A syndromic neurodevelopmental disorder caused by rare variants in PPFIA3.

PPFIA3 encodes the protein-tyrosine phosphatase, receptor-type, F-polypeptide-interacting-protein-alpha-3 (PPFIA3), which is a member of the LAR-protein-tyrosine phosphatase-interacting-protein (liprin) family involved in synapse formation and function, synaptic vesicle transport, and presynaptic active zone assembly. The protein structure and function are evolutionarily well conserved, but human diseases related to PPFIA3 dysfunction are not yet reported in OMIM. Here, we report 20 individuals with rare PPFIA3 variants (19 heterozygous and 1 compound heterozygous) presenting with developmental delay, intellectual disability, hypotonia, dysmorphisms, microcephaly or macrocephaly, autistic features, and epilepsy with reduced penetrance. Seventeen unique PPFIA3 variants were detected in 18 families. To determine the pathogenicity of PPFIA3 variants in vivo, we generated transgenic fruit flies producing either human wild-type (WT) PPFIA3 or five missense variants using GAL4-UAS targeted gene expression systems. In the fly overexpression assays, we found that the PPFIA3 variants in the region encoding the N-terminal coiled-coil domain exhibited stronger phenotypes compared to those affecting the C-terminal region. In the loss-of-function fly assay, we show that the homozygous loss of fly Liprin-α leads to embryonic lethality. This lethality is partially rescued by the expression of human PPFIA3 WT, suggesting human PPFIA3 function is partially conserved in the fly. However, two of the tested variants failed to rescue the lethality at the larval stage and one variant failed to rescue lethality at the adult stage. Altogether, the human and fruit fly data reveal that the rare PPFIA3 variants are dominant-negative loss-of-function alleles that perturb multiple developmental processes and synapse formation.

Clinical features, functional consequences, and rescue pharmacology of missense GRID1 and GRID2 human variants.

GRID1 and GRID2 encode the enigmatic GluD1 and GluD2 proteins, which form tetrameric receptors that play important roles in synapse organization and development of the central nervous system. Variation in these genes has been implicated in neurodevelopmental phenotypes. We evaluated GRID1 and GRID2 human variants from the literature, ClinVar, and clinical laboratories and found that many of these variants reside in intolerant domains, including the amino terminal domain of both GRID1 and GRID2. Other conserved regions, such as the M3 transmembrane domain, show different intolerance between GRID1 and GRID2. We introduced these variants into GluD1 and GluD2 cDNA and performed electrophysiological and biochemical assays to investigate the mechanisms of dysfunction of GRID1/2 variants. One variant in the GRID1 distal amino terminal domain resides at a position predicted to interact with Cbln2/Cbln4, and the variant disrupts complex formation between GluD1 and Cbln2, which could perturb its role in synapse organization. We also discovered that, like the lurcher mutation (GluD2-A654T), other rare variants in the GRID2 M3 domain create constitutively active receptors that share similar pathogenic phenotypes. We also found that the SCHEMA schizophrenia M3 variant GluD1-A650T produced constitutively active receptors. We tested a variety of compounds for their ability to inhibit constitutive currents of GluD receptor variants and found that pentamidine potently inhibited GluD2-T649A constitutive channels (IC50 50 nM). These results identify regions of intolerance to variation in the GRID genes, illustrate the functional consequences of GRID1 and GRID2 variants, and suggest how these receptors function normally and in disease.

Clinico-biological refinement of BCL11B-related disorder and identification of an episignature: A series of 20 unreported individuals.

