HAEMOTOLOGY I ; *2

Hypochromic Microcytic Anemia

• Characterized by smaller-than-usual RBCs (microcytic) with decreased red color (hypochromic).
• Most commonly caused by decreased iron reserves due to:
  • Decreased iron in diet
  • Poor iron absorption
  • Acute or chronic blood loss
  • Increased iron demand (pregnancy, trauma recovery)

Thalassaemia

• A genetic disorder which can result in significant morbidity and mortality.
• Can be either normocytic or microcytic anaemia.
• Two main groups:
  • Alpha-Thalassaemia (alpha chain defect)
  • Beta-Thalassaemia (beta chain defect)
• In both types:
  • Excess chains precipitate in red cell precursors, causing premature death.
  • Precipitated chains cause oxidative damage to the cell membrane, leading to haemolysis.
• Diagnosed via Hb electrophoresis.

Alpha Thalassaemia

• Involves 4 alpha-globin genes on 2 chromosomes.
• Four types:
  • Alpha plus-thalassaemia trait (deletion of 1 gene): asymptomatic with normal Hb and reduced MCV
  • Alpha (0) thalassaemia trait (deletion of 2 genes on 1 chromosome): slight reduction in Hb and reduced MCV
  • Hb H disease (deletion of 3 genes): chronic haemolytic anaemia, usually transfusion independent
  • Hb Bart’s hydrops fetalis syndrome (deletion of all 4 genes): intrauterine or neonatal death.

Beta Thalassaemia

• Two types:
  • Heterozygous beta-thalassaemia (trait): asymptomatic
  • Homozygous beta-thalassaemia: moderate to marked anaemia developing within the first 2 years.
• Usually due to mutation rather than deletion affecting the Beta gene.

Clinical Classifications of Thalassaemia

• Thalassaemia minima: presence of mutation without clinical consequence
• Thalassaemia minor: microcytosis and hypochromic red cells
• Thalassaemia intermedia: microcytic hypochromic anaemia, extramedullary haematopoiesis with splenomegaly
• Thalassaemia major: severe anaemia and transfusion dependent, including features above

Untreated Thalassaemia

• Leads to:
  • Growth retardation
  • Splenomegaly
  • Bony deformities due to marrow expansion

Oral Clinical Features of Thalassaemia

• Enlarged Maxilla (chipmunk facies)
• Gap in the middle of the tooth (migration and spacing of anterior teeth)
• Chicken wire alv bone
• Swelling of parotids
• Xerostomia
• BMS
• Oral Ulcerations

Thalassaemia Treatment

• Main concern is iron overload.
• Transfusions lead to iron accumulation in the:
  • Myocardium (cardiac failure)
  • Liver (cirrhosis)
  • Pancreas (DM)
  • Salivary glands

Sickle Cell Anaemia

• The most common structural variant is HbS.
• Caused by mutation in the beta-globin gene.
• Interaction of sickle beta-globin chains with normal alpha-globin chains results in HbS.
• Leads to deformation of the cell into a sickle shape.
• Sickle trait occurs in heterozygotes (20-40% HbS, remaining HbA).
• Sickle cell anaemia occurs in homozygotes (100% HbS).

Clinical Manifestations of Sickle Cell Anaemia

• Chronic haemolytic anaemia (60-90 g/L)
• Hyposplenism (due to infarcts increased risk of infection)
• Splenic sequestration
• Acute chest syndrome
• CVA/TIA
• Bone infarction and subsequent infections
• Chronic leg ulcers
• Haematuria and renal disease

Sickle Cell Anaemia Pathophysiology

• Sickling results in:
  • Shortened erythrocyte survival.
  • Microcirculation obstruction.

Management of Sickle Cell Anaemia

• Diagnosis via Hb electrophoresis
• Transfusion when necessary
• Pneumococcal, Hib, and meningococcal vaccinations
• Prophylactic penicillin

Sickle Cell Crises

• Acute vaso-occlusive painful episodes precipitated by infection, dehydration, hypoxia.
• Treatment:
  • Oral and IV fluids
  • Analgesics (opiates)

Transfusion Reactions

• Caused by variation in surface constituents of red cells.

ABO System

• Denotes presence of A and B antigens on erythrocytes
• Involves the H antigen.
• A: presence of the A allele leads to H antigen modification
• B: presence of the B allele leads to H antigen modification
• O: encodes for no modification
• Six possible genotypes: AA, AB, AO, BB, BO, OO
• Four phenotypes:
  • A: can receive A or O
  • AB: can receive A, B, or O
  • B: can receive B or O
  • O: can only receive O

Rh System

• Rhesus (Rh) factor is an inherited protein found on the surface of red blood cells.
• If your blood has the protein, you're Rh positive.
• If your blood lacks the protein, you're Rh negative.
• Used mainly on pregnant women
• Involves the D antigen.
• Rh protein encoded by 2 genetic loci on 1 chromosome.
• RhD-negative person is at significant risk of developing anti-D antibodies after transfusion of RhD-positive blood.
• Pregnant women are tested for RhD; if RhD negative, they are treated with antenatal anti-D prophylaxis if their fetus may be RhD positive.

Immune-Mediated Transfusion Reactions

• Two classifications:
  • Acute reactions: occur within 24 hours of transfusion (acute haemolytic, febrile non-haemolytic, allergic, transfusion-related acute lung injury).
  • Delayed reactions: occur days to weeks after transfusion (delayed haemolytic transfusion reactions, transfusion-associated graft-versus-host disease, post-transfusion purpura).
• 10% mortality rate.
• Clinical features:
  • Fever
  • Agitation/anxiety
  • Rigor
  • Rash
  • Flushing and sweating
  • Chest/abdominal pain
  • Profound hypotension
  • Bleeding
  • Diarrhoea

Management of Immune-Mediated Transfusion Reactions

• Stop transfusion
• Check patient identity against donor blood product unit
• Replace giving set
• Administer paracetamol and IV fluids
• Use IM adrenaline if anaphylaxis is suspected
• Contact haematology

Dental Considerations for Anaemia

• Patients may present with oral features suggestive of anaemia
• Anemia may complicate treatment
• It may be sensible to delay treatment if there is no clear explanation

Oral Features Associated with Haematinic Deficiencies

• Angular cheilitis
• Glossitis
• Oral ulceration
• Peripheral neuropathies

Oral Features Associated with Sickle Cell Anaemia

• Oral pain due to infarction
• Osteomyelitis
• Trigeminal neuropathy (Due to osteomyelitis)
• Hypomineralised dentition

Radiographic Features Indicating Anaemia

• Dense lamina dura
• Hypercementosis
• Radio-opacities due to previous infarcts

Potential Issues with Dental Treatment in Anaemic Patients

• Bleeding risk
  • Bone marrow infiltration may cause failure of platelet production.
  • Liver disease may impact clotting factor synthesis
• Anaesthesia
  • Avoid prilocaine (methaemoglobinaemia risk).
  • Thalassaemia and sickle cell anaemia can complicate procedures performed under GA.