A case of severe neonatal thrombocytopenia with schizencephaly associated with anti-HPA-1b and anti-HPA-2a

Severe intracranial haemorrhage in neonatal alloimmune thrombocytopenia due to antibodies against human platelet antigen 1b: Case report and literature review

Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a rare life-threatening disorder, leading to severe thrombocytopenia and potentially bleeding, with intracranial haemorrhage (ICH) being the most serious complication. We report on a FNAIT case with fourth-degree ICH that arose due to antibodies against human platelet antigen (HPA)-1b. The male infant, born to an otherwise healthy mother, presented with severe signs of ICH soon after delivery. Since only moderate thrombocytopenia was noted and there were no active signs of bleeding, the infant did not receive intravenous immunoglobulins (IVIg) or platelet transfusion. Spontaneous recovery of platelets was noted on the eighth day of life, but permanent neurological impairment remained as a consequence of ICH. We report the results of HPA and human leukocyte antigen (HLA) antibodies in the mother's and the infant's sera, the family's HPA genotype and the mother's HLA genotype, and summarise previously described cases of FNAIT due to anti-HPA-1b antibodies in the literature. FNAIT with severe ICH due to anti-HPA-1b antibodies is rarely diagnosed. An association between HLA genes and sensitization to HPA-1b antibodies was not demonstrated. The severity of FNAIT and the occurrence of ICH is often difficult to predict. In this case, the infant presented with moderate thrombocytopenia and ICH, with subsequent permanent consequences.

The spectrum of brain malformations and disruptions in twins

Twins have an increased risk for congenital malformations and disruptions, including defects in brain morphogenesis. We analyzed data on brain imaging, zygosity, sex, and fetal demise in 56 proband twins and 7 less affected co-twins with abnormal brain imaging and compared them to population-based data and to a literature series. We separated our series into malformations of cortical development (MCD, N = 39), cerebellar malformations without MCD (N = 13), and brain disruptions (N = 11). The MCD group included 37/39 (95%) with polymicrogyria (PMG), 8/39 (21%) with pia-ependymal clefts (schizencephaly), and 15/39 (38%) with periventricular nodular heterotopia (PNH) including 2 with PNH but not PMG. Cerebellar malformations were found in 19 individuals including 13 with a cerebellar malformation only and another 6 with cerebellar malformation and MCD. The pattern varied from diffuse cerebellar hypoplasia to classic Dandy-Walker malformation. Brain disruptions were seen in 11 individuals with hydranencephaly, porencephaly, or white matter loss without cysts. Our series included an expected statistically significant excess of monozygotic (MZ) twin pairs (22/41 MZ, 54%) compared to population data (482/1448 MZ, 33.3%; p = .0110), and an unexpected statistically significant excess of dizygotic (DZ) twins (19/41, 46%) compared to the literature cohort (1/46 DZ, 2%; p < .0001. Recurrent association with twin-twin transfusion syndrome, intrauterine growth retardation, and other prenatal factors support disruption of vascular perfusion as the most likely unifying cause.

Advances in alloimmune thrombocytopenia: perspectives on current concepts of human platelet antigens, antibody detection strategies, and genotyping

Alloimmunisation to platelets leads to the production of antibodies against platelet antigens and consequently to thrombocytopenia. Numerous molecules located on the platelet surface are antigenic and induce immune-mediated platelet destruction with symptoms that can be serious. Human platelet antigens (HPA) cause thrombocytopenias, such as neonatal alloimmune thrombocytopenia, post-transfusion purpura, and platelet transfusion refractoriness. Thirty-four HPA are classified into 28 systems. Assays to identify HPA and anti-HPA antibodies are critically important for preventing and treating thrombocytopenia caused by anti-HPA antibodies. Significant progress in furthering our understanding of HPA has been made in the last decade: new HPA have been discovered, antibody-detection methods have improved, and new genotyping methods have been developed. We review these advances and discuss issues that remain to be resolved as well as future prospects for preventing and treating immune thrombocytopenia.