PURPOSE: BCL11B-related disorder (BCL11B-RD) arises from rare genetic variants within the BCL11B gene, resulting in a distinctive clinical spectrum encompassing syndromic neurodevelopmental disorder, with or without intellectual disability, associated with facial features and impaired immune function. This study presents an in-depth clinico-biological analysis of 20 newly reported individuals with BCL11B-RD, coupled with a characterization of genome-wide DNA methylation patterns of this genetic condition. METHODS: Through an international collaboration, clinical and molecular data from 20 individuals were systematically gathered, and a comparative analysis was conducted between this series and existing literature. We further scrutinized peripheral blood DNA methylation profile of individuals with BCL11B-RD, contrasting them with healthy controls and other neurodevelopmental disorders marked by established episignature. RESULTS: Our findings unveil rarely documented clinical manifestations, notably including Rubinstein-Taybi-like facial features, craniosynostosis, and autoimmune disorders, all manifesting within the realm of BCL11B-RD. We refine the intricacies of T cell compartment alterations of BCL11B-RD, revealing decreased levels naive CD4+ T cells and recent thymic emigrants while concurrently observing an elevated proportion of effector-memory expressing CD45RA CD8+ T cells (TEMRA). Finally, a distinct DNA methylation episignature exclusive to BCL11B-RD is unveiled. CONCLUSION: This study serves to enrich our comprehension of the clinico-biological landscape of BCL11B-RD, potentially furnishing a more precise framework for diagnosis and follow-up of individuals carrying pathogenic BCL11B variant. Moreover, the identification of a unique DNA methylation episignature offers a valuable diagnosis tool for BCL11B-RD, thereby facilitating routine clinical practice by empowering physicians to reevaluate variants of uncertain significance within the BCL11B gene.

Family-centred care interventions for children with chronic conditions: A scoping review.

INTRODUCTION: Children with chronic conditions have greater health care needs than the general paediatric population but may not receive care that centres their needs and preferences as identified by their families. Clinicians and researchers are interested in developing interventions to improve family-centred care need information about the characteristics of existing interventions, their development and the domains of family-centred care that they address. We conducted a scoping review that aimed to identify and characterize recent family-centred interventions designed to improve experiences with care for children with chronic conditions. METHODS: We searched Medline, Embase, PsycInfo and Cochrane databases, and grey literature sources for relevant articles or documents published between 1 January 2019 and 11 August 2020 (databases) or 7-20 October 2020 (grey literature). Primary studies with ≥10 participants, clinical practice guidelines and theoretical articles describing family-centred interventions that aimed to improve experiences with care for children with chronic conditions were eligible. Following citation and full-text screening by two reviewers working independently, we charted data covering study characteristics and interventions from eligible reports and synthesized interventions by domains of family-centred care. RESULTS: Our search identified 2882 citations, from which 63 articles describing 61 unique interventions met the eligibility criteria and were included in this review. The most common study designs were quasiexperimental studies (n = 18), randomized controlled trials (n = 11) and qualitative and mixed-methods studies (n = 9 each). The most frequently addressed domains of family-centred care were communication and information provision (n = 45), family involvement in care (n = 37) and access to care (n = 30). CONCLUSION: This review, which identified 61 unique interventions aimed at improving family-centred care for children with chronic conditions across a range of settings, is a concrete resource for researchers, health care providers and administrators interested in improving care for this high-needs population. PATIENT OR PUBLIC CONTRIBUTION: This study was co-developed with three patient partner co-investigators, all of whom are individuals with lived experiences of rare chronic diseases as parents and/or patients and have prior experience in patient engagement in research (I. J., N. P., M. S.). These patient partner co-investigators contributed to this study at all stages, from conceptualization to dissemination.

Assessing the quality and value of metabolic chart data for capturing core outcomes for pediatric medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.

