De Novo Variants in LMNB1 Cause Pronounced Syndromic Microcephaly and Disruption of Nuclear Envelope Integrity.

Lamin B1 plays an important role in the nuclear envelope stability, the regulation of gene expression, and neural development. Duplication of LMNB1, or missense mutations increasing LMNB1 expression, are associated with autosomal-dominant leukodystrophy. On the basis of its role in neurogenesis, it has been postulated that LMNB1 variants could cause microcephaly. Here, we confirm this hypothesis with the identification of de novo mutations in LMNB1 in seven individuals with pronounced primary microcephaly (ranging from -3.6 to -12 SD) associated with relative short stature and variable degree of intellectual disability and neurological features as the core symptoms. Simplified gyral pattern of the cortex and abnormal corpus callosum were noted on MRI of three individuals, and these individuals also presented with a more severe phenotype. Functional analysis of the three missense mutations showed impaired formation of the LMNB1 nuclear lamina. The two variants located within the head group of LMNB1 result in a decrease in the nuclear localization of the protein and an increase in misshapen nuclei. We further demonstrate that another mutation, located in the coil region, leads to increased frequency of condensed nuclei and lower steady-state levels of lamin B1 in proband lymphoblasts. Our findings collectively indicate that de novo mutations in LMNB1 result in a dominant and damaging effect on nuclear envelope formation that correlates with microcephaly in humans. This adds LMNB1 to the growing list of genes implicated in severe autosomal-dominant microcephaly and broadens the phenotypic spectrum of the laminopathies.

Sleep disturbances in Phelan-McDermid syndrome: Clinical and metabolic profiling of 56 individuals.

Phelan-McDermid Syndrome (PMS) is caused by deletions at chromosome 22q13.3 or pathogenic/likely pathogenic SHANK3 variants. The clinical presentation is extremely variable and includes global developmental delay/intellectual disability (ID), seizures, neonatal hypotonia, and sleep disturbances, among others. This study investigated the prevalence of sleep disturbances, and the genetic and metabolic features associated with them, in a cohort of 56 individuals with PMS. Sleep data were collected via standardized observer/caregiver questionnaires, while genetic data from array-CGH and sequencing of 9 candidate genes within the 22q13.3 region, and metabolic profiling utilized the Biolog Phenotype Mammalian MicroArray plates. Sleep disturbances were present in 64.3% of individuals with PMS, with the most common problem being waking during the night (39%). Sleep disturbances were more prevalent in individuals with a SHANK3 pathogenic variant (89%) compared to subjects with 22q13.3 deletions of any size (59.6%). Distinct metabolic profiles for individuals with PMS with and without sleep disturbances were also identified. These data are helpful information for recognizing and managing sleep disturbances in individuals with PMS, outlining the main candidate gene for this neurological manifestation, and highlighting potential biomarkers for early identification of at-risk subjects and molecular targets for novel treatment approaches.

Epidemiology of Tumor-Induced Osteomalacia in Germany Based on Real World Data.

Tumor-induced osteomalacia (TIO) is an ultra-rare disease caused mostly by benign tumors that secrete fibroblast growth factor-23. Because of nonspecific symptoms, the diagnostic delay is long, and therapy can be challenging. Moreover, epidemiological data on TIO are scarce owing to its rarity. Therefore, this study aimed to quantify TIO's incidence rates and prevalence in Germany. Retrospective longitudinal and cross-sectional analyses were conducted using anonymized German claims data from the statutory health insurance (SHI) database. This database, which comprises the data of approximately 5 million insurants, is a representative sample of the German population and supports national projections. As there is no unique International Statistical Classification of Diseases and Related Health Problems (ICD) code for TIO, operational categories based on different surrogates were defined to determine the prevalence and incidence rates of TIO among probable patients. This study showed that TIO has a prevalence of (documented code, advanced imaging, medication, or tumor removal) 0.187 per 100,000 persons and an incidence rate of ≤ 0.094 per 100,000 person years. This analysis provides the first epidemiological insight into German patients with TIO. Despite the general limitations associated with the analysis of SHI claims data of ultra-rare diseases, we believe that this analysis provides a sound basis for further analysis, particularly with regard to the care situation of patients with TIO.

