The genomic landscape of breast- and non-breast cancers from individuals with germline CHEK2-deficiency.

CHEK2 is considered to be involved in homologous recombination repair (HRR). Individuals who have germline pathogenic variants (gPVs) in CHEK2 are at increased risk to develop breast cancer and likely other primary cancers. PARP inhibitors (PARPi) have been shown to be effective in the treatment of cancers that present with HRR-deficiency, for example caused by inactivation of BRCA1/2. However, clinical trials have shown little-to-no efficacy of PARPi in patients with CHEK2 gPVs. Here, we show that both breast and non-breast cancers from individuals who have biallelic gPVs in CHEK2 (germline CHEK2-deficiency) do not present with molecular profiles that fit with HRR-deficiency. This finding provides a likely explanation why PARPi therapy is not successful in the treatment of CHEK2-deficient cancers.

Histopathological phenotyping of cancers in PTEN Hamartoma Tumor Syndrome for improved recognition: A single-center study.

PTEN hamartoma tumor syndrome (PHTS) has a broad clinical spectrum including various benign and malignant tumors at varying age of diagnosis. Many patients remain unrecognized, unaware of their increased cancer risk. We aimed to describe the cancer spectrum, age of onset and histopathological cancer characteristics to assess whether specific cancer characteristics could improve PHTS recognition. Genetic testing results and pathology reports were collected for patients tested for germline PTEN variants between 1997 and 2020 from the diagnostic laboratory and the Dutch nationwide pathology databank (Palga). The cancer spectrum and age of onset were assessed in patients with (PTENpos) and without (PTENneg) a germline PTEN variant. Histopathological cancer characteristics were assessed in a nested cohort. 341 PTENpos patients (56% females) and 2882 PTENneg patients (66% females) were included. PTENpos patients presented mostly with female breast (BC, 30%), endometrial (EC, 6%), thyroid (TC, 4%) or colorectal cancer (4%). PTENpos were significantly younger at cancer onset (43 vs. 47 years) and had more often (46% vs. 18%) a second BC than PTENneg. PTEN detection rates were highest for BC <40 years (9%), TC <20 years (15%) and EC <50 years (28%), and dropped to 6%, 4%, and 15% by age 60. Histopathological characteristics were similar between groups. No histopathological cancer characteristics were distinctive for PHTS. However, PTENpos were significantly younger at cancer onset. Therefore early-onset BC, EC, or TC warrants consideration of PHTS diagnostics either through a pre-screen for other PHTS features or direct germline testing.

Exploring the Prevalence of Oral Features for Early Detection of PTEN Hamartoma Tumour Syndrome.

AIMS: Patients with PTEN hamartoma tumour syndrome (PHTS) have an increased risk of developing cancer due to a pathogenic germline variant in the PTEN tumour suppressor gene. Early recognition of PHTS facilitates initiation of cancer surveillance which is highly effective in preventing the development of advanced malignancies. PHTS is rare and due to its varied phenotype, even within families, oral abnormalities may be a valuable tool in the identification of these patients at an early stage before cancer development. MATERIALS AND METHODS: Between 1997 and 2020, phenotypic characteristics were evaluated in 81 paediatric (median age: 9 years) and 86 adult (median age: 40 years) PHTS patients by one of 2 medical experts during yearly surveillance visits at a Dutch PHTS expertise centre. Oral features evaluated included gingival hypertrophy, oral papillomas, and high palate (in adults). RESULTS: Within adults, gingival hypertrophy was present in 94%, oral papillomas in 88%, and a high palate in 89%. All adult patients had at least one of these oral features, and 99% showed at least 2 oral features. Oral features were less common in paediatric patients, especially under 11 years of age. Gingival hypertrophy was observed in 44% and oral papillomas in 54% of paediatric patients. CONCLUSIONS: The presence of 2 or 3 oral features may indicate PHTS in adults or adolescents, especially if macrocephaly is present. Dental professionals are well-positioned to recognise these oral manifestations could be related to PHTS. They can initiate an overall clinical assessment of the patient by alerting the patient's medical practitioner of the findings and the possible need for genetic testing. This could significantly improve outcomes, including life expectancy, for patients and possibly for their relatives. CLINICAL RELEVANCE: Dental professionals are ideally placed to recognise oral features and initiate early assessment of PHTS which could significantly improve patient outcomes.

