17.4 Pathology

• Introduction
  
• Hemoglobinopathies
  • Quantitative hemoglobinopathies (thalassemias)
  • Structural hemoglobinopathies (sickle cell syndrome)
• Myelopathies
  • Panmyelopathies
• Blood clotting disorders
  • Thrombocytopenias
  • Hereditary coagulopathies
• Disorders of the lymph vessels
• Immunologic disorders
  • Catch22
  • Myasthenia gravis

Introduction

It is impossible within the scope of the material presented here to take up all of the possible disorders of the blood and the lymph-associated organs. Here the disorders that are the most relevant will be treated.

Hemoglobinopathies

Hemoglobinopathies are congenital disorders of the hemoglobin synthesis as a result of various genetic defects in the formation of the a or b chains.

Quantitative hemoglobinopathies (thalassemias)

Thalassemias are a group of autosomal-recessive hereditary diseases in which the synthesis of a globin chain is affected. In a disorder of the b chain synthesis a b-thalassemia is present while if the a chain is affected, this is termed an a-thalassemia. Thalassemias are mostly due to a mutation of the regulatory DNA sequence (LCR).
Also see: Hemoglobin

Structural hemoglobinopathies (sickle cell syndrome)

The congenital structural changes of individual hemoglobin chains are due to a mutation of the corresponding genes. The most frequent hemoglobinopathy is the homozygous form of sickle cell anemia (Hb-SS disease). It arises due to a mutation of the b globin gene on chromosome 11p15.4. This results in an exchange of glutamine acid and valine at position 6 of the b chain. When the oxygen concentration is low, the HbS changes its 3D configuration and forms aggregates that lead to a sickle shape of the erythrocytes. These rigid erythrocytes become especially sequestered in the spleen and can, in addition, lead to vessel blockages.
Also see: Spleen diagram with open and closed circulation