Schizencephaly prevalence, prenatal diagnosis and clues to etiology: a register-based study

OBJECTIVES

To establish the prevalence and antenatal diagnosis of schizencephaly in the UK.

METHODS

Data on schizencephaly were extracted from six regional congenital anomaly registers.

RESULTS

Thirty-eight cases of schizencephaly were identified in 2 567 165 livebirths and stillbirths, giving a total prevalence of 1.48/100 000 births (95% CI, 1.01-1.95). Eighteen (47% (95% CI, 31-63%)) of the 38 cases were identified antenatally. No affected fetus had an abnormal karyotype identified. A high proportion of cases of schizencephaly occurred in younger mothers: 63% were aged 24 years or less, significantly higher (P < 0.0001) than the corresponding proportion (26%) of mothers in England and Wales. The majority of cases were not identified until after 22 weeks of pregnancy. Additional anomalies associated with vascular disruption sequences were found in eight cases which had septo-optic dysplasia or absent septum pellucidum, one of which also had gastroschisis.

CONCLUSIONS

Schizencephaly occurs more frequently in the fetuses of younger mothers. It is often associated with septo-optic dysplasia, suggesting that the two conditions may share a common origin, arising as a result of destructive processes that cause changes in the brain which only become apparent on ultrasound in the second half of pregnancy.

Prenatal stroke

The main focus of this chapter is the comprehensive description of the neuropathology, the imaging correlates and underlying mechanisms of prenatal stroke. We describe established prenatal stroke in subgroups similar to postnatal stroke: arterial (forebrain or hindbrain) infarction, venous thrombosis, primary lobar haemorrhage. This longitudinal classification should facilitate the study of risk factors and mechanisms. Forebrain lesions of arterial type present as porencephaly, (hemi)hydranencephaly, multicystic encephalopathy or schizencephaly. Venous prenatal forebrain stroke presents as simple porencephaly (in some of genetic nature) and sinus thrombosis. A list of rare porencephaly-like conditions is added for differentiation from arterial and venous porencephaly. Hindbrain infarctions (so far the only reported variants seem to be of arterial nature) present as brainstem disconnection, focal brainstem destruction, uni- or bilateral cerebellar destruction and focal spinal cord ischaemia. Prenatal intracranial haemorrhage and congenital brain infection should be considered in the differential diagnosis of prenatal stroke.

Fetal and neonatal alloimmune thrombocytopenia: progress and ongoing debates

Fetal and neonatal alloimmune thrombocytopenia (AIT) is a result of a parental incompatibility of platelet-specific antigens and the transplacental passage of maternal alloantibodies against the platelet antigen shared by the father and the fetus. It occurs in approximately 1 in 1000 live births and is the most common cause of severe thrombocytopenia in fetuses and term neonates. As screening programs are not routinely performed, most affected fetuses are identified after birth when neonatal thrombocytopenia is recognized. In severe cases, the affected fetus is identified as a result of suffering from an in utero intracranial hemorrhage. Once diagnosed, AIT must be treated antenatally as the disease can be more severe in subsequent pregnancies. While there have been many advances regarding the diagnosis and treatment of AIT, it is still difficult to predict the severity of disease and which therapy will be effective.

Schizencephaly: heterogeneous etiologies in a population of 4 million California births

Schizencephaly is a rare congenital brain defect characterized by gray matter lined clefts of the cerebral mantle, frequently accompanied by other defects of the CNS such as absence of the corpus callosum. This study in a California population of >4 million births from 1985-2001 found a population prevalence of 1.54/100,000. Among 63 cases, there was an association with young parental age in isolated schizencephaly (RR 3.9 mothers; 5.8 fathers), which was also seen in mothers but not fathers of non-isolated cases (RR 3.2). Monozygotic twins may also be at increased risk for schizencephaly (RR 2.1). One third of cases had a non-CNS abnormality, over half of which could be classified as secondary to vascular disruption, including gastroschisis, bowel atresias, and amniotic band disruption sequence. Other apparent rare causes included chromosomal aneuploidy, non-random associations, and unusual syndromes. Our observations suggest that schizencephaly has heterogeneous etiologies many of which are vascular disruptive in origin.

