A case of thrombotic thrombocytopenic purpura and neonatal alloimmune thrombocytopenia in the same pregnancy

Abstract

Case reportA 26 year old primigravida with a past history of Hashimoto's thyroiditis required urgent admission at 21 weeks of gestation due to decreased level of consciousness, paraesthesiae of the right hand, slurred speech and difficulty in swallowing. The woman was disorientated and mildly febrile. There was no evidence of hypertension, bleeding or purpuric lesions. An automated blood count revealed normocytic anaemia (haemoglobin 48 g/L, MCV 97.8 fl), a haematocrit of 0.141 and thrombocytopenia (platelet count 14 Â 10 9 /L). Many schistocytes and nucleated red blood cells were present on the blood smear. Lactate dehydrogenase was elevated (1224 iu/L). Her clotting screen, liver and renal function tests were normal. Stool cultures were negative for E. coli 0157.Her clinical features were compatible with microangiopathy due to thrombotic thrombocytopenic purpura. She was treated with daily plasma exchange using cryo-poor plasma as a replacement fluid. A transfusion of red cell concentrate was also given, and calcium and folate supplements were prescribed.The woman responded well to plasma exchange, and her focal neurological signs resolved within three days. Ultrasonography revealed normal fetal anatomy and growth. Aspirin (81 mg daily) was begun when the platelet count rose above 50 Â 10 9 /L. Corticosteroids were administered a week after admission, while the diagnosis of autoimmune thrombocytopenia was still being entertained, and a betablocker was prescribed to control her borderline hypertension. Intramuscular betamethasone was given at 24 weeks of gestation to promote the production of surfactant in the infant's lungs. Blood counts stabilised with haemoglobin 80 -95 g/L, platelet count 230 Â 10 9 /L and lactate dehydrogenase 140-170 iu/L. Further laboratory analysis revealed no evidence of lupus anticoagulant, anticardiolipin antibodies, anti-nuclear antibodies or rheumatoid factor.She went home at 26 weeks of gestation, but continued with plasma exchange three times weekly and frequent ultrasonography. At 29 weeks of gestation, an ultrasound scan showed bilateral fetal intracerebral haemorrhages, and the woman was readmitted. Her platelet count, haemoglobin and lactate dehydrogenase levels were unchanged from her previous admission, suggesting no deterioration of her thrombotic thrombocytopenic purpura. In view of the haemorrhagic features in the fetus, a diagnosis of neonatal alloimmune thrombocytopenia was considered. Solvent detergent-treated intravenous immunoglobulin 1 g/kg was administered. The woman's genotype for platelet-specific antigens (HPA) was HPA-1b (PL A2/A2 ); her partner's genotype was HPA-1a (PL A1/A1 ). An anti-HPA-1a (anti-PL A1 ) antibody was identified in the mother's serum, confirming the diagnosis of neonatal alloimmune thrombocytopenia.Plasma exchanges were continued three times weekly, alternating with twice weekly infusions of immunoglobulin. Ultrasound scans of the fetal head were performed weekly. By 32 weeks of gestation, a porencephalic cyst measuring 29 Â 37 Â 26 mm was ...