Epidemiology of mature T/NK-cell lymphomas in Germany - A representative cross-sectional study based on SHI claims data.

BACKGROUND: Primary cutaneous lymphomas (PCL) are rare skin tumors of lymphoproliferative neoplasms and belong to the heterogeneous group of non-Hodgkin's lymphomas. PCL encompass a broad spectrum of clinical and histologic manifestations, with cutaneous T-cell lymphoma (CTCL) being the most common (73%). Due to the rarity of the diseases, population-based studies of care and epidemiology are limited. PATIENTS AND METHODS: Based on anonymized, age- and sex-adjusted SHI (statutory health insurance) claims data of approximately five million SHI-insured patients, a retrospective analysis was conducted over a six-year period (2012-2017) to determine the prevalence, incidence, and lethality in patients with mature-cell T/NK-cell lymphoma in Germany. RESULTS: A total of 1,336 patients with T-cell lymphoma were identified during the observation period. The six-year prevalence ranged from 27.35 to 43.58 per 100,000. Patients were 65% male with a mean age of 66 years (SD 15). There were 246 patients (approx. 20%) who died within the 6 years, up to 7% per year. The calculated incidence in 153 identified patients in 2017 is 3.65 to 3.92 per 100,000. CONCLUSIONS: For the first time, valid epidemiologic findings of patients with mature T-cell and NK-cell lymphomas were obtained using SHI claims data in Germany. Further analyses are needed to gain a deeper insight into the healthcare reality of patients with this rare disease.

Genetic and metabolic profiling of individuals with Phelan-McDermid syndrome presenting with seizures.

Phelan-McDermid syndrome (PMS) (OMIM*606232) is a rare genetic disorder characterized by intellectual disability, autistic features, speech delay, minor dysmorphia, and seizures. This study was conducted to investigate the prevalence of seizures and the association with genetic and metabolic features since there has been little research related to seizures in PMS. For 57 individuals, seizure data was collected from caregiver interviews, genetic data from existing cytogenetic records and Sanger sequencing for nine 22q13 genes, and metabolic profiling from the Phenotype Mammalian MicroArray (PM-M) developed by Biolog. Results showed that 46% of individuals had seizures with the most common type being absence and grand-mal seizures. Seizures were most prevalent in individuals with pathogenic SHANK3 mutations (70%), those with deletion sizes >4 Mb (16%), and those with deletion sizes <4 Mb (71%) suggesting involvement of genes in addition to SHANK3. Additionally, a 3 Mb genomic region on 22q13.31 containing the gene TBC1D22A, was found to be significantly associated with seizure prevalence. A distinct metabolic profile was identified for individuals with PMS with seizures and suggested among other features a disrupted utilization of main energy sources using Biolog plates. The results of this study will be helpful for clinicians and families in anticipating seizures in these children and for researchers to identify candidate genes for the seizure phenotype.

Care reality of menopausal women in Germany: healthcare research using quantitative (SHI claims data) and qualitative (survey) data collection.

PURPOSE: The transition from the fertile phase of life to menopause is associated with numerous physical changes. Hormone replacement therapy (HRT), as the most effective and efficient form of drug treatment, involves the use of oestrogens and progestins with the aim of increasing health-related quality of life through symptom reduction, sleep improvement and affect enhancement. METHODS: The medical care situation and disease burden of menopausal women was investigated by means of a survey of 1000 women aged 45-60 years on the topics of quality of life, menopause and HRT and a quantitative, longitudinal healthcare study based on an anonymised and age- and sex-adjusted Statutory Health Insurance (SHI) routine data set with approximately four million anonymous insured persons per year. RESULTS: Out of more than half a million women aged 35-70 years, and with statutory health insurance, (n = 613,104), 14% (n = 82,785) had climacteric disorder documented as a first diagnosis in 2014. The proportion of women with the climacteric disorder, who were prescribed HRT on an outpatient basis, was 21%; according to the forsa survey, 50% of the women surveyed felt moderate to poorly/very poorly informed about treatment options. CONCLUSION: Findings from the health insurance research conducted with different data sources (survey and SHI claims data) indicate the need for increasing awareness and providing an early and informative education on HRT and its risks and benefits.