Prevalence of comorbidities in individuals with neurodevelopmental disorders from the aggregated phenomics data of 51,227 pediatric individuals.

The prevalence of comorbidities in individuals with neurodevelopmental disorders (NDDs) is not well understood, yet these are important for accurate diagnosis and prognosis in routine care and for characterizing the clinical spectrum of NDD syndromes. We thus developed PhenomAD-NDD, an aggregated database containing the comorbid phenotypic data of 51,227 individuals with NDD, all harmonized into Human Phenotype Ontology (HPO), with in total 3,054 unique HPO terms. We demonstrate that almost all congenital anomalies are more prevalent in the NDD population than in the general population, and the NDD baseline prevalence allows for an approximation of the enrichment of symptoms. For example, such analyses of 33 genetic NDDs show that 32% of enriched phenotypes are currently not reported in the clinical synopsis in the Online Mendelian Inheritance in Man (OMIM). PhenomAD-NDD is open to all via a visualization online tool and allows us to determine the enrichment of symptoms in NDD.

Lifestyle Factors and Breast Cancer in Females with PTEN Hamartoma Tumor Syndrome (PHTS).

Females with PTEN Hamartoma Tumor Syndrome (PHTS) have breast cancer risks up to 76%. This study assessed associations between breast cancer and lifestyle in European female adult PHTS patients. Data were collected via patient questionnaires (July 2020-March 2023) and genetic diagnoses from medical files. Associations between lifestyle and breast cancer were calculated using logistic regression corrected for age. Index patients with breast cancer before PHTS diagnosis (breast cancer index) were excluded for ascertainment bias correction. In total, 125 patients were included who completed the questionnaire at a mean age of 44 years (SD = 13). This included 21 breast cancer indexes (17%) and 39 females who developed breast cancer at 43 years (SD = 9). Breast cancer patients performed about 1.1 times less often 0-1 times/week physical activity than ≥2 times (ORtotal-adj = 0.9 (95%CI 0.3-2.6); consumed daily about 1.2-1.8 times more often ≥1 than 0-1 glasses of alcohol (ORtotal-adj = 1.2 (95%CI 0.4-4.0); ORnon-breastcancer-index-adj = 1.8 (95%CI 0.4-6.9); were about 1.04-1.3 times more often smokers than non-smokers (ORtotal-adj = 1.04 (95%CI 0.4-2.8); ORnon-breastcancer-index-adj = 1.3 (95%CI 0.4-4.2)); and overweight or obesity (72%) was about 1.02-1.3 times less common (ORtotal-adj = 0.98 (95%CI 0.4-2.6); ORnon-breastcancer-index-adj = 0.8 (95%CI 0.3-2.7)). Similar associations between lifestyle and breast cancer are suggested for PHTS and the general population. Despite not being statistically significant, results are clinically relevant and suggest that awareness of the effects of lifestyle on patients' breast cancer risk is important.

Expanding the PRAAS spectrum: De novo mutations of immunoproteasome subunit ß-type 10 in six infants with SCID-Omenn syndrome.