EMX2-independent familial schizencephaly: Clinical and genetic analyses

Schizencephaly is a human brain malformation distinguished by full-thickness unilateral or bilateral clefts through the neocortex. Heterozygous mutations in the EMX2 locus are reported to give rise to schizencephaly. However, the comprehensive identification of causative genetic loci is precluded by a lack of large pedigrees and genome-wide linkage analyses. We present here a large Turkish pedigree with three individuals with schizencephaly. The similarity of clinical signs in affected individuals strongly suggests an underlying genetic cause; however, genome-wide linkage analysis rules out EMX2 linkage and instead suggests additional candidate loci. These results indicate that genetic forms of schizencephaly are likely to be heterogeneous.

Will it ever be possible to balance the risk of intracranial haemorrhage in fetal or neonatal alloimmune thrombocytopenia against the risk of treatment strategies to prevent it?

BACKGROUND AND OBJECTIVES

Intracranial haemorrhage (ICH) of the fetus or newborn is a severe complication of fetal or neonatal alloimmune thrombocytopenia (FNAIT). In order to attain management decisions to prevent ICH, the risk of ICH in successive pregnancies with thrombocytopenia, with or without a history of ICH, must be established.

MATERIALS AND METHODS

We performed a search of medline for ICH cases in untreated FNAIT pregnancies. After exclusion of cases with confounding factors, 24 reports, describing 62 pregnancies of 27 mothers, were eligible. In addition, two mothers with five pregnancies were included from our own case records. Observational studies were examined to estimate the risk of ICH in subsequent FNAIT pregnancies without a history of ICH. Finally, medline was searched for complication rates in the treatment of FNAIT pregnancies.

RESULTS

In 52% of the ICH cases, a previous sibling suffered from ICH. The recurrence rate of ICH in the subsequent offspring of women with a history of FNAIT with ICH was 72%[confidence interval (CI): 46-98%] without inclusion of fetal deaths and 79% (CI: 61-97%) with inclusion of fetal deaths. In 48% of the ICH cases, the previous sibling had thrombocytopenia but not ICH. Population studies revealed an overall ICH risk in thrombocytopenic infants of 11% (CI: 0.8-23%) without inclusion of fetal deaths and 15% (CI: 1.5-19%) with inclusion of fetal deaths. Assuming occurrence in 48%, the risk of ICH in a subsequent pregnancy following a history of FNAIT without ICH, was estimated to be 7% (CI: 0.5-13%). Invasive treatment strategies carry a risk of 2.8% (CI: 1.2-4.4%) on complications.

CONCLUSIONS

The number of eligible publications on ICH in untreated FNAIT pregnancies is strikingly limited. The recurrence rate is high. As sufficient data on successive FNAIT cases without ICH are lacking, the occurrence of ICH in pregnancies with thrombocytopenia, but without ICH in a previous sibling, cannot be predicted. We estimate this risk to be 7%. This risk must be balanced against the risk of interventions in treatment strategies.

Feto-maternal alloimmune thrombocytopenia: a literature review and statistical analysis

Exploring prognostic factors that determine outcomes in fetomaternal alloimmune thrombocytopenia (FMAIT), a search of Medline was performed covering the years 1966 to April 1998. 376 articles were collected and reviewed; 140 articles contained the case histories of 297 mothers and 433 pregnancies that fulfilled entry criteria. More than 30 data variables were sought from these cases. The data were analysed using SPSS and Arcus Quickstat Biomedical. Nineteen different antigen incompatibilities were documented, the majority being human platelet antigen (HPA)-1a (77.3%), HPA-3a (3.5%) and HPA-5b (3.5%). The relative risk reduction (RRR) in mortality with any intervention was 57% (0.19-0.77) p = 0.009. Treatment of HPA-1a (PlA1) pregnancies with intravenous immunoglobulin (IVIG) increased the likelihood of a neurologically normal outcome, relative risk (RR) 1.68, confidence interval (1.3-2.2) p = 0.0003. Treatment of HPA-1a (PlA1) pregnancies with only antenatal complementary platelet transfusions increased the likelihood of a neurologically normal outcome, RR 1.63 (1.1-2.1) p = 0.01. Despite reviews of more than 400 cases of FMAIT, few prognostic variables are identifiable. Although IVIG appears to reduce the risk of intracranial haemorrhage (ICH), the dosage and timing of IVIG treatment was varied. This study highlights the need for standardised and directed research.

