Riassunto esame Pneumologia, prof. Centanni, libro consigliato Lymphadenitis and Splenomegaly, Robbins

Splenomegaly and lymphadenitis

Spleen

The spleen is a filter for the blood and a site of immune responses to blood-borne antigens.

Anatomy and histology

Normally located in the LUQ, its weight is 150 g, it is enclosed in a thin gray connective tissue capsule. Red pulp with dotted white pulp follicles are present. Germinal centers are identical to those seen in lymph nodes. The lining endothelium is discontinuous, providing a passage for blood cells between sinusoids and cords. Cords contain a labyrinth of macrophages serving to create a physical and functional filter.

Physiology

• Phagocytosis of blood cells and particulate matter: red cells become trapped in the cords getting more readily phagocytosed by macrophages.
• Ab production: dendritic cells trap Ag presenting them to T cells → T- and B-cell interaction leads to the generation of Ab-secreting PCs (spleen is also an important source of Ab directed against plt, like in immune thrombocytopenia purpura).
• Hematopoiesis: normally, splenic hematopoiesis stops at birth but can be reactivated in severe anemia.
• Sequestration of formed blood elements:
  • 30-40 mL of RBCs
  • 30-40% of platelets normally → 80-90% with splenomegaly → thrombocytopenia
  • WBCs trapping → leukopenia
• Largest unit of the mononuclear phagocyte system → involved in all systemic inflammations, generalized hematopoietic disorders, and many metabolic disturbances.

Splenomegaly

Clinical S&S: dragging sensation in the LUQ, pressure on the stomach, discomfort at eating, hypersplenism characterized by pancytopenia probably due to sequestration of blood formed elements.

Hematologic disorders associated to splenomegaly

• HL
• NHL
• MM
• Myeloproliferative disorders
• Hemolytic anemia

Neoplasms

Very rare except in myeloid and lymphoid tumors which often cause splenomegaly.

Myeloid metaplasia

Syndrome characterized by myeloid tissue in extramedullary sites with nucleated erythrocytes and immature granulocytes in the circulating blood and extramedullary hematopoiesis in the liver and spleen, as well as anemia and splenomegaly. Both a primary form (agnogenic myeloid m.) and forms secondary to carcinoma, leukemia, leukoerythroblastosis, and tuberculosis are known. Presenza di tessuto mieloide in sede extramidollare, che nello specifico (mielofibrosi) si realizza a livello splenico ed epatico [cit. Onida's mail].