Newer Treatment Approaches in Pediatric-Onset Multiple Sclerosis

Multiple sclerosis in a 4-year-old boy: a case report and literature review

Pediatric onset multiple sclerosis (POMS) in the very young is a very rare entity and presents a difficult diagnostic challenge due to overlapping signs and symptoms with other diseases. We present a 4-year-old boy who initially presented with right-sided hemiparesis and demyelinating lesions on MRI. Follow-up MRI examinations 3 and 6 months later revealed new demyelinating lesions. Ten months after initial presentation, he presented with right-sided hemiparesis, central facial nerve palsy on the right side and new demyelinating lesions on MRI. Two clinical events and new MRI lesions on follow-up MRIs confirmed the diagnosis of POMS. He was treated with rituximab and experienced no further relapses or radiological progression during the follow-up period.

Neutrophil/lymphocyte and monocyte/lymphocyte indexes as potential predictors of relapse at 1 year after diagnosis of pediatric multiple sclerosis: a single-center, exploratory and proof-of-concept study

Introduction

Early identification of patients with a more unfavorable outcome in Multiple Sclerosis (MS) is crucial to optimize individualized treatment. Neutrophil-lymphocyte index (NLI) and monocyte-lymphocyte index (MLI) have been considered as potential biomarkers for disease prognosis. Our study aims to investigate the usefulness of NLI and MLI as predictors of relapse, disability progression, and lesion accumulation on magnetic resonance imaging (MRI) 1 year after diagnosis and treatment initiation, in pediatric-onset MS.

Methods

A retrospective single-center study was conducted, including patients with diagnosis of MS established in pediatric age (<18 years old), at least 1-year of follow-up, and a complete blood count (CBC) performed at diagnosis. We collected the nearest-to-diagnosis NLI and MLI, as well as clinical and imaging variables, at diagnosis and 12 months later. Our cohort was further dichotomized into two groups, based on the presence of relapses. Statistical significance was considered for p < 0.05.

Results

Eighteen patients (n = 18) were included. The relapsing group had higher mean, minimum, and maximum values for both NLI (5.17 ± 5.85, range: 1.57-11.92) and MLI (0.35 ± 0.22, range: 0.19-0.59), compared to the non-relapsing group (2.19 ± 1.63, range: 1.12-7.32 for NLI, and 0.24 ± 0.09, range: 0.14-0.44 for MLI). A higher percentage of patients in the relapsing group had increased NLI (>1.89, 66.7%) and MLI (>0.21, 66.7%) values than those in the non-relapsing group (46.7%). Patients who presented new T2-hyperintense lesions on MRI after 1 year of follow-up also had higher mean, minimum, and maximum values of both biomarkers. Patients who did not achieve No Evidence of Disease Activity-3 (NEDA-3) state exhibited higher values for both ratios. However, in our sample, no statistically significant correlations were found between MLI and NLI values and the clinical and imaging variables considered.

Conclusion

The ease of obtaining NLI and MLI from routine blood tests renders them useful biomarkers as a screening tool in longitudinal follow-up. Our study was based on a very small sample size, but it allowed us to verify the feasibility of the protocol used. It is intended to involve other centers in the next phase of this work, testing the possible usefulness of the indices under analysis on a larger sample.

The State of the Art of Pediatric Multiple Sclerosis

Multiple sclerosis (MS) represents a chronic immune-mediated neurodegenerative disease of the central nervous system that generally debuts around the age of 20-30 years. Still, in recent years, MS has been increasingly recognized among the pediatric population, being characterized by several peculiar features compared to adult-onset disease. Unfortunately, the etiology and disease mechanisms are poorly understood, rendering the already limited MS treatment options with uncertain efficacy and safety in pediatric patients. Thus, this review aims to shed some light on the progress in MS therapeutic strategies specifically addressed to children and adolescents. In this regard, the present paper briefly discusses the etiology, risk factors, comorbidities, and diagnosis possibilities for pediatric-onset MS (POMS), further moving to a detailed presentation of current treatment strategies, recent clinical trials, and emerging alternatives. Particularly, promising care solutions are indicated, including new treatment formulations, stem cell therapies, and cognitive training methods.