BACKGROUND: Generating rigorous evidence to inform care for rare diseases requires reliable, sustainable, and longitudinal measurement of priority outcomes. Having developed a core outcome set for pediatric medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, we aimed to assess the feasibility of prospective measurement of these core outcomes during routine metabolic clinic visits. METHODS: We used existing cohort data abstracted from charts of 124 children diagnosed with MCAD deficiency who participated in a Canadian study which collected data from birth to a maximum of 11 years of age to investigate the frequency of clinic visits and quality of metabolic chart data for selected outcomes. We recorded all opportunities to collect outcomes from the medical chart as a function of visit rate to the metabolic clinic, by treatment centre and by child age. We applied a data quality framework to evaluate data based on completeness, conformance, and plausibility for four core MCAD outcomes: emergency department use, fasting time, metabolic decompensation, and death. RESULTS: The frequency of metabolic clinic visits decreased with increasing age, from a rate of 2.8 visits per child per year (95% confidence interval, 2.3-3.3) among infants 2 to 6 months, to 1.0 visit per child per year (95% confidence interval, 0.9-1.2) among those ≥ 5 years of age. Rates of emergency department visits followed anticipated trends by child age. Supplemental findings suggested that some emergency visits occur outside of the metabolic care treatment centre but are not captured. Recommended fasting times were updated relatively infrequently in patients' metabolic charts. Episodes of metabolic decompensation were identifiable but required an operational definition based on acute manifestations most commonly recorded in the metabolic chart. Deaths occurred rarely in these patients and quality of mortality data was not evaluated. CONCLUSIONS: Opportunities to record core outcomes at the metabolic clinic occur at least annually for children with MCAD deficiency. Methods to comprehensively capture emergency care received at outside institutions are needed. To reduce substantial heterogeneous recording of core outcome across treatment centres, improved documentation standards are required for recording of recommended fasting times and a consensus definition for metabolic decompensations needs to be developed and implemented.

Expanding the phenotypic and molecular spectrum of NFS1-related disorders that cause functional deficiencies in mitochondrial and cytosolic iron-sulfur cluster containing enzymes.

Iron-sulfur cluster proteins are involved in critical functions for gene expression regulation and mitochondrial bioenergetics including the oxidative phosphorylation system. The c.215G>A p.(Arg72Gln) variant in NFS1 has been previously reported to cause infantile mitochondrial complex II and III deficiency. We describe three additional unrelated patients with the same missense variant. Two infants with the same homozygous variant presented with hypotonia, weakness and lactic acidosis, and one patient with compound heterozygous p.(Arg72Gln) and p.(Arg412His) variants presented as a young adult with gastrointestinal symptoms and fatigue. Skeletal muscle biopsy from patients 1 and 3 showed abnormal mitochondrial morphology, and functional analyses demonstrated decreased activity in respiratory chain complex II and variably in complexes I and III. We found decreased mitochondrial and cytosolic aconitase activities but only mildly affected lipoylation of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase enzymes. Our studies expand the phenotypic spectrum and provide further evidence for the pathogenicity and functional sequelae of NFS1-related disorders with disturbances in both mitochondrial and cytosolic iron-sulfur cluster containing enzymes.

Diagnostic Utility of Genome-wide DNA Methylation Testing in Genetically Unsolved Individuals with Suspected Hereditary Conditions.

Conventional genetic testing of individuals with neurodevelopmental presentations and congenital anomalies (ND/CAs), i.e., the analysis of sequence and copy number variants, leaves a substantial proportion of them unexplained. Some of these cases have been shown to result from DNA methylation defects at a single locus (epi-variants), while others can exhibit syndrome-specific DNA methylation changes across multiple loci (epi-signatures). Here, we investigate the clinical diagnostic utility of genome-wide DNA methylation analysis of peripheral blood in unresolved ND/CAs. We generate a computational model enabling concurrent detection of 14 syndromes using DNA methylation data with full accuracy. We demonstrate the ability of this model in resolving 67 individuals with uncertain clinical diagnoses, some of whom had variants of unknown clinical significance (VUS) in the related genes. We show that the provisional diagnoses can be ruled out in many of the case subjects, some of whom are shown by our model to have other diseases initially not considered. By applying this model to a cohort of 965 ND/CA-affected subjects without a previous diagnostic assumption and a separate assessment of rare epi-variants in this cohort, we identify 15 case subjects with syndromic Mendelian disorders, 12 case subjects with imprinting and trinucleotide repeat expansion disorders, as well as 106 case subjects with rare epi-variants, a portion of which involved genes clinically or functionally linked to the subjects' phenotypes. This study demonstrates that genomic DNA methylation analysis can facilitate the molecular diagnosis of unresolved clinical cases and highlights the potential value of epigenomic testing in the routine clinical assessment of ND/CAs.

