Thrombocytopenia

It is a platelets count less than 150 ×109/L. It is classified according to the nature of defect into:

  1. Impaired production.
  2. Peripheral destruction.
  3. Abnormal distribution.

Impaired platelets production

  1. Hypoplasia: aplastic anemia, idiopathic megakaryocytic hypoplasia and drug induced megakaryocytic hypoplasia.
  2. Bone marrow infiltration: TB, leukemia, lymphoma and secondary metastasis. They suppress megakaryocytes.
  3. Metabolic defect related to megakaryocytes: B12 or folate deficiency, alcoholism and cytotoxic drugs.
  4. Congenital defect of platelets: Thrombocytopenia with absent radius (TAR), Wiskott megakaryocytes defect and may-Hegglin disease (abnormal leukocytes and thrombocytopenia).
  5. Viral infection: suppress megakaryocytes.

Peripheral platelets destruction

Immune:

  • Auto-immune:
  • Auto-immune idiopathic thrombocytopenic purpura (ITP or AITP).
  • Secondary auto-immune thrombocytopenia.
  • Acute post viral thrombocytopenia.
  • Drug induced thrombocytopenia.
  • Allo-immune:
  • Neonatal purpura.
  • post transfusion purpura.
  • purpura associated with connective tissue diseases or solid tumors or infections (bacterial, viral or parasitic).

Non-immune:

It includes sequestration disorders e.g. DIC, hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura(TTP), giant hemangiomas and splenomegally (hypersplenism).

Abnormal distribution (dilutional)

It is seen after multiple transfusions.

Auto-immune idiopathic thrombocytopenic purpura (AITP,ITP)

It is an acquired disease characterized by thrombocytopenia caused by antibody formation.

Clinical features:

  • It occurs at any age, but most commonly in children and young adults.
  • In children, females : males ratio is 1:1; while in young adults, the incidence in females is more than males.
  • Bleeding is the most important feature which is either spontaneous or follow trauma.
  • Bleeding is either from skin (purpura or ecchymotic spots mostly on legs, forearms, chest or neck), or from mucus membranes (epistaxis, gum bleeding or hematuria), or in the eyes (conjunctival or retinal bleeding).
  • Purpura on skin is called dry purpura, while purpura on mucus membranes (e.g. palate) is called wet purpura.
  • On examination: No splenomegally, no hepatomegally, no lymphadenopathy and no jaundice.
  • Splenomegally is found in only 10% of cases, so presence of splenomegally doesn't exclude ITP.

Clinical courses

  1. Acute (post viral):
  2. It occurs in children aged 2-6 years.
  3. Female : male incidence is equal.
  4. There is usually a history of preceding viral infection few weeks earlier.
  5. Spontaneous recovery is common, usually within days or up to 12 weeks, some cases may have delayed recovery for even 6 months.
  6. Small percentage of patients can progress to chronic form.
  7. Bleeding is acute (sudden onset) and most severe at star then decline as time passes (regress severity).
  8. Chronic:
  • It occurs in young adults and middle age people.
  • Female : male incidence is 3:1.
  • No history of preceding viral infection.
  • It follow a chronic course of on and off bleeding, remissions may occur for months and years followed by relapse.
  • Bleeding is insidious (slowly occurring-not sudden).

3. Secondary auto-immune thrombocytopenic purpura:

  • It is associated with lymphoma, chronic lymphocytic leukemia (CLL), systemic lupus erythematosus (SLE) and bone marrow transplantation.

Lab. diagnosis

  1. Blood film:
  2. Thrombocytopenia (low platelets count).
  3. Platelets morphology is either normal, abnormally large or atypical forms.
  4. Anemia may be seen if long period of bleeding.
  5. Leukocytes count is normal or slightly increased.
  6. Normal ESR.
  7. Bleeding time is prolonged.
  8. Tourniquet test: Check blood pressure then put sphygmomanometer pressure at a level between systolic and diastolic pressures for 5 minutes then remove it and look for prtichae in the forearm. It is positive in thrombocytopenia, impaired platelets function and abnormal vascular integrity.
  9. Bone marrow study: Increased megakaryocytes without morphological abnormalities indicates peripheral destruction; while presence of morphological abnormalities indicates abnormal production e.g. myelodysplastic syndrome.
  10. Tests for immunological nature of disease:
  • Platelets associated IgG antibodies are found in 90% of cases.
  • Anti-platelets antibodies in the serum are found in only 60% of cases as most antibodies are attached to platelets so they aren't found in serum.

Treatment

  • Steroids is the treatment of choice. It is given in a dose of 1-2 mg/kg for 3-4 weeks then gradual tapering to lowest possible dose that keep remission.
  • Cytotoxic drugs may be given with steroids as steroid sparing agent or if relapse occur after steroids tapering.
  • Splenectomy is the last choice if prolonged poor responding ITP.
  • Platelets concentrate is of minimal benefit as it will be destroyed by anti-platelets antibodies; however it may be given in severe thrombocytopenia (platelets count less than 10 ×109/L) as it is a life threatening condition because of the risk of intra-cranial hemorrhage.
  • Intravenous gamma globulin may be given in severe cases to raise platelets count rapidly waiting for steroids to start action.
  • In childhood ITP, spontaneous recovery is usual. Treatment may be avoided in mild cases. While in adulthood type, steroids almost always needed for 3-6 months and then if no response, splenectomy would be the choice.