Demographic Features and Clinical Course of Patients With Pediatric-Onset Multiple Sclerosis on Newer Disease-Modifying Treatments

BACKGROUND

Treatment of pediatric-onset multiple sclerosis (POMS) is challenging given the lack of safety and efficacy data in the pediatric population for many of the disease-modifying treatments (DMTs) approved for use in adults with MS. Our objective was to describe the demographic features and clinical and radiologic course of patients with POMS treated with the commonly used newer DMTs within the US Network of Pediatric MS Centers (NPMSC).

METHODS

This is an analysis of prospectively collected data from patients who initiated treatment before age 18 with the DMTs listed below at the 12 regional pediatric MS referral centers participating in the NPMSC.

RESULTS

One hundred sixty-eight patients on dimethyl fumarate, 96 on fingolimod, 151 on natalizumab, 166 on rituximab, and 37 on ocrelizumab met criteria for analysis. Mean age at DMT initiation ranged from 15.2 to 16.5 years. Disease duration at the time of initiation of index DMT ranged from 1.1 to 1.6 years with treatment duration of 0.9-2.0 years. Mean annualized relapse rate (ARR) in the year prior to initiating index DMT ranged from 0.4 to 1.0. Mean ARR while on index DMT ranged from 0.05 to 0.20. New T2 and enhancing lesions occurred in 75%-88% and 55%-73% of the patients, respectively, during the year prior to initiating index DMT. After initiating index DMT, new T2 and enhancing lesions occurred in 0%-46% and 11%-34% patients, respectively. Rates of NEDA-2 (no evidence of disease activity) ranged from 76% to 91% at 6 months of treatment with index DMTs and 66% to 84% at 12 months of treatment with index DMTs.

CONCLUSIONS

Though limited by relatively short treatment duration with the index DMTs, our data suggest clinical and MRI benefit, as well as high rates of NEDA-2, in a large number of POMS patients, which can be used to guide future studies in this population.

Ocrelizumab in pediatric multiple sclerosis

BACKGROUND

Ocrelizumab is a recombinant humanized anti-CD20 monoclonal IgG1, approved by FDA and EMA for adult patients with multiple sclerosis (MS). The data on the efficacy and safety of Ocrelizumab for pediatric MS cases are limited.

OBJECTIVE

Here, we describe pediatric relapsing-remitting MS (P-RRMS) cases who were treated with Ocrelizumab as a disease-modifying drug.

METHOD

P-RRMS cases who were started Ocrelizumab below 18 years-of-age and followed-up >12 months with Ocrelizumab treatment were included. The primary end-points were annualized relapse rate (ARR) and magnetic resonance imaging (MRI) activity (new/enlarging T2 lesions and new gadolinium (Gd) enhancing lesions). The secondary end-points were the percentage of patients who remain relapse-free and/or free from Gd enhancing lesions, Expanded Disability Status Scale (EDSS) score, and the safety profile of Ocrelizumab.

RESULTS

Of 18 P-RRMS cases receiving Ocrelizumab, 10 patients fulfilled the inclusion criteria for our study. The median duration of follow-up under Ocrelizumab was 28,3 months (min: 15 months, max: 46 months). Mean ARR decreased from 2.01 (±0.71) to 0 during the follow-up of Ocrelizumab treatment (P < 0.0001). None of the patients had MRI activity during the treatment. Mean EDSS decreased from 1.75 (±1.09) to 1.20 (±0.63) from the initiation of Ocrelizumab to the last follow-up of the patients (P = 0.024). None of the patients had serious side effects, except one patient who experienced anaphylaxis.

CONCLUSION

Ocrelizumab can be considered a safe and effective treatment option in highly active P-RRMS.

