Hyper-IgM syndrome (HIGM) is a rare immunodeficiency phenotype that is usually accompanied by serious infections. We present a curious case of the incidental detection of HIGM in a 45-year-old male with complement C1q deficiency. He had relatively mild sinopulmonary infections, recurrent skin infections and lipomas in his adulthood. Investigations revealed normal enumeration of total peripheral blood B cells and reduced expression of CD40L on his CD4(+) T cells. C1q was noted to be absent, due to a peripheral inhibitor such as an autoantibody. Genomic sequencing of the patient and his parents revealed a novel, de novo heterozygous mutation in the ATM (ataxia telangiectasia mutated) gene although he displayed no clinical evidence of ataxia telangiectasia. This is a rare case of HIGM and acquired C1q deficiency. We present full phenotyping data that contributes to the growing understanding to these interesting immunodeficiencies.

ABSTRACTHyper-IgM syndrome (HIGM) is a rare immunodeficiency phenotype that is usually accompanied by serious infections. We present a curious case of the incidental detection of HIGM in a 45-year-old male with complement C1q deficiency. He had relatively mild sinopulmonary infections, recurrent skin infections and lipomas in his adulthood. Investigations revealed normal enumeration of total peripheral blood B cells and reduced expression of CD40L on his CD4+ T cells. C1q was noted to be absent, due to a peripheral inhibitor such as an autoantibody. Genomic sequencing of the patient and his parents revealed a novel, de novo heterozygous mutation in the ATM (ataxia telangiectasia mutated) gene although he displayed no clinical evidence of ataxia telangiectasia. This is a rare case of HIGM and acquired C1q deficiency. We present full phenotyping data that contributes to the growing understanding to these interesting immunodeficiencies.

P62: RAPID TRANSITION OF PATIENTS ON INTRAVENOUS IMMUNOGLOBULIN REPLACEMENT TO SUBCUTANEOUS IMMUNOGLOBULIN REPLACEMENT IS FEASIBLE AND LEADS TO IMPROVED HEALTH ECONOMICS Suran Fernando, Philippa Weaver, Reina Zaragoza, Vera Cvetanovski, Jamma Li Department of Clinical Immunology and Allergy, Royal North Shore Hospital, Sydney, New South Wales, AustraliaUniversity of Sydney, Sydney, New South Wales, AustraliaPatient Safety and Quality Unit, Royal North Shore Hospital, Sydney, New South Wales, Australia

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is common, with a prevalence of 1/1000 and predominantly caused by disease-causing variants in PKD1 or PKD2. Clinical diagnosis is usually by age-dependent imaging criteria, which is challenging in patients with atypical clinical features, without family history, or younger age. However, there is increasing need for definitive diagnosis of ADPKD with new treatments available. Sequencing is complicated by six pseudogenes that share 97% homology to PKD1 and by recently identified phenocopy genes. Whole-genome sequencing can definitively diagnose ADPKD, but requires validation for clinical use. We initially performed a validation study, in which 42 ADPKD patients underwent sequencing of PKD1 and PKD2 by both whole-genome and Sanger sequencing, using a blinded, cross-over method. Whole-genome sequencing identified all PKD1 and PKD2 germline pathogenic variants in the validation study (sensitivity and specificity 100%). Two mosaic variants outside pipeline thresholds were not detected. We then examined the first 144 samples referred to a clinically-accredited diagnostic laboratory for clinical whole-genome sequencing, with targeted-analysis to a polycystic kidney disease gene-panel. In this unselected, diagnostic cohort (71 males :73 females), the diagnostic rate was 70%, including a diagnostic rate of 81% in patients with typical ADPKD (98% with PKD1/PKD2 variants) and 60% in those with atypical features (56% PKD1/PKD2; 44% PKHD1/HNF1B/GANAB/ DNAJB11/PRKCSH/TSC2). Most patients with atypical disease did not have clinical features that predicted likelihood of a genetic diagnosis. These results suggest clinicians should consider diagnostic genomics as part of their assessment in polycystic kidney disease, particularly in atypical disease.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Variants in the NR5A1 gene encoding SF1 have been described in a diverse spectrum of disorders of sex development (DSD). Recently, we reported the use of a targeted gene panel for DSD where we identified 15 individuals with a variant in NR5A1, nine of which are novel. Here, we examine the functional effect of these changes in relation to the patient phenotype. All novel variants tested had reduced trans‐activational activity, while several had altered protein level, localization, or conformation. In addition, we found evidence of new roles for SF1 protein domains including a region within the ligand binding domain that appears to contribute to SF1 regulation of Müllerian development. There was little correlation between the severity of the phenotype and the nature of the NR5A1 variant. We report two familial cases of NR5A1 deficiency with evidence of variable expressivity; we also report on individuals with oligogenic inheritance. Finally, we found that the nature of the NR5A1 variant does not inform patient outcomes (including pubertal androgenization and malignancy risk). This study adds nine novel pathogenic NR5A1 variants to the pool of diagnostic variants. It highlights a greater need for understanding the complexity of SF1 function and the additional factors that contribute.

