Casanova and colleagues discuss the importance of single-patient genetic studies in the discovery of novel primary immunodeficiencies and offer insight into the standards and criteria that should accompany these studies.
Can genetic and clinical findings made in a single patient be considered sufficient to establish a causal relationship between genotype and phenotype? We report that up to 49 of the 232 monogenic etiologies (21%) of human primary immunodeficiencies (PIDs) were initially reported in single patients. The ability to incriminate single-gene inborn errors in immunodeficient patients results from the relative ease in validating the disease-causing role of the genotype by in-depth mechanistic studies demonstrating the structural and functional consequences of the mutations using blood samples. The candidate genotype can be causally connected to a clinical phenotype using cellular (leukocytes) or molecular (plasma) substrates. The recent advent of next generation sequencing (NGS), with whole exome and whole genome sequencing, induced pluripotent stem cell (iPSC) technology, and gene editing technologies—including in particular the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology—offer new and exciting possibilities for the genetic exploration of single patients not only in hematology and immunology but also in other fields. We propose three criteria for deciding if the clinical and experimental data suffice to establish a causal relationship based on only one case. The patient’s candidate genotype must not occur in individuals without the clinical phenotype. Experimental studies must indicate that the genetic variant impairs, destroys, or alters the expression or function of the gene product (or two genetic variants for compound heterozygosity). The causal relationship between the candidate genotype and the clinical phenotype must be confirmed via a relevant cellular phenotype, or by default via a relevant animal phenotype. When supported by satisfaction of rigorous criteria, the report of single patient–based discovery of Mendelian disorders should be encouraged, as it can provide the first step in the understanding of a group of human diseases, thereby revealing crucial pathways underlying physiological and pathological processes.
The present uncertainty of which live viral or bacterial vaccines may be given to immune deficient patients and the growing neglect of societal adherence to routine immunizations has prompted the Medical Advisory Committee of the Immune Deficiency Foundation to issue recommendations based upon published literature and the collective experience of the committee members. These recommendations address the concern for immunodeficient patients acquiring infections from healthy individuals who have not been immunized or who are shedding live vaccine-derived viral or bacterial organisms. Such transmission of infectious agents may occur within the hospital, clinic, home, or at any public gathering. Collectively, we define this type transmission as close-contact spread of infectious disease that is particularly relevant in patients with impaired immunity who may develop infection when exposed to individuals carrying vaccine-preventable infectious diseases or who have recently received a live vaccine. Immunodeficient patients who have received therapeutic hematopoietic stem transplantation are also at risk during the time when immune reconstitution is incomplete or while they are on immunosuppressive agents to prevent or treat graft-versus-host disease.
This review recommends the general education of what is known about vaccine-preventable or vaccine-derived diseases being spread to immunodeficient patients at risk for close-contact spread of infection, and describes the relative risks for a child with severe immunodeficiency. The review also recommends a balance between the need to protect vulnerable individuals with their social needs to integrate into society, attend school, and benefit from peer education.
Live Viral and Bacterial Vaccines; Primary Immunodeficiency Disease; Severe Combined Immunodeficiency Disease; Cellular Immune reconstitution
Most children who are exposed to large quantities of alcohol in utero do not develop fetal alcohol syndrome (FAS). Population-based prospective data on the risk of developing components of fetal alcohol spectrum disorders (FASD), however, are limited.
This was a prospective cohort study of 9,628 women screened during their first prenatal appointment in Chile, which identified 101 who consumed at least 4 drinks/d (exposed) matched with 101 women with no reported alcohol consumption during pregnancy (unexposed). Detailed alcohol consumption data were collected during the pregnancy. Children were evaluated up to 8.5 years of age by clinicians masked to exposure status.