Real-world data and treatment patterns of patients with lower urinary tract symptoms due to benign prostatic hyperplasia in Germany: an observational study using health insurance claims data.

PURPOSE: Benign prostatic hyperplasia (BPH) is associated with lower urinary tract symptoms (LUTS), representing one of the most common urological conditions. However, insights into the actual healthcare of this patient cohort in Germany are scarce. We aimed to retrospectively analyse management patterns of patients with LUTS in Germany using health insurance claims databases. METHODS: A retrospective, longitudinal cohort analysis was conducted obtaining claims data from the German InGef health insurance database containing approximately five million member-records from over 60 nationwide statutory health insurances. First, a cross-sectional prevalence analysis was performed on all individuals with a diagnosis on LUTS (ICD-10 GM N40) in 2018. Second, a longitudinal analysis of individuals with either a newly started BPH medication or initial BPH surgery who were indexed in 2014 and followed-up for 4 years. RESULTS: In 2018, 132,386 (6.7%) prevalent BPH patients were identified from 1,979,916 continuously insured males. A potential overcoding bias could not be assessed which may influence the outpatient sector estimation. 10,361 (0.7%) patients were identified with incident BPH medication and 1768 (0.1%) patients with incident BPH surgery out of 1,575,604 males (2013-2018). Alpha-blockers were the drug of choice (95.6%) in the first year. Half of patients received specific BPH medications four years after index, while almost 98% of initial BPH surgeries were performed within the inpatient setting. TURP was the most frequent surgical intervention (76%). CONCLUSIONS: A widespread diffusion of alternative individualized minimally invasive approaches in the outpatient sector might address pharmacotherapy discontinuation and patient-access barriers to other treatments.

Imaging Intensity and Survival Outcomes in High-Risk Resected Melanoma Treated by Systemic Therapy at Recurrence.

BACKGROUND: Intensive imaging in melanoma remains controversial because its survival impact is unknown. We investigated the impact of imaging intensity on the rates of asymptomatic surveillance-detected recurrence (ASDR) and subsequent treatment outcomes in patients with access to immune checkpoint inhibitors (ICIs) and targeted therapy (TT). METHODS: Patients with resected malignant melanoma undergoing imaging surveillance at a single center between 2006 and 2016 were identified. Surveillance and recurrence characteristics (imaging, symptom, treatment, and survival data) were retrospectively collected. Univariate (t test, Chi square test) and multivariate Cox regression analyses were conducted. RESULTS: Of 353 high-risk melanoma patients (stage IIB, 24%; IIC, 19%; IIIA, 27%; IIIB, 16%; IIIC, 14%), 71 (45%) had ASDR and 88 (55%) had symptomatic recurrence (SR). Shorter imaging intervals identified more ASDR (57%, 0-6 months; 34%, 6-12 months; 33%, > 12 months; p = 0.03). ASDR had better prognostic factors than SR [fewer than three metastatic sites (43 vs. 21%, p = 0.003), normal lactate dehydrogenase (LDH; 53 vs. 38%, p = 0.09), brain metastases (11 vs. 40%, p < 0.001)] and received more systemic treatment (72 vs. 49%, p = 0.003; ICIs 55 vs. 31%, p = 0.002; TT 8 vs. 13%, p = 0.41). ASDR had better survival outcomes on ICI treatment (2-year OS, 56 vs. 31%, p < 0.001). Median OS from surveillance start was 39.6 vs. 22.8 months (p < 0.001). ASDR was independently associated with survival (hazard ratio 0.47, 95% confidence interval 0.29-0.78, p = 0.003), adjusting for stage, sex, age, disease burden, LDH, era of recurrence, brain metastases, and ICI/TT treatment. CONCLUSIONS: These real-world data support further study on intensified imaging surveillance protocols for high-risk resected melanoma, as ASDR was associated with superior survival outcomes from ICI therapy.