Mutations in proteasome ß-subunits or their chaperone and regulatory proteins are associated with proteasome-associated autoinflammatory disorders (PRAAS). We studied six unrelated infants with three de novo heterozygous missense variants in PSMB10, encoding the proteasome ß2i-subunit. Individuals presented with T-B-NK± severe combined immunodeficiency (SCID) and clinical features suggestive of Omenn syndrome, including diarrhea, alopecia, and desquamating erythematous rash. Remaining T cells had limited T cell receptor repertoires, a skewed memory phenotype, and an elevated CD4/CD8 ratio. Bone marrow examination indicated severely impaired B cell maturation with limited V(D)J recombination. All infants received an allogeneic stem cell transplant and exhibited a variety of severe inflammatory complications thereafter, with 2 peri-transplant and 2 delayed deaths. The single long-term transplant survivor showed evidence for genetic rescue through revertant mosaicism overlapping the affected PSMB10 locus. The identified variants (c.166G>C [p.Asp56His] and c.601G>A/c.601G>C [p.Gly201Arg]) were predicted in silico to profoundly disrupt 20S immunoproteasome structure through impaired ß-ring/ß-ring interaction. Our identification of PSMB10 mutations as a cause of SCID-Omenn syndrome reinforces the connection between PRAAS-related diseases and SCID.

The heterogeneous cancer phenotype of individuals with biallelic germline pathogenic variants in CHEK2.

PURPOSE: Females with biallelic CHEK2 germline pathogenic variants (gPVs) more often develop multiple breast cancers than individuals with monoallelic CHEK2 gPVs. This study is aimed at expanding the knowledge on the occurrence of other malignancies. METHODS: Exome sequencing of individuals who developed multiple primary malignancies identified 3 individuals with the CHEK2 (NM_007194.4) c.1100del p.(Thr367MetfsTer15) loss-of-function gPV in a biallelic state. We collected the phenotypes of an additional cohort of individuals with CHEK2 biallelic gPVs (n = 291). RESULTS: In total, 157 individuals (53.4%; 157/294 individuals) developed ≥1 (pre)malignancy. The most common (pre)malignancies next to breast cancer were colorectal- (n = 19), thyroid- (n = 19), and prostate (pre)malignancies (n = 12). Females with biallelic CHEK2 loss-of-function gPVs more frequently developed ≥2 (pre)malignancies and at an earlier age compared with females biallelic for the CHEK2 c.470T>C p.(Ile157Thr) missense variant. Furthermore, 26 males (31%; 26/84 males) with CHEK2 biallelic gPVs developed ≥1 (pre)malignancies of 15 origins. CONCLUSION: Our study suggests that CHEK2 biallelic gPVs likely increase the susceptibility to develop multiple malignancies in various tissues, both in females and males. However, it is possible that a substantial proportion of individuals with CHEK2 biallelic gPVs is missed as diagnostic testing for CHEK2 often is limited to individuals who developed breast cancer.

OTULIN Haploinsufficiency-Related Fasciitis and Skin Necrosis Treated by TNF Inhibition.

Here, we describe an adult female with severe fasciitis and skin necrosis who carried a private, predicted deleterious missense mutation in OTULIN in heterozygosity. OTULIN is a cellular regulator of deubiquitination that has been shown to play a key role in intrinsic immunity against staphylococcal α-toxin. The patient was treated with broad-spectrum antibiotics, and multiple surgical explorations were conducted without clinical response. Since autoinflammation was the predominant clinical feature, TNF inhibition was started with a good clinical response. We show that excessive inflammation in OTULIN haploinsufficiency can be effectively treated by TNF inhibition.

PhenoScore quantifies phenotypic variation for rare genetic diseases by combining facial analysis with other clinical features using a machine-learning framework.

Several molecular and phenotypic algorithms exist that establish genotype-phenotype correlations, including facial recognition tools. However, no unified framework that investigates both facial data and other phenotypic data directly from individuals exists. We developed PhenoScore: an open-source, artificial intelligence-based phenomics framework, combining facial recognition technology with Human Phenotype Ontology data analysis to quantify phenotypic similarity. Here we show PhenoScore's ability to recognize distinct phenotypic entities by establishing recognizable phenotypes for 37 of 40 investigated syndromes against clinical features observed in individuals with other neurodevelopmental disorders and show it is an improvement on existing approaches. PhenoScore provides predictions for individuals with variants of unknown significance and enables sophisticated genotype-phenotype studies by testing hypotheses on possible phenotypic (sub)groups. PhenoScore confirmed previously known phenotypic subgroups caused by variants in the same gene for SATB1, SETBP1 and DEAF1 and provides objective clinical evidence for two distinct ADNP-related phenotypes, already established functionally.