One or more functional central nervous system abnormalities were present in 44.0% (22/50) of the exposed children compared to 13.6% (6/44) of the unexposed (p = 0.002). Growth restriction was present in 27.2% (25/92) of the exposed and 12.5% (12/96) of the unexposed (p = 0.02). Abnormal facial features were present in 17.3% (14/81) of the exposed children compared to 1.1% (1/89) of the unexposed children (p = 0.0002) by direct examination. Of the 59 exposed children with data available to detect at least 1 abnormality, 12 (20.3%) had no abnormalities. Binge drinking from conception to recognition of pregnancy (OR = 1.48 per day, 95% CI: 1.15 to 1.91, p = 0.002) and after recognition of pregnancy (OR= 1.41 per day, 95% CI: 1.01 to 1.95, p = 0.04) and total number of drinks consumed per week from conception to recognition of pregnancy (OR = 1.02 per drink, 95% CI: 1.01 to 1.04, p = 0.0009) were significantly associated with abnormal child outcome.
After exposure to heavy alcohol consumption during pregnancy, 80% of children had 1 or more abnormalities associated with alcohol exposure. Patterns of alcohol use that posed the greatest risk of adverse outcomes were binge drinking and high total weekly intake. Functional neurologic impairment occurred most frequently and may be the only sign to alert physicians to prenatal alcohol exposure.
Alcohol; Pregnancy; Fetal Alcohol Spectrum Disorders; Growth Restriction; Neurodevelopment
We prospectively identified 96 women consuming at least 4 drinks/day during pregnancy by screening 9628 pregnant women. In these women with heavy prenatal alcohol use, there were three stillbirths and one preterm delivery; 98 matched nondrinking women had no stillbirths and two preterm births. Preterm rates did not differ significantly. The stillbirth rate was higher in the exposed group (p = 0.06). Additional investigation showed the stillbirth rate in the exposed population (3.1%) was significantly higher (p = 0.019) than the reported Chilean population rate (0.45%). Our data suggest that heavy alcohol consumption may increase the risk for stillbirth but not preterm delivery.
alcohol; pregnancy; stillbirth; preterm delivery; binge drinking
Women who have low cobalamin (vitamin B12) levels are at increased risk for having children with neural tube defects (NTDs). The transcobalamin II receptor (TCblR) mediates uptake of cobalamin into cells. We evaluated inherited variants in the TCblR gene as NTD risk factors.
Case-control and family-based tests of association were used to screen common variation in TCblR as genetic risk factors for NTDs in a large Irish group. A confirmatory group of NTD triads was used to test positive findings.
We found two tightly linked variants associated with NTDs in a recessive model: TCblR rs2336573 (G220R) (pcorr=0.0080, corrected for multiple hypothesis testing) and TCblR rs9426 (pcorr =0. 0279). These variants were also associated with NTDs in a family-based test prior to multiple test correction (log-linear analysis of a recessive model: rs2336573 (G220R) (RR=6.59, p=0.0037) and rs9426 (RR=6.71, p=0.0035)). We describe a copy number variant (CNV) distal to TCblR and two previously unreported exonic insertion-deletion polymorphisms.
TCblR rs2336573 (G220R) and TCblR rs9426 represent a significant risk factor in NTD cases in the Irish population. The homozygous risk genotype was not detected in nearly one thousand controls, indicating this NTD risk factor may be of low frequency and high penetrance. Nine other variants are in perfect LD with the associated SNPs. Additional work is required to identify the disease-causing variant. Our data suggest that variation in TCblR plays a role in NTD risk and that these variants may modulate cobalamin metabolism.
neural tube defects; spina bifida; transcobalamin II receptor (TCblR); cobalamin; vitamin B12; copy number variant (CNV)
The number of genetically defined Primary Immunodeficiency Diseases (PID) has increased exponentially, especially in the past decade. The biennial classification published by the IUIS PID expert committee is therefore quickly expanding, providing valuable information regarding the disease-causing genotypes, the immunological anomalies, and the associated clinical features of PIDs. These are grouped in eight, somewhat overlapping, categories of immune dysfunction. However, based on this immunological classification, the diagnosis of a specific PID from the clinician’s observation of an individual clinical and/or immunological phenotype remains difficult, especially for non-PID specialists. The purpose of this work is to suggest a phenotypic classification that forms the basis for diagnostic trees, leading the physician to particular groups of PIDs, starting from clinical features and combining routine immunological investigations along the way.We present 8 colored diagnostic figures that correspond to the 8 PID groups in the IUIS Classification, including all the PIDs cited in the 2011 update of the IUIS classification and most of those reported since.
