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The clinical signs and symptoms of immune thrombocytopaenic purpura (ITP) are caused by an increased rate of premature platelet destruction, occurring preferentially in the spleen, liver, bone marrow and lungs. The severity reflects balance between platelet production by megakaryocytes and the accelerated clearance of sensitised platelets. It can be regarded as an inappropriate immune recovery after an infection.
Acute ITP in children tends to occur between two-to-five years of age and affects boys and girls equally. ITP in this group tends to improve spontaneously. Acute ITP in older children and teenagers tends to affect females more than males and is more commonly associated with other autoimmune diseases. Chronic ITP is classified as ITP lasting longer than six months, although it is suggested that this term be reserved for thrombocytopaenia lasting more than one year, due to the fact that spontaneous remission frequently occurs between six-to-12 months. It is suggested that thrombocytopaenia persists for longer than six months in about 25 per cent of children aged under 10 years, whereas in children aged over 10 years the percentage increases to almost 50 per cent.
Early treatment of acute ITP has no effect on those who eventually go on to have chronic ITP. Children with chronic ITP may not require treatment because many children maintain platelets >20×109/l without significant bleeding. Spontaneous recovery has occurred irrespective of the duration of thrombocytopenia.
The presence of generalised bruising and petechiae in the above case report suggest a primary haemostatic defect. Other symptoms of a primary haemostatic defect would be epistaxis, oral bleeding, menorrhagia and other mucosal bleeding.
Table 1: Causes of primary haemostatic defects
The contributors to primary haemostasis are the blood vessel wall, von Willebrand factor and platelets, and abnormalities in these areas will cause similar symptoms (Table 1). It seems unlikely that the child has an inherited disorder of primary haemostasis, such as a collagen vascular disorder, von Willebrand disease or platelet function defect because he has previously been asymptomatic, his physical examination is normal (in particular, no abnormal scarring) and there is no family history of bleeding. An acquired defect seems most likely. There is a preceding history of an upper respiratory infection and this could have produced a vasculitis or thrombocytopaenia, but, as he has a normal exam and is otherwise well, thrombocytopaenia would be the first differential. However, if he does have thrombocytopaenia, all possible causes need to be considered (Table 2).
Table 2: Causes of thrombocytopaenia
The most sensible first step is to check FBC, blood film, coagulation profile (PT, APTT and fibrinogen) and biochemistry (urea and electrolytes, liver function) including LDH and urate. In this case, biochemistry and coagulation were normal. FBC demonstrated an isolated thrombocytopaenia (Hb123g/l, WBC 6.5×109/l with normal differential, platelets 6×109/l) and a blood film that was normal, apart from the lack of platelets. This suggests a diagnosis of viral-induced ITP.
It is important to note, however, that if any abnormalities are found, other than an isolated thrombocytopaenia, other diagnoses are potentially more likely and further investigations, including bone marrow examination, may have to be considered.
Acute ITP in young children is a self-limiting condition, typically resolving in six weeks to six months in more than 80 per cent of children.
Specific treatment is not required in the absence of bleeding. Severe bleeding, eg, protracted epistaxis or gastrointestinal haemorrhage, leading to anaemia requiring transfusion is fortunately rare. Intracranial haemorrhage (ICH) is the most feared complication but has an estimated incidence of only 0.1-0.5 per cent and more than 50 per cent will present with ICH at diagnosis or within one week of diagnosis.
Parents and children should be counselled regarding rough play, contact sport, climbing and trampoline and bouncy castle use. Intramuscular injections should be withheld until the platelet count improves.
Specific medicines that interfere with platelet function, eg, nonsteroidal anti-inflammatories, aspirin, SSRIs and anticonvulsants should be avoided if possible. Platelet counts do not need to be checked more than once every one-to-two weeks and disruption of school or work is not necessary.
If treatment is required, either because of significant bleeding or parental preference, then immunoglobulin (IvIg) is the treatment of choice. It is thought to function by saturating the Fc receptors on the reticuloendothelial cells in the liver and spleen, decreasing the clearance of opsonised platelets.
The dose given is 0.8-1g/kg for one-to-three days. A rise is seen within 24-to-72 hours, peaking at nine days and lasting two-to-four weeks. More than 80 per cent of children will respond.
Unfortunately, IvIg is not without side-effects. Generally, these symptoms are mild, eg, nausea, light-headedness and headache but occasionally a severe headache may ensue, necessitating a CT scan. Rarely anaphylaxis, aseptic meningitis and pulmonary and renal failure have been reported.
Tranexamic acid has been utilised for those with prolonged thrombocytopaenia and persistent mucosal bleeding without anaemia (mild bleeding) with reported efficacy and minimal side-effects.
Other therapies which can be used include Anti-D, which has been used in patients who are rhesus positive, non-splenectomised and not anaemic, and corticosteroids.
Anti-D has been associated with a rare but potentially fatal haemolysis or disseminated intravascular coagulopathy and so is generally not favoured. The dose and type of corticosteroid given is usually 2-4mg/kg of prednisolone, administered daily for two-to-four weeks and then tapered slowly. The response usually takes three-to-four days, but the initial response rate is 70-90 per cent.
Patients with a life-threatening bleed and platelets <10×109/l should be treated aggressively and urgently. Immunoglobulin 1g/kg/day for two-to-three days with concomitant high-dose steroid (methylprednisolone 30mg/kg/day to a maximum of 1g/day) and random donor platelets should be administered.
Off-label use of recombinant factor VIIa may be considered, as may emergency splenectomy.
References on request
A three-year-old boy presented to the emergency department with a reported two-day history of a rash and easy bruising. He denied any other bleeding, including epistaxis, oral bleeding, haematuria or bleeding per rectum. He had been very well except for an upper respiratory tract infection two weeks ago. He had no other past history of note and, in particular, there had been no bleeding with intramuscular vaccines and no history of past surgery. There was no family history of bleeding disorders and when questioned specifically, there was no family history of epistaxis, menorrhagia, oral mucosal bleeding or excessive bleeding with trauma or surgery. Similarly, there was no history of autoimmune disorders. The child had not been taking any medications recently.
His vital signs were normal and he was on the 50th percentile for height and weight. He appeared well but had bruising and petechiae all over his body. There was no overt bleeding and no hepatosplenomegaly, but he did have shotty cervical adenopathy.