Page 360 - Concise Pathology for Exam Preparation ( PDFDrive )

12 Haematology 345

Q. Enumerate the common causes of splenomegaly.

Ans. Causes of splenomegaly
• Mild splenomegaly (weight less than 500 g): Acute splenitis, acute splenic congestion,
enteric fever, infectious mononucleosis, brucellosis, septicaemia, SLE, infective endocar-
ditis, syphilis and parasitic infestations, eg, malaria, kala-azar.
• Moderate splenomegaly (weight 500–1000 g): Lymphomas, portal hypertension, acute
leukaemias, chronic lymphocytic leukaemia, chronic myeloid leukaemia, haemolytic
anaemias (hereditary spherocytosis and thalassaemia major), amyloidosis, Niemann–
Pick disease, tuberculosis, sarcoidosis, typhoid, metastatic carcinoma and sarcoma.
• Massive splenomegaly (weight more than 1000 g): Chronic myeloid leukaemia, my-
elofibrosis, hairy cell leukaemia, tropical splenomegaly, kala-azar, portal hypertension,
Gaucher disease, lymphomas, cysts and tumours of spleen.

Q. Write briefly on tropical splenomegaly.
Ans. Seen in residents of malaria endemic areas.
• Presents with low-grade fever and massive hepatosplenomegaly
• High levels of antimalarial antibodies are found in the blood. IgM levels are markedly raised.

Q. Write briefly on hypersplenism.
Ans. This is a term used to indicate anaemia, leucopenia and thrombocytopenia associ-
ated with prominent splenomegaly and a normal or hypercellular bone marrow (enlarged
spleen removes excessive numbers of the formed elements of blood). Leucopenia and
thrombocytopenia result from excessive sequestration of these cells in the large spleen.
Anaemia is believed to be dilutional, resulting from an increase in total plasma volume.

Common Causes
• Primary hypersplenism: No detectable cause
• Secondary hypersplenism: Portal hypertension, malaria, kala-azar; topical splenomegaly
syndrome and myeloproliferative disorders

Q. Write briefly on the mechanism of haemostasis.

Ans. There are three major components of the normal haemostatic mechanism:
1. Vascular component: This involves a reflex spasm of the injured vessel (vasoconstric-
tion), which serves to minimize the blood loss.
2. Platelet component
(a) Platelets are derived from marrow megakaryocytes. They are anucleate and have a
discoid shape. The normal lifespan is about 10 days. About 70% of the platelets are
in circulation while 30% are in the spleen.
(b) The cytoplasm of platelets contains three major types of storage granules:
(i) Alpha granules containing a variety of proteins like fibrinogen and von Will-
ebrand factor
(ii) Dense granules containing serotonin, ADP and calcium
(iii) Lysosomal granules containing acid hydrolases
Following vessel constriction, platelets adhere to the vessel wall. This is facilitated by:
• Factor VIII/von Willebrand factor released from damaged endothelial cells
• Exposed subendothelial collagen
• Release of ADP and thromboxane A 2
• Platelet activation results in the discharge of the granule contents and formation of
thromboxane A 2 from arachidonic acid, by the action of cyclooxygenase and throm-
boxane synthetase. Thromboxane A 2 is a potent stimulant of platelet aggregation.
• Platelet adhesion and platelet aggregation serve to form a platelet plug which seals off
the vascular breach and arrests haemorrhage.

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