Primary immunodeficiency; classification; IUIS; diagnosis tool
Anorectal atresia is a serious birth defect of largely unknown etiology but candidate genes have been identified in animal studies and human syndromes. Because alterations in the activity of these genes might lead to anorectal atresia, we selected 71 common variants predicted to be in transcription factor binding sites, CpG windows, splice sites, and miRNA target sites of 25 candidate genes, and tested for their association with anorectal atresia. The study population comprised 150 anorectal atresia cases and 623 control infants without major malformations. Variants predicted to affect transcription factor binding, splicing, and DNA methylation in WNT3A, PCSK5, TCF4, MKKS, GLI2, HOXD12, and BMP4 were associated with anorectal atresia based on a nominal P value <0.05. The GLI2 and BMP4 variants are reported to be moderately associated with gene expression changes (Spearman’s rank correlation coefficients between −0.260 and 0.226). We did not find evidence for interaction between maternal pre-pregnancy obesity and variants in MKKS, a gene previously associated with obesity, on the risk of anorectal atresia. Our results for MKKS support previously suggested associations with anorectal malformations. Our findings suggest that more research is needed to determine whether altered GLI2 and BMP4 expression is important in anorectal atresia in humans.
anorectal malformations; imperforate anus; hindgut; congenital abnormalities
We report the updated classification of primary immunodeficiencies (PIDs) compiled by the Expert Committee of the International Union of Immunological Societies. In comparison to the previous version, more than 30 new gene defects are reported in this updated version. In addition, we have added a table of acquired defects that are phenocopies of PIDs. For each disorder, the key clinical and laboratory features are provided. This classification is the most up-to-date catalog of all known PIDs and acts as a current reference of the knowledge of these conditions and is an important aid for the molecular diagnosis of patients with these rare diseases.
primary immunodeficiencies; IUIS; classification; genetic defects; genotype
immunodeficiency; classification; gene defects; genotype; IUIS
Approximately 90% of patients with isolated agammaglobulinemia and failure of B cell development have mutations in genes required for signaling through the pre–B cell and B cell receptors. The nature of the gene defect in the majority of remaining patients is unknown. We recently identified 4 patients with agammaglobulinemia and markedly decreased numbers of peripheral B cells. The B cells that could be detected had an unusual phenotype characterized by the increased expression of CD19 but the absence of a B cell receptor. Genetic studies demonstrated that all 4 patients had the exact same de novo mutation in the broadly expressed transcription factor E47. The mutant protein (E555K) was stable in patient-derived EBV-transformed cell lines and cell lines transfected with expression vectors. E555K in the transfected cells localized normally to the nucleus and resulted in a dominant negative effect when bound to DNA as a homodimer with wild-type E47. Mutant E47 did permit DNA binding by a tissue-specific heterodimeric DNA-binding partner, myogenic differentiation 1 (MYOD). These findings document a mutational hot-spot in E47 and represent an autosomal dominant form of agammaglobulinemia. Further, they indicate that E47 plays a critical role in enforcing the block in development of B cell precursors that lack functional antigen receptors.
Hirschsprung’s disease (HSCR) results from failed colonization of the embryonic gut by enteric neural crest cells (ENCCs); colonization requires RET proto-oncogene (RET) signaling. We sequenced RET to identify coding and splice-site variants in a population-based case group and we tested for associations between HSCR and common variants in RET and candidate genes (ASCL1, HOXB5, L1CAM, PHOX2B, PROK1, PROKR1) chosen because they are involved in ENCC proliferation, migration, and differentiation in animal models. We conducted a nested case-control study of 304 HSCR cases and 1 215 controls. Among 38 (12.5%) cases with 34 RET coding and splice-site variants, 18 variants were previously unreported. We confirmed associations with common variants in HOXB5 and PHOX2B but the associations with variants in ASCL1, L1CAM, and PROK1 were not significant after multiple comparisons adjustment. RET variants were strongly associated with HSCR (P values between 10−3 and 10−31) but this differed by race/ethnicity: associations were absent in African-Americans. Our population-based study not only identified novel RET variants in HSCR cases, it showed that common RET variants may not contribute to HSCR in all race/ethnic groups. The findings for HOXB5 and PHOX2B provide supportive evidence that genes regulating ENCC proliferation, migration, and differentiation could be risk factors for HSCR.