46,XX disorders of sexual development (DSDs) occur rarely and result from disruptions of the genetic pathways underlying gonadal development and differentiation. We present a case of a young phenotypic male with 46,XX SRY-negative ovotesticular DSD resulting from a duplication upstream of SOX9 presenting with a painful testicular mass resulting from ovulation into an ovotestis. We present a literature review of ovulation in phenotypic men and discuss the role of SRY and SOX9 in testicular development, including the role of SOX9 upstream enhancer region duplication in female-to-male sex reversal.LEARNING POINTS:In mammals, the early gonad is bipotent and can differentiate into either a testis or an ovary. SRY is the master switch in testis determination, responsible for differentiation of the bipotent gonad into testis.SRY activates SOX9 gene, SOX9 as a transcription factor is the second major gene involved in male sex determination. SOX9 drives the proliferation of Sertoli cells and activates AMH/MIS repressing the ovary. SOX9 is sufficient to induce testis formation and can substitute for SRY function.Assessing karyotype and then determination of the presence or absence of Mullerian structures are necessary serial investigations in any case of DSD, except for mixed gonadal dysgenesis identified by karyotype alone.Treatment is ideal in a multidisciplinary setting with considerations to genetic (implications to family and reproductive recurrence risk), psychological aspects (sensitive individualized counseling including patient gender identity and preference), endocrinological (hormone replacement), surgical (cosmetic, prophylactic gonadectomy) fertility preservation and reproductive opportunities and metabolic health (cardiovascular and bones).

Rapid retrospective biodosimetry methods are essential for the fast triage of persons occupationally or accidentally exposed to ionizing radiation. Identification and detection of a radiation specific molecular ‘footprint’ should provide a sensitive and reliable measurement of radiation exposure. Here we discuss conventional (cytogenetic) methods of detection and assessment of radiation exposure in comparison to emerging approaches such as gene expression signatures and DNA damage markers. Furthermore, we provide an overview of technical and logistic details such as type of sample required, time for sample preparation and analysis, ease of use and potential for a high throughput analysis.

A custom CGH microarray that covers the SOX9 regulatory region. Log2 ratio scatterplot showing individual data points. Blue box highlights copy number gain with 3' breakpoint region magnified.

Remarkable progress has been achieved in understanding the mechanisms controlling sex determination, yet the cause for many Disorders of Sex Development (DSD) remains unknown. Of particular interest is a rare XX DSD subtype in which individuals are negative for SRY, the testis determining factor on the Y chromosome, yet develop testes or ovotestes, and both of these phenotypes occur in the same family. This is a naturally occurring disorder in humans (Homo sapiens) and dogs (C. familiaris). Phenotypes in the canine XX DSD model are strikingly similar to those of the human XX DSD subtype. The purposes of this study were to identify 1) a variant associated with XX DSD in the canine model and 2) gene expression alterations in canine embryonic gonads that could be informative to causation. Using a genome wide association study (GWAS) and whole genome sequencing (WGS), we identified a variant on C. familiaris autosome 9 (CFA9) that is associated with XX DSD in the canine model and in affected purebred dogs. This is the first marker identified for inherited canine XX DSD. It lies upstream of SOX9 within the canine ortholog for the human disorder, which resides on 17q24. Inheritance of this variant indicates that XX DSD is a complex trait in which breed genetic background affects penetrance. Furthermore, the homozygous variant genotype is associated with embryonic lethality in at least one breed. Our analysis of gene expression studies (RNA-seq and PRO-seq) in embryonic gonads at risk of XX DSD from the canine model identified significant RSPO1 downregulation in comparison to XX controls, without significant upregulation of SOX9 or other known testis pathway genes. Based on these data, a novel mechanism is proposed in which molecular lesions acting upstream of RSPO1 induce epigenomic gonadal mosaicism.

In the article cited above, there was an error in table 2. The corrected table is listed below. Heterozygous missense mutation Mosaic discovered in the father at 17% penetrance Linkage analysis Single gene sequencing Deletion of SOX3 upstream regulatory region SOX3 duplication FISH Microsatellite analysis Microarray MLPA MLPA CGH Array Mosaic sex chromosome SNV within the HMG domain XY, XX, (XX&XY) (X, XX,XY) FISH CGH Array Point mutations causing premature stop codons and splice site mutations Patients often have 2 SNV occurring together The authors regret this error.