Molecular mechanism of extracutaneous tumours in patients with basal cell nevus syndrome.

Basal cell nevus syndrome (BCNS) is a rare genetic disorder accompanied by a broad variety of tumours, of which basal cell carcinomas and odontogenic keratocysts are the most common. BCNS is caused by a germline or postzygotic mutation in either PTCH1 or SUFU As BCNS is a rare disease, it is difficult to establish whether less frequently occurring tumours are actually part of the syndrome. In this study, the molecular mechanism behind four extracutaneous tumours in patients with BCNS was elucidated. A leiomyoma of the testis and meningioma were confirmed to be associated with BCNS in two patients by presence of a second mutation or loss of heterozygosity in PTCH1 In a meningioma of a patient with a mosaic postzygotic PTCH1 mutation an association could not be conclusively confirmed. SUFU was probably not involved in the development of a thyroid carcinoma in a patient with a germline SUFU mutation. Hence, we have proven that meningioma and leiomyoma of the testis are rare extracutaneous tumours that are part of BCNS.

Cancer risks by sex and variant type in PTEN hamartoma tumor syndrome.

BACKGROUND: PTEN Hamartoma Tumor Syndrome (PHTS) is a rare syndrome with a broad phenotypic spectrum, including increased risks of breast (BC, 67%-78% at age 60 years), endometrial (EC, 19%-28%), and thyroid cancer (TC, 6%-38%). Current risks are likely overestimated due to ascertainment bias. We aimed to provide more accurate and personalized cancer risks. METHODS: This was a European, adult PHTS cohort study with data from medical files, registries, and/or questionnaires. Cancer risks and hazard ratios were assessed with Kaplan-Meier and Cox regression analyses, and standardized incidence ratios were calculated. Bias correction consisted of excluding cancer index cases and incident case analyses. RESULTS: A total of 455 patients were included, including 50.5% index cases, 372 with prospective follow-up (median 6 years, interquartile range = 3-10 years), and 159 of 281 females and 39 of 174 males with cancer. By age 60 years, PHTS-related cancer risk was higher in females (68.4% to 86.3%) than males (16.4% to 20.8%). Female BC risks ranged from 54.3% (95% confidence interval [CI] = 43.0% to 66.4%) to 75.8% (95% CI = 60.7% to 88.4%), with two- to threefold increased risks for PTEN truncating and approximately twofold for phosphatase domain variants. EC risks ranged from 6.4% (95% CI = 2.1% to 18.6%) to 22.1% (95% CI = 11.6% to 39.6%) and TC risks from 8.9% (95% CI = 5.1% to 15.3%) to 20.5% (95% CI = 11.3% to 35.4%). Colorectal cancer, renal cancer, and melanoma risks were each less than 10.0%. CONCLUSIONS: Females have a different BC risk depending on their PTEN germline variant. PHTS patients are predominantly at risk of BC (females), EC, and TC. This should be the main focus of surveillance. These lower, more unbiased and personalized risks provide guidance for optimized cancer risk management.

Trio-based whole exome sequencing in patients with suspected sporadic inborn errors of immunity: A retrospective cohort study.