congenital abnormalities; enteric nervous system; Hirschsprung disease; RET
Isolated congenital asplenia (ICA) is characterized by the absence of a spleen at birth in individuals with no other developmental defects. The patients are prone to life-threatening bacterial infections. The unbiased analysis of exomes revealed heterozygous mutations in RPSA in 18 patients from eight kindreds, corresponding to more than half the patients and over one third of the kindreds studied. The clinical penetrance in these kindreds is complete. Expression studies indicated that the mutations carried by the patients - a nonsense, a frameshift duplication and five different missense - cause autosomal dominant ICA by haploinsufficiency. Population genetic studies showed that RPSA was subject to purifying selection. RPSA encodes ribosomal protein SA, a component of the small subunit of the ribosome. This discovery establishes an essential role for RPSA in human spleen development.
Individual studies of the genetics of neural tube defects (NTDs) contain results on a small number of genes in each report. To identify genetic risk factors for NTDs, we evaluated potentially functional single nucleotide polymorphisms (SNPs) that are biologically plausible risk factors for NTDs but that have never been investigated for an association with NTDs, examined SNPs that previously showed no association with NTDs in published studies, and tried to confirm previously reported associations in folate-related and non-folate-related genes. We investigated 64 SNPs in 34 genes for association with spina bifida in up to 558 case-families (520 cases, 507 mothers, 457 fathers) and 994 controls in Ireland. Case-control and mother-control comparisons of genotype frequencies, tests of transmission disequilibrium, and log-linear regression models were used to calculate effect estimates. Spina bifida was associated with over-transmission of the LEPR (leptin receptor) rs1805134 minor C allele (genotype relative risk (GRR): 1.5; 95% confidence interval (CI): 1.0, 2.1; P = 0.0264) and the COMT (catechol-O-methyltransferase) rs737865 major T allele (GRR: 1.4; 95% CI: 1.1, 2.0; P = 0.0206). After correcting for multiple comparisons, these individual test P-values exceeded 0.05. Consistent with previous reports, spina bifida was associated with MTHFR 677C>T, T (Brachyury) rs3127334, LEPR K109R, and PDGFRA promoter haplotype combinations. The associations between LEPR SNPs and spina bifida suggest a possible mechanism for the finding that obesity is a NTD risk factor. The association between a variant in COMT and spina bifida implicates methylation and epigenetics in NTDs.
congenital abnormalities; folic acid; neural tube defects; single nucleotide polymorphism; spina bifida
Suggestive, but not conclusive, studies implicate many genetic variants in oral cleft etiology. We used a large, ethnically homogenous study population to test whether reported associations between nonsyndromic oral clefts and 12 genes (CLPTM1, CRISPLD2, FGFR2, GABRB3, GLI2, IRF6, PTCH1, RARA, RYK, SATB2, SUMO1, TGFA) could be confirmed.
Thirty-one single nucleotide polymorphisms (SNPs) in exons, splice sites, and conserved non-coding regions were studied in 509 patients with cleft lip with or without cleft palate (CLP), 383 with cleft palate only (CP), 838 mothers and 719 fathers of patients with oral clefts, and 902 controls from Ireland. Case-control and family-based statistical tests were performed using isolated oral clefts for the main analyses.
In case-control comparisons, the minor allele of PTCH1 A562A (rs2066836) was associated with reduced odds of CLP (OR: 0.29, 95% CI: 0.13–0.64 for homozygotes) whereas the minor allele of PTCH1 L1315P (rs357564) was associated with increased odds of CLP (OR: 1.36, 95% CI: 1.07–1.74 for heterozygotes and OR: 1.56, 95% CI: 1.09–2.24 for homozygotes). The minor allele of one SUMO1 SNP, rs3769817 located in intron 2, was associated with increased odds of CP (OR: 1.45, 95% CI: 1.06–1.99 for heterozygotes). Transmission disequilibrium was observed for the minor allele of TGFA V159V (rs2166975) which was over-transmitted to CP cases (P=0.041).