Correction to: Imaging Intensity and Survival Outcomes in High-Risk Resected Melanoma Treated by Systemic Therapy at Recurrence.

In the original article, the survival curves are missing in Fig. 1c, d.

MED12-related XLID disorders are dose-dependent of immediate early genes (IEGs) expression.

Mediator occupies a key role in protein coding genes expression in mediating the contacts between gene specific factors and the basal transcription machinery but little is known regarding the role of each Mediator subunits. Mutations in MED12 are linked with a broad spectrum of genetic disorders with X-linked intellectual disability that are difficult to range as Lujan, Opitz-Kaveggia or Ohdo syndromes. Here, we investigated several MED12 patients mutations (p.R206Q, p.N898D, p.R961W, p.N1007S, p.R1148H, p.S1165P and p.R1295H) and show that each MED12 mutations cause specific expression patterns of JUN, FOS and EGR1 immediate early genes (IEGs), reflected by the presence or absence of MED12 containing complex at their respective promoters. Moreover, the effect of MED12 mutations has cell-type specificity on IEG expression. As a consequence, the expression of late responsive genes such as the matrix metalloproteinase-3 and the RE1 silencing transcription factor implicated respectively in neural plasticity and the specific expression of neuronal genes is disturbed as documented for MED12/p.R1295H mutation. In such case, JUN and FOS failed to be properly recruited at their AP1-binding site. Our results suggest that the differences between MED12-related phenotypes are essentially the result of distinct IEGs expression patterns, the later ones depending on the accurate formation of the transcription initiation complex. This might challenge clinicians to rethink the traditional syndromes boundaries and to include genetic criterion in patients' diagnostic.

Outcome comparison of integrated psycho-oncological care versus unstructured care-Results of a non-randomised open-label two-arm trial.

OBJECTIVE: To compare patients' experiences with a systematic, integrated psycho-oncological care (IC) model to experiences with "care as usual" (CAU). METHODS: To improve patients' knowledge about psychosocial support options and to facilitate use, an IC model was developed by psycho-oncologists and a health insurance company and implemented in one German cancer care facility. Using a parallel, non-randomised design, these patients' experiences were compared to CAU patients. In 2015, both patient groups received questionnaires 6-12 months post-inpatient treatment. Main outcomes were awareness, use and opinion of psycho-oncological care (PC) and anxiety level (Generalized Anxiety Disorder Scale (GAD-7)). RESULTS: 228 patients (IC = 90; CAU = 138) participated (response rate 24%). More IC patients felt adequately informed about PC (63% vs. 46%, ORadj : 2.5 (CI: 1.3-4.8); p = 0.008). More IC patients recalled being offered various support options and had had at least one PC discussion (44% vs. 33%, ORadj of IC patient saying "yes" instead of "No, didn't want to" compared to a CAU patient: 0.4 (CI: 0.2-0.8); p = 0.01). More IC patients rated their care as good/excellent (49% vs. 38%, ORadj : 1.8 (CI: 0.7-4.1; p = 0.2)). Anxiety levels were similar (GAD-7 score>=10: IC 34% vs. CAU 28%; p = 0.4). CONCLUSION: Structured psycho-oncological care had some positive results on the outcomes, but anxiety levels did not differ.

Identification and characterization of a missense mutation in the O-linked ß-N-acetylglucosamine (O-GlcNAc) transferase gene that segregates with X-linked intellectual disability.