Background: De novo variants (DNVs) are currently not routinely evaluated as part of diagnostic whole exome sequencing (WES) analysis in patients with suspected inborn errors of immunity (IEI). Methods: This study explored the potential added value of systematic assessment of DNVs in a retrospective cohort of 123 patients with a suspected sporadic IEI that underwent patient-parent trio-based WES. Results: A (likely) molecular diagnosis for (part) of the immunological phenotype was achieved in 12 patients with the diagnostic in silico IEI WES gene panel. Systematic evaluation of rare, non-synonymous DNVs in coding or splice site regions led to the identification of 14 candidate DNVs in genes with an annotated immune function. DNVs were found in IEI genes (NLRP3 and RELA) and in potentially novel candidate genes, including PSMB10, DDX1, KMT2C, and FBXW11. The FBXW11 canonical splice site DNV was shown to lead to defective RNA splicing, increased NF-κB p65 signalling, and elevated IL-1ß production in primary immune cells extracted from the patient with autoinflammatory disease. Conclusions: Our findings in this retrospective cohort study advocate the implementation of trio-based sequencing in routine diagnostics of patients with sporadic IEI. Furthermore, we provide functional evidence supporting a causal role for FBXW11 loss-of-function mutations in autoinflammatory disease. Funding: This research was supported by grants from the European Union, ZonMW and the Radboud Institute for Molecular Life Sciences.

Genotype-phenotype associations in a large PTEN Hamartoma Tumor Syndrome (PHTS) patient cohort.

BACKGROUND: Pathogenic PTEN germline variants cause PTEN Hamartoma Tumor Syndrome (PHTS), a rare disease with a variable genotype and phenotype. Knowledge about these spectra and genotype-phenotype associations could help diagnostics and potentially lead to personalized care. Therefore, we assessed the PHTS genotype and phenotype spectrum in a large cohort study. METHODS: Information was collected of 510 index patients with pathogenic or likely pathogenic (LP/P) PTEN variants (n = 467) or variants of uncertain significance. Genotype-phenotype associations were assessed using logistic regression analyses adjusted for sex and age. RESULTS: At time of genetic testing, the majority of children (n = 229) had macrocephaly (81%) or developmental delay (DD, 61%), and about half of the adults (n = 238) had cancer (51%), macrocephaly (61%), or cutaneous pathology (49%). Across PTEN, 268 LP/P variants were identified, with exon 5 as hotspot. Missense variants (n = 161) were mainly located in the phosphatase domain (PD, 90%) and truncating variants (n = 306) across all domains. A trend towards 2 times more often truncating variants was observed in adults (OR = 2.3, 95%CI = 1.5-3.4) and patients with cutaneous pathology (OR = 1.6, 95%CI = 1.1-2.5) or benign thyroid pathology (OR = 2.0, 95%CI = 1.1-3.5), with trends up to 2-4 times more variants in PD. Whereas patients with DD (OR = 0.5, 95%CI = 0.3-0.9) or macrocephaly (OR = 0.6, 95%CI = 0.4-0.9) had about 2 times less often truncating variants compared to missense variants. In DD patients these missense variants were often located in domain C2. CONCLUSION: The PHTS phenotypic diversity may partly be explained by the PTEN variant coding effect and the combination of coding effect and domain. PHTS patients with early-onset disease often had missense variants, and those with later-onset disease often truncating variants.

Catch them if you are aware: PTEN postzygotic mosaicism in clinically suspicious patients with PTEN Hamartoma Tumour Syndrome and literature review.

PTEN germline variants cause PTEN Hamartoma Tumour Syndrome (PHTS). Of individuals fulfilling diagnostic criteria, 41-88% test negative for PTEN germline variants, while mosaicism could be an explanation. Here we describe two individuals with PTEN mosaicism. First, a 21-year-old female presented with macrocephaly and a venous malformation. Next generation sequencing analysis on her venous malformation identified the mosaic pathogenic PTEN variant c.493-2A>G (23%). This variant was initially missed in blood due to low frequency (<1%), but detected in buccal swab (21%). Second, a 13-year-old male presented with macrocephaly, language developmental delay, behavioral problems, and an acral hyperkeratotic papule. Targeted PTEN analysis identified the mosaic pathogenic variant c.284C>T (11%) in blood, which was confirmed via buccal swab. These two cases suggest that PTEN mosaicism might be more common than currently reported. PTEN mosaicism awareness is important to enable diagnosis, which facilitates timely inclusion in cancer surveillance programs improving prognosis and life expectancy.

Red flags for early recognition of adult patients with PTEN Hamartoma Tumour Syndrome.