For 10 of the 12 genes, this is the largest candidate gene study of nonsyndromic oral clefts to date. The findings provide further evidence that PTCH1, SUMO1, and TGFA contribute to nonsyndromic oral clefts.
cleft lip; cleft palate; congenital abnormalities
A patient with a homozygous premature stop codon in PIK3R1 showed an early developmental block in B cell development but minimal effects in other organ systems.
Whole exome sequencing was used to determine the causative gene in patients with B cell defects of unknown etiology. A homozygous premature stop codon in exon 6 of PIK3R1 was identified in a young woman with colitis and absent B cells. The mutation results in the absence of p85α but normal expression of the p50α and p55α regulatory subunits of PI3K. Bone marrow aspirates from the patient showed <0.1% CD19+ B cells with normal percentages of TdT+VpreB+CD19− B cell precursors. This developmental block is earlier than that seen in patients with defects in the B cell receptor signaling pathway or in a strain of engineered mice with a similar defect in p85α. The number and function of the patient’s T cells were normal. However, Western blot showed markedly decreased p110δ, as well as absent p85α, in patient T cells, neutrophils, and dendritic cells. The patient had normal growth and development and normal fasting glucose and insulin. Mice with p85α deficiency have insulin hypersensitivity, defective platelet function, and abnormal mast cell development. In contrast, the absence of p85α in the patient results in an early and severe defect in B cell development but minimal findings in other organ systems.
Neural tube defects (NTDs) are common birth defects (~1 in 1000 pregnancies in the US and Europe) that have complex origins, including environmental and genetic factors. A low level of maternal folate is one well-established risk factor, with maternal periconceptional folic acid supplementation reducing the occurrence of NTD pregnancies by 50-70%. Gene variants in the folate metabolic pathway (e.g., MTHFR rs1801133 (677 C > T) and MTHFD1 rs2236225 (R653Q)) have been found to increase NTD risk. We hypothesized that variants in additional folate/B12 pathway genes contribute to NTD risk.
A tagSNP approach was used to screen common variation in 82 candidate genes selected from the folate/B12 pathway and NTD mouse models. We initially genotyped polymorphisms in 320 Irish triads (NTD cases and their parents), including 301 cases and 341 Irish controls to perform case–control and family based association tests. Significantly associated polymorphisms were genotyped in a secondary set of 250 families that included 229 cases and 658 controls. The combined results for 1441 SNPs were used in a joint analysis to test for case and maternal effects.
Nearly 70 SNPs in 30 genes were found to be associated with NTDs at the p < 0.01 level. The ten strongest association signals (p-value range: 0.0003–0.0023) were found in nine genes (MFTC, CDKN2A, ADA, PEMT, CUBN, GART, DNMT3A, MTHFD1 and T (Brachyury)) and included the known NTD risk factor MTHFD1 R653Q (rs2236225). The single strongest signal was observed in a new candidate, MFTC rs17803441 (OR = 1.61 [1.23-2.08], p = 0.0003 for the minor allele). Though nominally significant, these associations did not remain significant after correction for multiple hypothesis testing.
To our knowledge, with respect to sample size and scope of evaluation of candidate polymorphisms, this is the largest NTD genetic association study reported to date. The scale of the study and the stringency of correction are likely to have contributed to real associations failing to survive correction. We have produced a ranked list of variants with the strongest association signals. Variants in the highest rank of associations are likely to include true associations and should be high priority candidates for further study of NTD risk.
Neural tube defects; Spina bifida; Folic acid; One-carbon metabolism; Candidate gene
Periconceptional use of folic acid prevents most neural tube defects (NTDs). Whether folic acid and/or multivitamins can prevent other congenital anomalies is not clear. This study tested whether maternal blood levels of folate and vitamin B12 in pregnancies affected by congenital malformations excluding NTDs are lower when compared to non-affected pregnancies.
