 13-year-old girl of Middle Eastern origin is admitted with jaundice and shortness of breath on exertion. These symptoms have started over the course of the last day. She also complains of dark urine and denies any other symptoms. The patient has a past medical history of gallstones. No drug history or travel history is stated.

On examination, conjunctival pallor and jaundice are noted. She also has henna decorating both of her hands.
The Coomb test was negative. What is the underlying pathology giving rise to this presentation? and why?

G6PD haemolytic anaemia

= Given her ethnic origin and the fact that she has had henna tattooing which can trigger haemolytic crises in patients with G6PD, this is the most likely answer

A 35-year-old man with Glucose-6-phosphate deficiency (G6PD) wants to go on holiday to Nigeria. What medication should be avoided for malaria prophylaxis?

Primaquine

Heinz bodies and bite cells on the blood film suggest what

oxidative damage to red blood cells, which are common in conditions like G6PD deficiency

The patient’s history of neonatal jaundice may have been an early sign for what?

G6PD deficiency

A 59 year old woman is found to have features of extra-vascular haemolysis on investigation for fatigue; with a haemoglobin concentration of 88 g/L (normal range 115-150 g/L), unconjugated hyperbilirubinaemia of 46 mmol/L (normal <17), and splenomegaly on examination. The blood count is otherwise normal, and her blood film shows spherocytes and reticulocytosis, and no evidence of intracellular parasites or red cell fragments. There is no social, travel or family history of relevance. What is the single most appropriate next step?

Coombs' test (direct antigen test)

A 32-year-old male from northern Europe attends the GP for his annual influenza vaccine and 5-yearly pneumovax booster. He is new to the practice and informs the GP that he had a splenectomy when he was 4 years old for recurrent haemolytic episodes. He is unable to remember the name of the underlying disease. He also explains that there is a prominent family history of similar issues: his father, and two of his three daughters are affected, but his wife is unaffected. On examination, the GP notes a splenectomy scar, but no other findings. What is the single most likely underlying diagnosis?

Hereditary spherocytosis

What are the triggers for glucose-6-phosphatase (G6PD) deficiency?

(1) Intercurrent illness or infection (2) Fava beans (3) Henna (4) Medications: primaquine, sulfa-drugs (such as sulfamethoxazole), nitrofurantoin, quinolones, dapsone and NSAIDs/Aspirin

A 70-year-old male presents to the general practitioner complaining of a three-month history of his hands and feet changing colour to dark red. This only happens when he is exposed to cold temperatures and is painful. He also reports a gradual onset of increasing fatigue and breathlessness. His past medical history includes chronic lymphocytic leukaemia. Blood tests show haemoglobin 86 g/l (normal range 135-180g/l), reticulocytes 3.4% (normal range 0.5-1.5%) and a positive Coombs test. Given the likely diagnosis, which immunoglobulin is most likely involved? and explain why.

IgM Cold autoimmune haemolytic anaemia, which occurs at temperatures around 0-10 degrees, is caused by IgM autoantibodies IgG antibodies are seen in warm autoimmune haemolytic anaemia

What are the first line investigation of chronic lymphocytic leukaemia?

Flow cytometry of peripheral blood

A 33-year-old female presents to the GP with fatigue and dyspnoea on exertion. Investigations reveal a normocytic anaemia, reticulocytosis and positive Direct Antiglobulin Test (DAT). Her past medical history includes systemic lupus erythematosus and asthma. She regularly takes beclomethasone 200mcg BD inhaler and the oral contraceptive pill. What would accurately describe the mechanism of the likely diagnosis?

IgG-mediated extravascular haemolytic disease = given her history of systemic lupus erythematosus (SLE), warm autoimmune haemolytic anaemia is the most likely diagnosis

What are the causes of warm AIHA?

(1) SLE (2) Idiopathic (3) Lymphoproliferative neoplasms (eg. chronic lymphocytic leukaemia and lymphoma) (4) Drugs (methyldopa)

What are the causes of cold AIHA?

(1) Post-infectious (usually after Mycoplasma or EBV) (2) Idiopathic (3) Lymphoproliferative disorders

Describe the difference in treatment for warm and cold AIHA

Warm AIHA is managed with prednisolone or immunosuppression (e.g. AZT) and transfusions if severe whereas Cold AIHA treatment is mostly supportive, warmed blood is transfused if required and resistant cases may trial rituximab

Is schistocytes a feature in autoimmune haemolysis?

nope

Symptoms: fatigue, jaundice, and splenomegaly. What haemolytic disease does this suggest?

Hot AIHA

Decreased reticulocyte count in those with Haemolytic anaemia. Is this correct?

No, Haemolytic anaemia leads to increased reticulocyte count

What haemolytic disease are Heinz bodies and bite cells present and seen on blood film?

G6PD deficiency

Haemolytic uraemic syndrome (HUS) often is caused by what?

E. coli 0157

What haemolytic diseases show spherocytes and explain the difference

Hereditary spherocytosis: Negative Coombs test, positive EMA binding test. AIHA: Positive Coombs test (direct antiglobulin test)

What is the genetic inheritance pattern of hereditary spherocytosis?

Autosomal dominant

What Is Hereditary Haemolytic Anaemia?

Includes conditions like sickle cell disease, thalassemias, and hereditary spherocytosis, often caused by genetic mutations affecting RBC structure or function (eg, Defect in erythrocyte cell membrane)

Common triggers of DIC include what?

(1) sepsis, trauma, malignancy, and obstetric complications (2) bleeding, bruising at venepuncture sites, hypotension and tachycardia

What are the typical lab findings in DIC?

(1) Prolonged Prothrombin Time/ Activated Partial Thromboplastin Time (2) Thrombocytopenia (3) Low fibrinogen (4) Elevated D-dimer

What haemolytic disease would you find Schistocytes?

Microangiopathic haemolytic anaemias (MAHA) (eg) 1. Thrombotic thrombocytopenic purpura (TTP) 2. Haemolytic uraemic syndrome (HUS) 3. Disseminated intravascular coagulation (DIC

Describe the difference between spherocytes and schistocytes

(1) Spherocytes = Small, round, dense red blood cells with no central pallor; formed due to membrane loss (eg, in AIHA or hereditary spherocytosis) (2) Schistocytes = Irregular, fragmented red blood cells; formed due to mechanical damage (eg, in MAHA, TTP, or DIC)

What does haemolytic anaemia usually present with? - lab findings

(1) Normocytic (2) Elevated reticulocyte count (3) unconjugated hyperbilirubinaemia (4) Raised LDH

Extravascular haemolysis: What are the causes?

(1) Sickle cell, thalassaemia (2) Hereditary spherocytosis (3) Haemolytic disease of newborn (4) Warm autoimmune haemolytic anaemia

Intravascular haemolysis: What are the causes?

(1) Mismatched blood transfusion (2) G6PD deficiency (3) Red cell fragmentation: heart valves, TTP, DIC, HUS (4) Paroxysmal nocturnal haemoglobinuria (5) Cold autoimmune haemolytic anaemia

Bite and blister cells are typical of the blood film in ...

G6PD deficiency