O-GlcNAc is a regulatory post-translational modification of nucleocytoplasmic proteins that has been implicated in multiple biological processes, including transcription. In humans, single genes encode enzymes for its attachment (O-GlcNAc transferase (OGT)) and removal (O-GlcNAcase (OGA)). An X-chromosome exome screen identified a missense mutation, which encodes an amino acid in the tetratricopeptide repeat, in OGT (759G>T (p.L254F)) that segregates with X-linked intellectual disability (XLID) in an affected family. A decrease in steady-state OGT protein levels was observed in isolated lymphoblastoid cell lines from affected individuals, consistent with molecular modeling experiments. Recombinant expression of L254F-OGT demonstrated that the enzyme is active as both a glycosyltransferase and an HCF-1 protease. Despite the reduction in OGT levels seen in the L254F-OGT individual cells, we observed that steady-state global O-GlcNAc levels remained grossly unaltered. Surprisingly, lymphoblastoids from affected individuals displayed a marked decrease in steady-state OGA protein and mRNA levels. We observed an enrichment of the OGT-containing transcriptional repressor complex mSin3A-HDAC1 at the proximal promoter region of OGA and correspondingly decreased OGA promoter activity in affected cells. Global transcriptome analysis of L254F-OGT lymphoblastoids compared with controls revealed a small subset of genes that are differentially expressed. Thus, we have begun to unravel the molecular consequences of the 759G>T (p.L254F) mutation in OGT that uncovered a compensation mechanism, albeit imperfect, given the phenotype of affected individuals, to maintain steady-state O-GlcNAc levels. Thus, a single amino acid substitution in the regulatory domain (the tetratricopeptide repeat domain) of OGT, which catalyzes the O-GlcNAc post-translational modification of nuclear and cytosolic proteins, appears causal for XLID.

ZC4H2, an XLID gene, is required for the generation of a specific subset of CNS interneurons.

Miles-Carpenter syndrome (MCS) was described in 1991 as an XLID syndrome with fingertip arches and contractures and mapped to proximal Xq. Patients had microcephaly, short stature, mild spasticity, thoracic scoliosis, hyperextendable MCP joints, rocker-bottom feet, hyperextended elbows and knees. A mutation, p.L66H, in ZC4H2, was identified in a XLID re-sequencing project. Additional screening of linked families and next generation sequencing of XLID families identified three ZC4H2 mutations: p.R18K, p.R213W and p.V75in15aa. The families shared some relevant clinical features. In silico modeling of the mutant proteins indicated all alterations would destabilize the protein. Knockout mutations in zc4h2 were created in zebrafish and homozygous mutant larvae exhibited abnormal swimming, increased twitching, defective eye movement and pectoral fin contractures. Because several of the behavioral defects were consistent with hyperactivity, we examined the underlying neuronal defects and found that sensory neurons and motoneurons appeared normal. However, we observed a striking reduction in GABAergic interneurons. Analysis of cell-type-specific markers showed a specific loss of V2 interneurons in the brain and spinal cord, likely arising from mis-specification of neural progenitors. Injected human wt ZC4H2 rescued the mutant phenotype. Mutant zebrafish injected with human p.L66H or p.R213W mRNA failed to be rescued, while the p.R18K mRNA was able to rescue the interneuron defect. Our findings clearly support ZC4H2 as a novel XLID gene with a required function in interneuron development. Loss of function of ZC4H2 thus likely results in altered connectivity of many brain and spinal circuits.

A recurrent mutation in MED12 leading to R961W causes Opitz-Kaveggia syndrome.

Opitz-Kaveggia syndrome (also known as FG syndrome) is an X-linked disorder characterized by mental retardation, relative macrocephaly, hypotonia and constipation. We report here that the original family for whom the condition is named and five other families have a recurrent mutation (2881C>T, leading to R961W) in MED12 (also called TRAP230 or HOPA), a gene located at Xq13 that functions as a thyroid receptor-associated protein in the Mediator complex.

Contribution of retinoid X receptor signaling to the specification of skeletal muscle lineage.