We measured pregnancy red cell folate (RCF), vitamin B12, and homocysteine (tHcy) concentrations in blood samples taken at the first antenatal clinic in Dublin maternity hospitals in 1986–1990 when vitamin supplementation was rare. The cases were mothers who delivered a baby with a congenital malformation other than NTD identified by the Dublin EUROCAT Registry; controls were a systematic sample of mothers of offspring without congenital malformations from the same hospitals in the same time period.
The median maternal levels of RCF and tHcy did not differ significantly between cases and controls for any of the congenital malformation groups examined (RCF: all malformations 275.9 ug/L v controls 271.2; p=0.77; tHcy: all malformations 7.5 umol/L v controls 7.6; p=0.57). In an unadjusted analysis vitamin B12 was significantly higher in case-mothers whose babies had cleft palate only (p=0.006), musculoskeletal malformations (p=0.034) and midline defects (p=0.039) but not after adjustment for multiple testing.
Our data suggest that low maternal folate and B12 levels or high tHcy levels in early pregnancy are not associated with all congenital malformations excluding NTDs. Fortification with folic acid or B12 may not have a beneficial effect in the prevention of these anomalies.
To study the effect of in-utero alcohol exposure on the insulin-like growth factor axis (IGF) and leptin during infancy and childhood, considering that exposed children may exhibit pre- and postnatal growth retardation.
We prospectively identified heavily drinking pregnant women who consumed on average 4 or more drinks of ethanol per day (≥48 g/day) and assessed growth in 69 of their offspring and an unexposed control group of 83 children, measuring serum IGF-I (radioimmunoassay), IGF-II (immunoradiometric assay, IRMA), insulin-like growth factor-binding protein 3 (IGFBP-3) (IRMA) and leptin (IRMA) at 1 month and 1, 2, 3, 4, and 5 years of age.
IGF-II levels increased with age in both groups, but the rate of increase was significantly higher in exposed children, and levels were significantly higher in ethanol-exposed children at 3, 4, and 5 years of age. In exposed children, IGF-I levels were higher at 3 and 4 years and leptin levels were significantly lower at 1 and 2 years. Exposed subjects showed a much lower correlation between IGF-I and growth parameters than unexposed subjects.
Exposure to ethanol during pregnancy increases IGF-I and IGF-II and decreases leptin during early childhood. The increase in serum IGF-II concentrations in ethanol-exposed children suggests that this hormone should be explored as a potential marker for prenatal alcohol exposure.
Fetal alcohol syndrome; Pregnancy; Alcohol abuse; Insulin-like growth factor I; Insulin-like growth factor II
We report the updated classification of primary immunodeficiency diseases, compiled by the ad hoc Expert Committee of the International Union of Immunological Societies. As compared to the previous edition, more than 15 novel disease entities have been added in the updated version. For each disorders, the key clinical and laboratory features are provided. This updated classification is meant to help in the diagnostic approach to patients with these diseases.
primary immunodeficiency diseases
More than 50 years after Ogdeon Bruton’s discovery of congenital agammaglobulinemia, human primary immunodeficiencies (PIDs) continue to unravel novel molecular and cellular mechanisms that govern development and function of the human immune system. This report provides the updated classification of PIDs, that has been compiled by the International Union of Immunological Societies (IUIS) Expert Committee of Primary Immunodeficiencies after its biannual meeting, in Dublin (Ireland) in June 2009. Since the appearance of the last classification in 2007, novel forms of PID have been discovered, and additional pathophysiology mechanisms that account for PID in humans have been unraveled. Careful analysis and prompt recognition of these disorders is essential to prompt effective forms of treatment and thus to improve survival and quality of life in patients affected with PIDs.