First-line disease modifying treatments in pediatric-onset multiple sclerosis in Greece: therapy initiation at more advanced age is the main cause of treatment failure, in a retrospective observational study, with a cohort from a single Multiple Sclerosis Center

OBJECTIVES

Long-term immunomodulatory therapy of pediatric onset-multiple sclerosis (POMS) is based mainly on published case series and internationally agreed guidelines. Relevant studies in the Greek population are absent from the literature. The purpose of this study is to present data on the efficacy and safety of the 1st line immunomodulatory drugs in the treatment of POMS patients.

MATERIALS AND METHODS

The present study included 27 patients meeting the IPMSSG criteria for POMS and who are monitored at the outpatient clinic of the Multiple Sclerosis and Demyelinating Diseases Unit (MSDDU), of the 1st Neurological Department, University Hospital of Aeginition. All patients received 1st line immunomodulatory drugs as initial therapy. Clinical, laboratory, and imaging parameters of the disease were recorded before and after treatment.

RESULTS

Post-treatment, a significant reduction of the relapse number (mean ± SD: 2.0 ± 1.0 vs 1.2 ± 1.6, p = 0.002), EDSS progression (mean ± SD: 1.5 ± 0.8 vs 0.9 ± 0.7, p = 0.005) and ARR (mean ± SD: 1.5 ± 0.7 vs 0.4 ± 0.5, p = 0.0001) was observed, while no changes were observed in the EDSS score, (mean ± SD: 1.8 ± 0.6 vs 1.9. 0.6, p = 0.60). Advanced age at treatment initiation increased the risk for drug discontinuation before 24 months of therapy (HR = 0.6, 95% CI (0.35-0.99), p = 0.04).

CONCLUSIONS

Most pediatric patients are forced to switch to either more efficacious 1st line or 2nd line drugs. Additionally, our study suggests that older age at the time of the 1st line treatment initiation, contributes to earlier drug discontinuation.

Narrative review based on fingolimod therapy in pediatric MS

The course of pediatric-onset multiple sclerosis and adult multiple sclerosis shows some clinical differences. The rate of having a second attack after the first clinical event is 80% in children and around 45% in adults but the time to the second event is similar in all age groups. The pediatric group usually has a more aggressive onset than adults. On the other hand, a higher rate of complete recovery is observed in pediatric-onset multiple sclerosis after the first clinical event compared to the adult group. Despite a highly active initial disease course, pediatric-onset multiple sclerosis patients show a slower increase in disability than patients with adult-onset disease. This is thought to be due to greater remyelination capacity and plasticity of the developing brain. The management of pediatric-onset multiple sclerosis includes safety issues as well as effective disease control. In the pediatric-onset multiple sclerosis group, similar to adult multiple sclerosis, injectable treatments have been used for many years with reasonable efficacy and safety. Since 2011, oral treatments and then infusion treatments have been approved and used effectively in adult multiple sclerosis and have gradually entered clinical use in the pediatric-onset multiple sclerosis group. However, clinical trials are fewer, smaller, and include shorter follow-up due to the much lower prevalence of pediatric-onset multiple sclerosis than adult multiple sclerosis. This is particularly important in the era of recent disease-modifying treatments. This review of the literature presents existing data on the safety and efficacy of fingolimod, pointing to a relatively favorable profile.