Pluripotent stem cells possess a tremendous potential for the treatment of many diseases because of their capacity to differentiate into a variety of cell lineages. However, they provide little promise for muscle-related diseases, mainly because of the lack of small molecule inducers to efficiently direct myogenic conversion. Retinoic acid, acting through the retinoic acid receptor (RAR) and retinoid X receptor (RXR), affects stem cell fate determination in a concentration-dependent manner, but it only has a modest efficacy on the commitment of ES cells into skeletal muscle lineage. The RXR is very important for embryonic development but is generally considered to act as a silent partner of RAR in a non-permissive mode. In this study, we have examined whether activation of the RXR by rexinoid or RXR-specific signaling play a role in the specification of stem cells into muscle lineage. Our findings demonstrate that mouse ES cells generate skeletal myocytes effectively upon treatment with rexinoid at the early stage of differentiation and that on a molecular level, rexinoid-enhanced myogenesis simulates the sequential events observed in vivo. Moreover, RXR-mediated myogenic conversion requires the function of ß-catenin but not RAR. Our studies establish the feasibility of applying the RXR agonist in cell-based therapies to treat muscle-related diseases. The aptitude of mouse ES cells to generate skeletal myocytes following rexinoid induction also provides a model system to study the convergence of different signaling pathways in myogenesis.

Anticoagulation Therapy in Cancer Patients with Thrombosis in the Outpatient Sector of Germany (The CERTIFICAT Initiative)-German Practice of Anticoagulation Therapy of Cancer Patients with Thrombosis.

OBJECTIVE: This article aims to investigate the reality of anticoagulation treatment for cancer patients with thrombosis in the outpatient sector of Germany. METHODS: For the analysis period 2012 to 2015, anonymized data from 4.1 million statutory insured patients were analyzed. Cancer patients with incident thrombosis and an outpatient prescription of anticoagulant drugs were identified and evaluated for three subsequent quarters with regard to anticoagulant use. RESULTS: A total of 7,313 cancer patients with incident thrombosis (ICD-10: I80*) were evaluated. About, 90% of patients with thromboses were diagnosed and treated in the ambulatory sector. More than 80% of the prescriptions were issued by general practitioners. And 57% of patients were anticoagulated predominantly (>50% of the time) with different low-molecular-weight heparins (LMWHs), 24% predominantly with vitamin K antagonists (VKAs), and 17% with direct oral anticoagulants (DOACs). Anticoagulants were prescribed for an average of 4.5 months. LMWH had a substantially longer prescription period (90-135 days) than VKA (53 days) or DOAC (47 days). Gastrointestinal bleeding in conjunction with hospitalization was documented in 1.76% of patients with a range of 1.3 to 3% for the different LMWHs. CONCLUSION: The prescription practice documented by this representative and comprehensive evaluation demonstrates an anticoagulation duration in accordance with the guidelines, although the choice of the respective anticoagulant was often not in compliance with the contemporary label or guidelines.

Persistence With Biologic Therapy and Associated Costs of Patients With Inflammatory Bowel Disease: A German Retrospective Claims Data Analysis.

Background: In recent years, biologic agents became a relevant and promising treatment option for inflammatory bowel diseases (IBDs). However, high treatment costs and moderate remission rates lead to a high interest in treatment persistence and corresponding economic consequences. Methods: A retrospective health claims data analysis was conducted including biologic naive patients diagnosed with IBD between 2013 and 2018. Observation points were at 12 and 18 months of follow-up, starting from the first biologic prescription. Nonpersistence was defined as either no further prescription or prescription of another biologic agent within the days of supply per original prescription. Biologic agents included were Adalimumab, Golimumab, Infliximab, Ustekinumab, and Vedolizumab. Results: In total, 1444 patients with IBD were included in this analysis, mostly treated with Adalimumab (46.9%) and Infliximab (39.9%) as their first biologic treatment. After 12 months, 72.2% of patients were still persistent with their initial biologic treatment with the highest shares for Infliximab (74%) and Vedolizumab (72.4%). 27.8% of patients were nonpersistent, mostly due to a switch of biologic agent (75.8%). Cox regression identified female, hospitalizations, and simultaneous prescriptions of corticosteroids and immunomodulators as risk factors for nonpersistence. Treatment costs per year were approximately 3000€ higher for nonpersistent patients (27,146€) than for persistent patients (23,839€), mostly due to inpatient treatment costs. Conclusions: The persistence of biologic therapy in this study was rather high at 72% after 12 months, while nonpersistence was mostly due to switches to other biologic agents. Lack of persistence is associated with increased cost, mostly due to nonbiologic medication and inpatient treatment.