Patients with PTEN Hamartoma Tumour Syndrome (PHTS) are at increased risk of developing cancer. Many adult PHTS patients are not recognized as such and do not receive the cancer surveillance they need. Our aim was to define phenotypic characteristics that can easily be assessed and manifest by early adulthood, and hence could serve as red flags (i.e. alerting signals) for early recognition of adult patients at high risk of PHTS. Phenotypic characteristics including macrocephaly, multinodular goitre (MNG), and oral features were examined in 81 paediatric and 86 adult PHTS patients by one of two medical experts during yearly surveillance visits at our Dutch PHTS expert centre between 1997 and 2020. MNG was defined as signs of thyroid nodules and/or goitre. Oral features included gingival hypertrophy, high palate (adults only) and oral papillomas. Based on the characteristics' prevalence in different age groups, combinations of phenotypic characteristics were defined and evaluated on their potential to recognize individuals with PHTS. Macrocephaly was present in 100% of paediatric and 67% of adult patients. The prevalence of MNG was ∼50% in paediatric and gradually increased to >90% in adult patients. Similar percentages were observed for any of the oral features. Scoring two out of three of these characteristics yielded a sensitivity of 100% (95%CI 94-100%) in adults. The presence of the combination macrocephaly, MNG, or multiple oral features could serve as a red flag for general practitioners, medical specialists, and dentists to consider further assessment of the diagnosis PHTS in adults. In this way, recognition of adult PHTS patients might be improved and cancer surveillance can be offered timely.

Genetic Screening for TLR7 Variants in Young and Previously Healthy Men With Severe COVID-19.

Introduction: Loss-of-function TLR7 variants have been recently reported in a small number of males to underlie strong predisposition to severe COVID-19. We aimed to determine the presence of these rare variants in young men with severe COVID-19. Methods: We prospectively studied males between 18 and 50 years-old without predisposing comorbidities that required at least high-flow nasal oxygen to treat COVID-19. The coding region of TLR7 was sequenced to assess the presence of potentially deleterious variants. Results: TLR7 missense variants were identified in two out of 14 patients (14.3%). Overall, the median age was 38 (IQR 30-45) years. Both variants were not previously reported in population control databases and were predicted to be damaging by in silico predictors. In a 30-year-old patient a maternally inherited variant [c.644A>G; p.(Asn215Ser)] was identified, co-segregating in his 27-year-old brother who also contracted severe COVID-19. A second variant [c.2797T>C; p.(Trp933Arg)] was found in a 28-year-old patient, co-segregating in his 24-year-old brother who developed mild COVID-19. Functional testing of this variant revealed decreased type I and II interferon responses in peripheral mononuclear blood cells upon stimulation with the TLR7 agonist imiquimod, confirming a loss-of-function effect. Conclusions: This study supports a rationale for the genetic screening for TLR7 variants in young men with severe COVID-19 in the absence of other relevant risk factors. A diagnosis of TLR7 deficiency could not only inform on treatment options for the patient, but also enables pre-symptomatic testing of at-risk male relatives with the possibility of instituting early preventive and therapeutic interventions.

Genotype-phenotype correlations and novel molecular insights into the DHX30-associated neurodevelopmental disorders.