The Economic and Humanistic Burden of Pediatric-Onset Multiple Sclerosis

Background: Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system. Pediatric-onset MS (POMS), defined as onset of MS before 18 years of age, is estimated to account for 2% to 5% of the MS population worldwide. Objectives: To conduct a literature review focused on the healthcare resource utilization and cost as well as quality-of-life (QOL) outcomes among patients with POMS. Methods: We conducted a systematic literature review of English-language studies published after September 2010 in MEDLINE and Embase to describe the global economic healthcare resource utilization and costs and humanistic (QOL) burden in patients with POMS. Results: We found 11 studies that reported on healthcare resource utilization, cost, or insurance coverage and 36 studies that reported on QOL outcomes in patients with POMS. Patients with POMS had higher rates of primary care visits (1.41 [1.29-1.54]), hospital visits (10.74 [8.95-12.90]), and admissions (rate ratio, 4.27 [2.92-6.25];OR, 15.2 [12.0-19.1]) compared with healthy controls. Mean per-patient costs in the United States were $5907 across all settings per year of follow-up between 2002 and 2012; mean costs per hospital stay were $38 543 (in 2015 USD) between 2004 and 2013. Three studies reported psychosocial scores between 71.59 and 79.7, and 8 studies reported physical health scores between 74.62 to 82.75 using the Pediatric Quality of Life Measurement Model (PedsQLTM). Twelve studies used the PedsQL™ Multidimensional Fatigue Scale. Mean scores on the self-reported general fatigue scale ranged from 63.15 to 78.5. Quality-of-life scores were lower than those of healthy controls. Discussion: Our review presents a uniquely broad and recent overview of the global economic and humanistic burden of patients with POMS. Additional research on healthcare resource utilization and cost would provide a more robust understanding of the economic burden in this population. Conclusions: Healthcare resource utilization and costs are high in this population, and patients report reduced QOL and significant fatigue compared with healthy children and adolescents.

Newer disease modifying treatments in pediatric onset multiple sclerosis: Experience from a single center

BACKGROUND

Disease modifying treatments (DMTs) for multiple sclerosis include injectable drugs (iDMTs) like interferons (IFNs) or glatiramer acetate (GA), and newer agents (nDMTs) in oral and intravenous forms. nDMTs are usually applied in escalation and less frequently as initial treatment in pediatric-onset (POMS).

OBJECTIVE

We intended to evaluate the effect of nDMTs in comparison with iDMTs by retrospective examination of our patients with POMS.

METHOD

Clinical records of POMS cases who received nDMTs either as escalation or initial treatment and who had at least 12 months' follow-up in our clinic were examined in two groups: patients who were started on iDMTs and later switched to nDMTs (Group A), and those who received nDMTs from the beginning (Group B). Presenting symptoms, annualized relapsing rate (ARR), recent Expanded Disability Status Scale (EDSS), lesion load and presence of contrast enhancing (CE) lesions on magnetic resonance imaging (MRI) were compared.

RESULTS

Total 43 patients were included: 33 in Group A and 10 in Group B. Age at onset, female/male ratio, duration since disease onset and duration under nDMT were similar in both groups. Initial involvement was predominantly brainstem and cerebellar in Group A and sensorial, brainstem/cerebellar, and optic nerve in Group B. The most frequently used nDMT was fingolimod in Group A (n = 17, 51.5%) and teriflunomide (n = 6, 60%) in Group B. Median ARR before any treatment was 2 in Group A and 1.5 in Group B (p > 0.05); it decreased to median 1 under iDMTs in Group A and to 0 under nDMTs. Mean follow-up was 6.7 ± 5 years (1-19, median 6 years) in Group A and 3.9 ± 3.7 years (range 1-12, median 2 years) in Group B. At the latest follow-up median EDSS scores were 1 in Group A and 0 in Group B. ARR had increased and lesion load on MRI went up progressively in both groups during follow-up. However, the rate of patients with CE lesions diminished in Group B.

CONCLUSION

This single-center study of POMS shows the ARR decreases under any treatment, more markedly under nDMTs, and nDMTs reduce the rate of patients with CE lesions on MRI without a clear effect on lesion load. The ARR tends to increase after the first 2 years of both iDMT and nDMT, suggesting a re-evaluation at that time. The ARR decreases shorty after treatment is changed from an iDMT to a nDMT.