Schizencephaly: clinical and imaging features in 30 infantile cases

Schizencephaly is an uncommon structural disorder of cerebral cortical development, characterized by congenital clefts spanning the cerebral hemispheres from the pial surface to the lateral ventricles and lined by cortical gray matter. Either an antenatal environmental incident or a genetic origin could be responsible for this lesion which occurs between the third and fourth month of gestation. We report the clinical and cranial imaging features of 30 children, of whom 15 had unilateral and 15 had bilateral lesions. Their ages at the time of the first presentation ranged from 1 month to 10 years. They were thoroughly studied from clinical, epileptical, imaging and electroencephalographic (EEG) viewpoints. Five patients were investigated by cranial computed tomography (CT), eight by cranial magnetic resonance (MR) imaging, and 17 by both methods. The clinical features consisted of mild hemiparesis in 17 cases (57%), 12/17 were related to a unilateral phenotype (80% of all unilateral forms) and 5/17 to a bilateral phenotype. A tetraparesis was present in nine cases, all of which were due to a bilateral cleft. Bilateral forms were significantly associated with tetraparesis, whereas unilateral forms were associated with hemiparesis. Mental retardation was observed in 17 cases (57%), and was observed significantly more often in bilateral clefts (80%). When both hemispheres are involved, an absence of reorganization of the brain function between the two hemispheres leads to severe mental deficits, in addition to the cerebral anomaly itself. Eleven patients had seizures (seven from unilateral and three from bilateral forms). The degree of malformation was not related to the severity of epilepsy. Migration disorders, such as dysplasia or heterotopia, were observed in 30% of cases and are also important etiopathogenetic factors. The septum pellucidum was absent in 13 cases (43%), with septo-optical dysplasia in two cases. Corpus callosum dysgenesis was noted in 30% of cases. Four cases of mega cisterna magna were noted. Although familial cases and environmental factors have been previously reported, schizencephaly appears to be, in the majority of cases, sporadic.

The management of alloimmune neonatal thrombocytopenia

Neonatal alloimmune thrombocytopenia (NAITP), defined as thrombocytopenia (platelet count < 150 x 10(9)/l) due to transplacentally acquired maternal platelet alloantibodies, occurs in approximately 1 per 1200 live births in a Caucasian population. In such a population, the majority (> 75 percent) of cases are due to fetomaternal incompatibility for the platelet specific alloantigen, HPA-1a (P1A1, Zwa). Incompatibility for the HPA-5b (Bra) alloantigen is the next most frequent cause of NAITP in Caucasians; much less common is NAITP due to incompatibility for HLA, blood group ABO or other platelet-specific antigens. In non-Caucasian populations (e.g. Orientals) HPA-1a incompatibility is a rare cause of NAITP and other alloantigens e.g. HPA-4b (Penb, Yuka) are implicated. The greatest clinical challenge relates to the antenatal management of pregnant women alloimmunized to the HPA-1a (P1A1, Zwa) antigen, and particularly the subset of such women who have a history of a previously affected infant with severe thrombocytopenia and/or intracranial hemorrhage (ICH). The risk of antenatal ICH in the fetus of such women is high enough to merit intervention, either weekly infusion of high-dose intravenous immunoglobulin G (IVIG) with or without corticosteroids given to the mother (the preferred approach in North American centres), or repeated in-utero fetal platelet transfusions (the preferred treatment approach in some European centres). Post-natal management of severely affected infants centres on the rapid provision of compatible antigen-negative platelets harvested from the mother or a phenotyped donor. The value of antenatal screening programs to detect 'at risk' alloimmunized women during pregnancy continues to be debated.