Page 349 - Textbook of Pathology, 6th Edition

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CHAPTER 13

Figure 13.6 Laboratory findings of ITP contrasted with those found
in a normal individual. A, Peripheral blood in ITP shows presence of
reduced number of platelets which are often large. B, Bone marrow in
ITP shows characteristically increased number of megakaryocytes with
single non-lobulated nuclei and reduced cytoplasmic granularity (inbox
on right photomicrograph).

is explained by formation of anti-platelet autoantibodies, LABORATORY FINDINGS. The diagnosis of ITP can be Disorders of Platelets, Bleeding Disorders and Basic Transfusion Medicine
usually by platelet-associated IgG humoral antibodies suspected on clinical features after excluding the known
synthesised mainly in the spleen. These antibodies are causes of thrombocytopenia and is supported by the
directed against target antigens on the platelet glycoproteins, following haematologic findings:
Gp IIb-IIIa and Gp Ib-IX complex. Some of the antibodies 1. Platelet count is markedly reduced, usually in the range
directed against platelet surface also interfere in their of 10,000-50,000/μl.
function. The mechanism of platelet destruction is similar to
that seen in autoimmune haemolytic anaemias. Sensitised 2. Blood film shows only occasional platelets which are
platelets are destroyed mainly in the spleen and rendered often large in size (Fig. 13.6,A).
susceptible to phagocytosis by cells of the reticuloendothelial 3. Bone marrow shows increased number of mega-
system. karyocytes which have large non-lobulated single nuclei
and may have reduced cytoplasmic granularity and
CLINICAL FEATURES. The clinical manifestation of ITP presence of vacuoles (Fig. 13.6, B).
may develop abruptly in cases of acute ITP, or the onset may 4. With sensitive techniques, anti-platelet IgG antibody can
be insidious as occurs in majority of cases of chronic ITP. be demonstrated on platelet surface or in the serum of
The usual manifestations are petechial haemorrhages, easy patients.
bruising, and mucosal bleeding such as menorrhagia in 5. Platelet survival studies reveal markedly reduced platelet
women, nasal bleeding, bleeding from gums, melaena and lifespan, sometimes less than one hour, as compared with
haematuria. Intracranial haemorrhage is, however, rare. normal lifespan of 7-10 days.
Splenomegaly and hepatomegaly may occur in cases with
chronic ITP but lymphadenopathy is quite uncommon in TREATMENT. Spontaneous recovery occurs in 90% cases
either type of ITP. of acute ITP, while only less than 10% cases of chronic ITP