Cognitive impairment in paediatric onset multiple sclerosis and its relation to thalamic volume and cortical thickness of temporal lobe by magnetic resonance imaging

Background

Pediatric onset multiple sclerosis (POMS), defined as an age at onset younger than 18 years, which occurs in 5% of patients with MS. cognitive dysfunction is one of the prominent disabling sequelae of Multiple sclerosis. Brain volumetric studies by magnetic resonance images revealed the decline of whole and regional brain volumes along the disease course. This work aimed to investigate the relationship between cognitive impairment in pediatric MS patients with thalamic atrophy and cortical thickness of temporal lobe. This study included 50 patients who were diagnosed as POMS and 50 healthy control participants matched for age and sex. Both groups were compared for volumetric measurements of thalamic volumes and temporal lobes cortical thickness using a computerized program called FreeSurfer.MS group was evaluated for cognitive dysfunction using Arabic version of fifth edition of Standford–Benit test. A correlation between volumetric results and neuropsychological evaluation of MS group was done.

Results

Our study showed that the MS group has the lowest value regarding their thalamic volumes and their cortical thickness of temporal lobes in relation to the healthy control group, while there was a significant relation between cognitive impairment and decrease in thalamic volume and specific areas in cortical thickness, such as superior temporal thickness, middle temporal thickness, inferior temporal thickness, fusiform thickness and para hippocampal thickness of temporal lobe in pediatric onset MS patients.

Conclusions

POMS affects specific brain areas such as thalamus and cortical thickness of temporal lobes regarding their volume and thickness which influence the neuropsychological evaluation detected by Standford–Benit test.

Improving pediatric multiple sclerosis interventional phase III study design: a meta-analysis

Background:

To support innovative trial designs in a regulatory setting for pediatric-onset multiple sclerosis (MS), the study aimed to perform a systematic literature review and meta-analysis of relapse rates with interferon β (IFN β), fingolimod, and natalizumab and thereby demonstrate potential benefits of Bayesian and non-inferiority designs in this population.

Methods:

We conducted a literature search in MEDLINE and EMBASE from inception until 17 June 2020 of all studies reporting annualized relapse rates (ARR) in IFN β-, fingolimod-, or natalizumab-treated patients with pediatric-onset relapsing–remitting MS. These interventions were chosen because the literature was mainly available for these treatments, and they are currently used for the treatment of pediatric MS. Two researchers independently extracted data and assessed study quality using the Cochrane Effective Practice and Organization of Care – Quality Assessment Tool. The meta-analysis estimates were obtained by Bayesian random effects model. Data were summarized as ARR point estimates and 95% credible intervals.

Results:

We found 19 articles, including 2 randomized controlled trials. The baseline ARR reported was between 1.4 and 3.7. The meta-analysis-based ARR was significantly higher in IFN β-treated patients (0.69, 95% credible interval: 0.51–0.91) versus fingolimod (0.11, 0.04–0.27) and natalizumab (0.17, 0.09–0.31). Based on the meta-analysis results, an appropriate non-inferiority margin versus fingolimod could be in the range of 2.29–2.67 and for natalizumab 1.72–2.29 on the ARR ratio scale. A Bayesian design, which uses historical information for a fingolimod or natalizumab control arm, could reduce the sample size of a new trial by 18 or 14 patients, respectively.

Conclusion:

This meta-analysis provides evidence that relapse rates are considerably higher with IFNs versus fingolimod or natalizumab. The results support the use of innovative Bayesian or non-inferiority designs to avoid exposing patients to less effective comparators in trials and bringing new medications to patients more efficiently.

Treatment of multiple sclerosis in children: A brief overview

Multiple sclerosis (MS) is the most common autoimmune, chronic inflammatory demyelinating disorder of the central nervous system. Pediatric-onset MS (POMS), as opposed to adult-onset MS (AOMS), is a rare condition, presenting similar clinical features to AOMS, but a more active course of the disease, with higher relapse rates and greater white and grey matter damage. To date, the therapeutic approaches to treat POMS have been extrapolated from observational studies and data from trials conducted on adults, raising concerns about their efficacy and safety in the pediatric population. Herein, we discuss the most common therapeutic strategies used in POMS management, basing on the individual clinical practice and experience.