Clinical and technical assessment of MedExome vs. NGS panels in patients with suspected genetic disorders in Southwestern Ontario.

The adaptation of a broad genomic sequencing approach in the clinical setting has been accompanied by considerations regarding the clinical utility, technical performance, and diagnostic yield compared to targeted genetic approaches. We have developed MedExome, an integrated framework for sequencing, variant calling (SNVs, Indels, and CNVs), and clinical assessment of ~4600 medically relevant genes. We compared the technical performance of MedExome with the whole-exome and targeted gene-panel sequencing, assessed the reasons for discordance, and evaluated the added clinical yield of MedExome in a cohort of unresolved subjects suspected of genetic disease. Our analysis showed that despite a higher average read depth in panels (3058 vs. 855), MedExome yielded full coverage of the enriched regions (>20X) and 99% variant concordance rate with panels. The discordance rate was associated with low-complexity regions, high-GC content, and low allele fractions, observed in both platforms. MedExome yielded full sensitivity in detecting clinically actionable variants, and the assessment of 138 patients with suspected genetic conditions resulted in 76 clinical reports (31 full [22.1%], 3 partial, and 42 uncertain/possible molecular diagnoses). MedExome sequencing has comparable performance in variant detection to gene panels. Added diagnostic yield justifies expanded implementation of broad genomic approaches in unresolved patients; however, cost-benefit and health systems impact warrants assessment.

The phenotypic spectrum of AMER1-related osteopathia striata with cranial sclerosis: The first Canadian cohort.

Osteopathia striata with cranial sclerosis (OSCS; OMIM# 300373) is a rare X-linked disorder caused by mutations of the AMER1 gene. OSCS is traditionally considered a skeletal dysplasia, characterized by cranial sclerosis and longitudinal striations in the long bone metaphyses. However, OSCS affects many body systems and varies significantly in phenotypic severity between individuals. This case series focuses on the phenotypic presentation and development of individuals with OSCS. We provide an account of 12 patients with OSCS, ranging from 5 months to 38 years of age. These patients were diagnosed with OSCS after genetic testing confirmed pathogenic mutations in AMER1. Patient consent was obtained for photos and participation. Data were collected regarding perinatal history, dysmorphic features, and review of systems. This case series documents common facial dysmorphology, as well as rare extraskeletal features of OSCS, including two patients with intestinal malrotation and two patients with pyloric stenosis. We share four apparently nonmosaic males with OSCS (one de novo and three maternal variants). We also provide a clinical update on a patient who was previously published by Chénier et al. (2012). American Journal of Medical Genetics Part A, 158, 2946-2952. More research is needed to investigate the links between genotype and phenotype and assess the long-term comorbidities and overall quality of life of individuals with OSCS.

The expanding clinical phenotype of germline ABL1-associated congenital heart defects and skeletal malformations syndrome.

Congenital heart defects and skeletal malformations syndrome (CHDSKM) is a rare autosomal dominant disorder characterized by congenital heart disease, skeletal abnormalities, and failure to thrive. CHDSKM is caused by germline mutations in ABL1. To date, three variants have been in association with CHDSKM. In this study, we describe three de novo missense variants, c.407C>T (p.Thr136Met), c.746C>T (p.Pro249Leu), and c.1573G>A (p.Val525Met), and one recurrent variant, c.1066G>A (p.Ala356Thr), in six patients, thereby expanding the phenotypic spectrum of CHDSKM to include hearing impairment, lipodystrophy-like features, renal hypoplasia, and distinct ocular abnormalities. Functional investigation of the three novel variants showed an increased ABL1 kinase activity. The cardiac findings in additional patients with p.Ala356Thr contribute to the accumulating evidence that patients carrying either one of the recurrent variants, p.Tyr245Cys and p.Ala356Thr, have a high incidence of cardiac abnormalities. The phenotypic expansion has implications for the clinical diagnosis of CHDSKM in patients with germline ABL1 variants.