BACKGROUND: We aimed to define the clinical and variant spectrum and to provide novel molecular insights into the DHX30-associated neurodevelopmental disorder. METHODS: Clinical and genetic data from affected individuals were collected through Facebook-based family support group, GeneMatcher, and our network of collaborators. We investigated the impact of novel missense variants with respect to ATPase and helicase activity, stress granule (SG) formation, global translation, and their effect on embryonic development in zebrafish. SG formation was additionally analyzed in CRISPR/Cas9-mediated DHX30-deficient HEK293T and zebrafish models, along with in vivo behavioral assays. RESULTS: We identified 25 previously unreported individuals, ten of whom carry novel variants, two of which are recurrent, and provide evidence of gonadal mosaicism in one family. All 19 individuals harboring heterozygous missense variants within helicase core motifs (HCMs) have global developmental delay, intellectual disability, severe speech impairment, and gait abnormalities. These variants impair the ATPase and helicase activity of DHX30, trigger SG formation, interfere with global translation, and cause developmental defects in a zebrafish model. Notably, 4 individuals harboring heterozygous variants resulting either in haploinsufficiency or truncated proteins presented with a milder clinical course, similar to an individual harboring a de novo mosaic HCM missense variant. Functionally, we established DHX30 as an ATP-dependent RNA helicase and as an evolutionary conserved factor in SG assembly. Based on the clinical course, the variant location, and type we establish two distinct clinical subtypes. DHX30 loss-of-function variants cause a milder phenotype whereas a severe phenotype is caused by HCM missense variants that, in addition to the loss of ATPase and helicase activity, lead to a detrimental gain-of-function with respect to SG formation. Behavioral characterization of dhx30-deficient zebrafish revealed altered sleep-wake activity and social interaction, partially resembling the human phenotype. CONCLUSIONS: Our study highlights the usefulness of social media to define novel Mendelian disorders and exemplifies how functional analyses accompanied by clinical and genetic findings can define clinically distinct subtypes for ultra-rare disorders. Such approaches require close interdisciplinary collaboration between families/legal representatives of the affected individuals, clinicians, molecular genetics diagnostic laboratories, and research laboratories.

Beyond nephronophthisis: Retinal dystrophy in the absence of kidney dysfunction in childhood expands the clinical spectrum of CEP83 deficiency.

The CEP83 protein is an essential part in the first steps of ciliogenesis, causing a ciliopathy if deficient. As a core component of the distal appendages of the centriole, CEP83 is located in almost all cell types and is involved in the primary cilium assembly. Previously reported CEP83 deficient patients all presented with nephronophthisis and kidney dysfunction. Despite retinal degeneration being a common feature in ciliopathies, only one patient also had retinitis. Here, we present two unrelated patients, who both presented with retinitis pigmentosa, without nephronophthisis or any form of kidney dysfunction. Both patients harbor bi-allelic variants in CEP83. This report expands the current clinical spectrum of CEP83 deficiency. For timely diagnosis of CEP83 deficiency, we advocate that CEP83 should be included in gene panels for inherited retinal diseases.

Complement factor D haplodeficiency is associated with a reduced complement activation speed and diminished bacterial killing.

OBJECTIVES: Complete deficiency of alternative pathway (AP) complement factors, explained by homozygous mutations, is a well-known risk factor for invasive bacterial infections; however, this is less obvious for heterozygous mutations. We describe two siblings with a heterozygous NM_001928.3(CFD):c.125C>A p.(Ser42*) mutation in the complement factor D (fD) gene having a history of recurrent bacterial infections. We determined the effect of heterozygous fD deficiency on AP complement activity. METHODS: We determined the effect of fD levels on complement activation as measured by AP activity, complement C3 binding to the bacterial surface of Neisseria meningitidis (Nm), Streptococcus pneumoniae (Sp) and non-typeable Haemophilus influenzae (NTHi), and complement-mediated killing of Nm and NTHi. In addition, we measured the effect of vaccination of complement C3 binding to the bacterial surface and killing of Nm. RESULTS: Reconstitution of fD-deficient serum with fD increased AP activity in a dose- and time-dependent way. Reconstitution of patient serum with fD to normal levels increased complement C3 binding to Sp, Nm and NTHi, as well as complement-mediated killing of Nm and NTHi. Vaccination increased complement C3 binding and resulted in complete killing of Nm without fD reconstitution. CONCLUSION: We conclude that low fD serum levels (< 0.5 µg mL-1) lead to a reduced speed of complement activation, which results in diminished bacterial killing, consistent with recurrent bacterial infections observed in our index patients. Specific antibodies induced by vaccination are able to overcome the diminished bacterial killing capacity in patients with low fD levels.