Spinal cord stimulation: a real-world data analysis on outcomes and differences between rechargeable and non-rechargeable implantable pulse generators.

OBJECTIVE: In this analysis, we examined differences between rechargeable and non-rechargeable spinal cord stimulation (SCS) devices in patients with pain. METHODS: We conducted a retrospective, longitudinal claims data analysis using a German research database comprising 5 million statutory insured patients (2012-2017). Outcomes of demographics, patient pathways, and health care resource utilization (HCRU) in patients with initial SCS were collected. RESULTS: Of 150 patients in the database, 73 (49%) received a rechargeable device and 77 (51%) a non-rechargeable device. The average age was 62.5 years (51% female and 49% male patients). A significant decrease over a 3-year follow-up was observed in analgesic prescriptions (-18%), number of patient visits to a physician, and number of patients who were hospitalized. HCRU-related figures for patients with non-rechargeable neurostimulators increased in the last follow-up year whereas the group receiving rechargeable neurostimulators showed a steady decrease. CONCLUSIONS: SCS seems to be an effective way for patients with chronic pain to decrease pain and improve quality of life. Rechargeable devices seem to be superior to non-rechargeable devices owing to greater longevity and were found to be associated with continuous reduction of pain diagnoses, hospitalization, physician visits, and use of pain medication in our study.

Severe multisystem pathology, metabolic acidosis, mitochondrial dysfunction, and early death associated with an X-linked AIFM1 variant.

Variants in the X-linked gene AIFM1 (apoptosis-inducing factor mitochondria-associated 1) are associated with a highly variable clinical presentation that encompasses motor neuropathy, ataxia, encephalopathies, deafness, and cognitive impairment. AIFM1 encodes a mitochondrial flavin adenine dinucleotide (FAD)-dependent nicotinamide adenine dinucleotide (NADH) oxidoreductase, with roles in the regulation of respiratory complex assembly and function, production of reactive oxygen species, and the coordination of a caspase-independent type of apoptosis known as parthanatos. In this report, we describe a missense AIFM1 variant (absent in reference population databases; c.506C > T, p.Pro169Leu) identified in the proband and sibling of a family with three affected males. The proband, his brother, and their maternal uncle all exhibited severe multisystem pathology, metabolic acidosis, and early demise. Metabolic testing on the proband revealed normal activity of the pyruvate dehydrogenase complex in skin fibroblasts. Absent or partial deficiency of cytochrome c oxidase was found in muscle fibers, however, supporting a Complex IV mitochondrial deficiency. Functional studies carried out on fibroblasts from the proband demonstrated reduced steady state levels of the AIFM1 protein, decreased Complex I subunit abundance, elevated sensitivity to the apoptosis inducer staurosporine, and increased nuclear condensation when grown in galactose-containing media. The reduced abundance of AIFM1 in the patient cells could not be stabilized with riboflavin or protease inhibitor treatment. Together, these findings suggest that the normal function of the AIFM1 gene product within mitochondria, and its response to apoptotic stimuli, are impaired by this variant, likely accounting for the severity of the phenotype seen in these patients. These findings also imply tissue-specific effects of this variant on different mitochondrial complexes. This study expands the genetic and phenotypic spectrum associated with AIFM1 variants, with the combination of exome sequencing and functional studies allowing a diagnosis to finally be confirmed for this family.