Heterozygous De Novo UBTF Gain-of-Function Variant Is Associated with Neurodegeneration in Childhood.

Ribosomal RNA (rRNA) is transcribed from rDNA by RNA polymerase I (Pol I) to produce the 45S precursor of the 28S, 5.8S, and 18S rRNA components of the ribosome. Two transcription factors have been defined for Pol I in mammals, the selectivity factor SL1, and the upstream binding transcription factor (UBF), which interacts with the upstream control element to facilitate the assembly of the transcription initiation complex including SL1 and Pol I. In seven unrelated affected individuals, all suffering from developmental regression starting at 2.5-7 years, we identified a heterozygous variant, c.628G>A in UBTF, encoding p.Glu210Lys in UBF, which occurred de novo in all cases. While the levels of UBF, Ser388 phosphorylated UBF, and other Pol I-related components (POLR1E, TAF1A, and TAF1C) remained unchanged in cells of an affected individual, the variant conferred gain of function to UBF, manifesting by markedly increased UBF binding to the rDNA promoter and to the 5'- external transcribed spacer. This was associated with significantly increased 18S expression, and enlarged nucleoli which were reduced in number per cell. The data link neurodegeneration in childhood with altered rDNA chromatin status and rRNA metabolism.

Further delineation of Basel-Vanagaite-Smirin-Yosef syndrome: Report of three patients.

Basel-Vanagaite-Smirin-Yosef syndrome is a recently described autosomal recessive intellectual disability syndrome caused by variants in the MED25 gene. While it was originally identified in Brazil, it was further described in Israel by authors who are now the namesake of the condition. A 2018 publication further contributed to its delineation, but the patient's phenotype was complicated by a dual diagnosis. More recently, an article describing a set of affected siblings was published. We describe three, previously unreported, patients showing clinical variability for this newly defined syndrome. The major features determined by "reverse phenotyping" include significant to profound developmental delays/intellectual disability with absent or delayed speech, epilepsy, ocular abnormalities, cleft lip and/or palate, congenital heart disease, urogenital anomalies, skeletal abnormalities, brain malformations and/or microcephaly, failure to thrive, and dysmorphic features. The authors suggest the delineation of an acronym using the gene name and common features seen across the majority of patients reported so far. This new nomination, MED-DOCS, may help clinicians to recognize, suspect, and remember this novel syndrome.

Growth hormone deficiency in megalencephaly-capillary malformation syndrome: An association with activating mutations in PIK3CA.

Megalencephaly-capillary malformation syndrome (MCAP) is a brain overgrowth disorder characterized by cortical malformations (specifically polymicrogyria), vascular anomalies, and segmental overgrowth secondary to somatic activating mutations in the PI3K-AKT-MTOR pathway (PIK3CA). Cases of growth failure and hypoglycemia have been reported in patients with MCAP, raising the suspicion for unappreciated growth hormone (GH) deficiency. Here we report an observational multicenter study of children with MCAP and GH deficiency. Eleven participants were confirmed to have GH deficiency, all with very low or undetectable circulating concentrations of insulin-like growth factor-1 and insulin-like growth factor binding protein-3. Seven underwent GH stimulation testing and all had insufficient responses with a median GH peak of 3.7 ng/ml (range 1.1-8.6). Growth patterns revealed a drastic decline in length z-scores within the first year of life but then stabilized afterward. Five were treated with GH; one discontinued due to inconsolability. The other four participants continued on GH with improvement in linear growth velocity. Other endocrinopathies were identified in 7 of the 11 participants in this cohort. This study indicates that GH deficiency is associated with MCAP and that children with MCAP and hypoglycemia and/or postnatal growth failure should be evaluated for GH deficiency and other endocrinopathies.

Cohesin complex-associated holoprosencephaly.

