Platelet abnormalities in the neonate and childhood

C7. Platelet abnormalities in the neonate and childhood

Thrombocytopenia

Thrombocytopenia is a frequent occurrence amongst ill newborns, being found in 20–30% of all admissions to a neonatal intensive care ward. It is more common among infants with neonatal asphyxia, respiratory distress syndrome, pulmonary hypertension and meconium aspiration. The aetiology of the thrombocytopenia is not understood. The platelet life span is decreased while the megakaryocyte numbers are normal or increased. These features are also seen in infection, disseminated intravascular coagulation and immune/mechanical destruction.

Most infants with thrombocytopenia come to the attention of the neonatologist because of haemorrhagic symptoms: petechiae, purpura, epistaxis or mucous membrane bleeding.

Mechanisms of thrombocytopenia in neonates and children fall into two basic categories:

• Increased destruction

• Impaired or ineffective thrombopoiesis.

Thrombocytopenia due to increased destruction

Idiopathic thrombocytopenic purpura (ITP)

ITP is one of the most frequently seen examples of increased platelet destruction. A typical history is bruising and petechiae appearing suddenly in a child who is otherwise in excellent health. The peak age for the diagnosis of ITP is 2 to 4 years. In childhood ITP, males and females are affected with equal frequency—in contrast to adult ITP, in which females dominate by a 3:1 ratio. Often there is a history of a viral illness or vaccination 1 to 3 weeks prior to presentation. The platelet count in these children is commonly <10 × 10⁹/L. The blood film should be carefully scanned for the presence of reactive lymphocytes as well as large platelets when a case of ITP is suspected.

In the majority of cases, ITP in children is an acute self-limiting disease resolving within 6 months whether or not therapy is given. Refer to Fig C7-1.

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Figure C7-1

Idiopathic thrombocytopenic purpura (ITP): peripheral blood film showing a reactive T lymphocyte in a 3-year-old child with post viral ITP. The platelet count is less than 1 x 10⁹/L. (x 1000)

Thrombocytopenia due to impaired or ineffective thrombopoiesis

Amegakaryocytic thrombocytopenia (AMEGA)

AMEGA occurs in infancy and early childhood. The mode of inheritance is either X-linked or autosomal-recessive. AMEGA is a very rare disorder in which patients present with a petechial rash, bruising or bleeding in the first year of life. Mild to moderate anaemia and leucopenia may be present. Megakaryocytes in the bone marrow are either reduced in number or absent. Granulopoiesis and erythropoiesis are normal. The red cells may be macrocytic and the HbF increased.

Between 20% and 40% of cases may develop aplastic anaemia in the first few years of life.

Patients with AMEGA have a predisposition to develop acute leukaemia. Refer to Figure C7-2 and Figure C7-3.

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Tags: Microscopic Haematology

Jun 12, 2016 | Posted by admin in HEMATOLOGY | Comments Off

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