primary immunodeficiencies; T cells; B cells; severe combined immune deficiency; predominantly antibody deficiencies; DNA repair defects; phagocytes; complement; immune dysregulation syndromes; innate immunity; autoinflammatory disorders
This study was designed to provide more detailed information on the subcellular sites of binding of the porphycene, termed 9-capronyloxytetrakis (methoxyethyl) porphycene (CPO), with a fluorescence resonance energy transfer (FRET) technique. The proximity of CPO to two fluorescent probes was determined: nonyl acridine orange (NAO), a dye with specific affinity for the mitochondrial lipid cardiolipin, and dihexaoxacarbocyanine iodide (DiOC6), an agent that labels the endoplasmic reticulum (ER). FRET spectra indicated energy transfer between DiOC6 and CPO but no significant transfer between NAO and CPO. These results confirm data obtained by fluorescence microscopy, suggesting a similar pattern of subcellular localization by CPO and DiOC6 but not by CPO and NAO. However, when cells containing CPO were irradiated and then loaded with NAO, FRET between the two fluorophores was observed. Hence, a relocalization of CPO can occur during irradiation. These data provide an explanation for recent studies on CPO-catalyzed photodamage to both ER and mitochondrial Bcl-2.
In the past, immunodeficiencies were categorized based on clinical and laboratory findings in the affected patient. Now we are more likely to define them based on the specific gene involved. One might expect this shift to increase the precision and clarity of diagnosis but in the last few years it has become increasingly clear that identification of a mutation in a specific gene may not tell the whole story. Some gene defects may reliably result in clinical disease, others may act as susceptibility factors that are more common in patients with immunodeficiency but can also be found in otherwise healthy individuals. Distinguishing between these two types of gene defects is essential for informative genetic counseling.
Genetic and environmental factors contribute to the etiology of neural tube defects (NTDs). While periconceptional folic acid supplementation is known to significantly reduce the risk of NTDs, folate metabolic pathway related factors do not account for all NTDs. Evidence from mouse models indicates that the tumor protein p53 (TP53) is involved in implantation and normal neural tube development. To determine whether genetic variation in the TP53 might contribute to NTD risk in humans, we constructed a high resolution linkage disequilibrium (LD) map of the TP53 genomic region based on genotyping 21 markers in an Irish population. We found that nine of these variants can be used to capture the majority of common variation in the TP53 genomic region. In contrast, the 3-marker haplotype commonly reported in the TP53 literature offers limited coverage of the variation in the gene. We used the expanded set of polymorphisms to measure the influence of TP53 on NTDs using both case-control and family-based tests of association. We also assayed a functional variant in the p53 regulator MDM2 (rs2279744). Alleles of three noncoding TP53 markers were associated with NTD risk. A case effect was seen with the GG genotype of rs1625895 in intron 6 (OR = 1.37 [1.04-1.79], p=0.02). A maternal effect was seen with the 135/135 genotype of the intron 1 VNTR (OR = 1.86 [1.16-2.96], p=0.01) and the TT genotype of rs1614984 (RR = 0.58 [0.37-0.91], p=0.02). As multiple comparisons were made, these cannot be considered definitive positive findings and additional investigation is required.
neural tube defects; spina bifida; p53; TP53; MDM2; linkage disequilibrium
More than 20 North American academic centers account for the majority of hematopoietic stem cell transplantation (HCT) procedures for primary immunodeficiency diseases (PIDs), with smaller numbers performed at additional sites. Given the importance of a timely diagnosis of these rare diseases and the diversity of practice sites, there is a need for guidance as to best practices in management of patients with PIDs before, during, and in follow-up for definitive treatment. In this conference report of immune deficiency experts and HCT physicians who care for patients with PIDs, we present expert guidance for (1) PID diagnoses that are indications for HCT, including severe combined immunodeficiency disease (SCID), combined immunodeficiency disease, and other non-SCID diseases; (2) the critical importance of a high degree of suspicion of the primary care physician and timeliness of diagnosis for PIDs; (3) the need for rapid referral to an immune deficiency expert, center with experience in HCT, or both for patients with PIDs; (4) medical management of a child with suspicion of SCID/combined immunodeficiency disease while confirming the diagnosis, including infectious disease management and workup; (5) the posttransplantation follow-up visit schedule; (6) antimicrobial prophylaxis after transplantation, including gamma globulin administration; and (7) important indications for return to the transplantation center after discharge. Finally, we discuss the role of high-quality databases in treatment of PIDs and HCTas an element of the infrastructure that will be needed for productive multicenter clinical trials in these rare diseases.
Allogeneic hematopoietic stem cell transplantation; gene therapy; primary immunodeficiency; clinical trial