Marked by incomplete division of the embryonic forebrain, holoprosencephaly is one of the most common human developmental disorders. Despite decades of phenotype-driven research, 80-90% of aneuploidy-negative holoprosencephaly individuals with a probable genetic aetiology do not have a genetic diagnosis. Here we report holoprosencephaly associated with variants in the two X-linked cohesin complex genes, STAG2 and SMC1A, with loss-of-function variants in 10 individuals and a missense variant in one. Additionally, we report four individuals with variants in the cohesin complex genes that are not X-linked, SMC3 and RAD21. Using whole mount in situ hybridization, we show that STAG2 and SMC1A are expressed in the prosencephalic neural folds during primary neurulation in the mouse, consistent with forebrain morphogenesis and holoprosencephaly pathogenesis. Finally, we found that shRNA knockdown of STAG2 and SMC1A causes aberrant expression of HPE-associated genes ZIC2, GLI2, SMAD3 and FGFR1 in human neural stem cells. These findings show the cohesin complex as an important regulator of median forebrain development and X-linked inheritance patterns in holoprosencephaly.

Kidney disease and organ transplantation in methylmalonic acidaemia.

OBJECTIVES: MMA is associated with chronic tubulointerstitial nephritis and a progressive decline in GFR. Optimal management of these children is uncertain. Our objectives were to document the pre-, peri-, and post-transplant course of all children with MMA who underwent liver or combined liver-kidney transplant in our centers. DESIGN AND METHODS: Retrospective chart review of all cases of MMA who underwent organ transplantation over the last 10 years. RESULTS: Five children with MMA underwent liver transplant (4/5) and combined liver-kidney transplant (1/5). Three were Mut0 and two had a cobalamin B disorder. Four of five were transplanted between ages 3 and 5 years. Renal dysfunction prior to transplant was seen in 2/5 patients. Post-transplant (one liver transplant and one combined transplant) renal function improved slightly when using creatinine-based GFR formula. We noticed in 2 patients a big discrepancy between creatinine- and cystatin C-based GFR calculations. One patient with no renal disease developed renal failure post-liver transplantation. Serum MMA levels have decreased in all to <300 µmol/L. Four patients remain on low protein diet, carnitine, coenzyme Q, and vitamin E post-transplant. CONCLUSIONS: MMA is a complex metabolic disorder. Renal disease can continue to progress post-liver transplant and close follow-up is warranted. More research is needed to clarify best screening GFR method in patients with MMA. Whether liver transplant alone, continued protein restriction, or the addition of antioxidants post-transplant can halt the progression of renal disease remains unclear.

Infantile-Onset Multisystem Neurologic, Endocrine, and Pancreatic Disease: Case and Review.

We report three brothers born to consanguineous parents of Syrian descent, with a homozygous novel c.324G>A (p.W108*) mutation in PTRH2 that encodes peptidyl-tRNA hydrolase 2, causing infantile-onset multisystem neurologic, endocrine, and pancreatic disease (IMNEPD). We describe the core clinical features of postnatal microcephaly, motor and language delay with regression, ataxia, and hearing loss. Additional features include epileptic seizures, pancreatic insufficiency, and peripheral neuropathy. Clinical phenotyping enabled a targeted approach to the investigation and identification of a novel homozygous nonsense mutation in PTRH2, c.324G>A (p.W108*). We compare our patients with those recently described and review the current literature for IMNEPD.

Compte-rendu d'un cas de maladie infantile multi-systémique neurologique-endocrinienne-pancréatique. Nous voulons nous pencher ici sur le cas de trois frères nés de parents consanguins d'origine syrienne et donnant à voir une mutation homozygote c.324G>A (p.W108*) du gène PTRH2 rarement vue. Ce gène est responsable d'encoder la protéine peptidyl-tRNA hydrolase 2. Un encodage déficient causera chez des enfants une maladie multi-systémique neurologique-endocrinienne-pancréatique. Dans cet article, nous entendons décrire les aspects cliniques principaux de la microcéphalie postnatale, à savoir des délais et des régressions sur le plan du développement moteur et langagier mais aussi de l'ataxie et de la perte auditive. D'autres aspects cliniques sont également abordés, notamment des crises épileptiques, l'insuffisance pancréatique et une neuropathie périphérique. À cet égard, des outils de phénotypage clinique nous ont permis de compter sur une approche de recherche et d'identification ciblée en ce qui regarde la mutation non-sens évoquée ci-dessus. Enfin, nous voulons comparer nos jeunes patients à d'autres récemment décrits et passer en revue la littérature scientifique actuelle qui porte sur la maladie infantile multi-systémique neurologique-endocrinienne-pancréatique.

CODAS syndrome is associated with mutations of LONP1, encoding mitochondrial AAA+ Lon protease.

CODAS syndrome is a multi-system developmental disorder characterized by cerebral, ocular, dental, auricular, and skeletal anomalies. Using whole-exome and Sanger sequencing, we identified four LONP1 mutations inherited as homozygous or compound-heterozygous combinations among ten individuals with CODAS syndrome. The individuals come from three different ancestral backgrounds (Amish-Swiss from United States, n = 8; Mennonite-German from Canada, n = 1; mixed European from Canada, n = 1). LONP1 encodes Lon protease, a homohexameric enzyme that mediates protein quality control, respiratory-complex assembly, gene expression, and stress responses in mitochondria. All four pathogenic amino acid substitutions cluster within the AAA(+) domain at residues near the ATP-binding pocket. In biochemical assays, pathogenic Lon proteins show substrate-specific defects in ATP-dependent proteolysis. When expressed recombinantly in cells, all altered Lon proteins localize to mitochondria. The Old Order Amish Lon variant (LONP1 c.2161C>G[p.Arg721Gly]) homo-oligomerizes poorly in vitro. Lymphoblastoid cell lines generated from affected children have (1) swollen mitochondria with electron-dense inclusions and abnormal inner-membrane morphology; (2) aggregated MT-CO2, the mtDNA-encoded subunit II of cytochrome c oxidase; and (3) reduced spare respiratory capacity, leading to impaired mitochondrial proteostasis and function. CODAS syndrome is a distinct, autosomal-recessive, developmental disorder associated with dysfunction of the mitochondrial Lon protease.

Nephrological and urological complications of homozygous c.974G>A (p.Arg325Gln) OSGEP mutations.

BACKGROUND: Galloway-Mowat syndrome (GAMOS) (OMIM #251300) is a severe autosomal recessive disease characterized by the combination of early-onset steroid-resistant nephrotic syndrome (SRNS) and microcephaly with brain anomalies caused by WDR73 as well as OSGEP, TP53RK, TPRKB, or LAGE3 mutations. OBJECTIVE: We report on the hitherto undescribed urological and nephrological complications of the homozygous c.974G>A (p.Arg325Gln) OSGEP mutations in a 7-year-old Caucasian girl. CASE DIAGNOSIS: The patient came to the attention of pediatric nephrology at the age of 3 years and 11 months, when she presented with status epilepticus due to profound hypomagnesemia (0.31 mmol/L, normal 0.65-1.05). A 24-h urine demonstrated a magnesium loss of 0.6 mmol/kg/day with associated proteinuria suggesting renal tubulopathy. Subsequently, she developed recurrent urinary tract infections (UTIs) and was diagnosed with neurogenic bladder dysfunction. The patient continued to have UTIs associated with seizures and sequential cultures growing multi-drug-resistant organisms despite of antibiotic prophylaxis. In addition, the proteinuria (median microalbumin/creatinine ratio 647 mg/mmol) increased, and she developed partial Fanconi syndrome. At age 7, she developed a large bladder calculus (3.3 × 3.2 cm) and three left non-obstructing renal calculi associated with elevated urinary cystine, hypercalciuria, and ongoing hypomagnesemia and required surgical intervention. Glomerular filtration rate (GFR) remained normal and she never developed frank nephrotic syndrome (average albumin 31 g/L). CONCLUSIONS: It is unclear if patients with OSGEP mutations with tubular symptoms rather than nephrotic syndrome should be considered a different entity. Nephrological and urological complications of OSGEP mutations can be challenging and require a multidisciplinary approach.