Similarities and differences between multiple sclerosis and type 1 diabetes

Multiple sclerosis (MS) and type 1 diabetes (T1D) are chronic conditions that result from dysfunction of the immune system. Their common root in autoimmunity stimulates interest in the exploration of similarities and differences between the two diseases. Genetic susceptibility is relevant, creating a substrate, on which environmental factors act as a trigger of an aberrant immune response. Despite being both T-cell mediated disorders with a strong involvement of the humoral arm, immunomodulation is a mainstay of MS management, whereas hormone replacement therapy remains the principal approach for T1D. T1D is usually diagnosed in children and adolescents, while MS is typical of young adults. This difference has implications for disease progression and treatment. The SARS-CoV-2 pandemic and its effect on immunity may affect the prevalence of these conditions, as well as their clinical manifestation.

Teriflunomide: Pediatric First Approval

Teriflunomide (Aubagio^®), which was developed by Sanofi, is an oral immunomodulatory agent targeting the mitochondrial enzyme dihydroorotate dehydrogenase and available to adults to treat relapsing-remitting multiple sclerosis (MS). On 18 June 2021, teriflunomide received its first approval in this indication in pediatric patients aged ≥ 10 years in the EU. This article summarizes the milestones in the development of teriflunomide leading to this first pediatric approval for relapsing-remitting MS.

Shared Decision Making and Disease Modifying Therapy in Families of Children and Adolescents with Pediatric Onset Multiple Sclerosis

BACKGROUND

Deciding on a disease modifying therapy (DMT) for the treatment of pediatric onset multiple sclerosis (POMS) often presents a challenge to families. Parents are often overwhelmed by DMT choices, but they desire to be an integral part of the decision making process for their child. There is no standard approach for how best to involve families in this process. The aim of this study was to describe the experience of decision making related to the use of disease modifying therapy in parents of children and adolescents with POMS.

METHODS

The research aim was addressed using a descriptive survey design. Participants were recruited from the Pediatric MS and Related Disorders Program at Boston Children's Hospital as well as from the Pediatric Multiple Sclerosis Alliance online Facebook group.

RESULTS

Overall, fewer than half of parents felt very satisfied with the DMT they chose for their child with POMS (44%). Parental satisfaction with the decision making process increased with a high level of control of the process (p < 0.0001), satisfaction with communication (p < 0.0001), and feeling supported by the healthcare provider (p < 0.0001).

PRACTICE IMPLICATIONS

Healthcare providers should recognize the importance of the role of the family in the decision making process and how this directly impacts health outcomes. An open discussion at the time of DMT education should involve identification of family values and preferences. The use of online decision support tools have a valuable role in determining family preferences.

CONCLUSION

There is an opportunity of healthcare providers to foster shared decision making practices to improve satisfaction among parents of children and adolescents with POMS. Healthcare providers should work closely with families to identify and incorporate their personal preferences for their role in the decision making process. Future research should include the testing of decision support tools for decision making in POMS.

Early age of onset predicts severity of visual impairment in patients with neuromyelitis optica spectrum disorder

BACKGROUND

Severe residual visual loss (SRVL) is frequent in neuromyelitis optica spectrum disorders (NMOSD). Identifying higher-risk patients at onset is important to prevent disability accumulation.

OBJECTIVE

To determine predictors of SRVL in a large NMOSD cohort.

METHODS

Patient characteristics at last visual acuity (VA) evaluation were retrospectively collected. VA was scored 0: better than 20/40, 1: 20/40-20/99, 2: 20/100-20/200, and 3: worse than 20/200. SRVL was defined as a combined score (VA worst + best eye) ⩾ 4. Descriptive statistics were used to compare groups and logistic regression to evaluate predictors of VA.

RESULTS

106 patients (mean age at disease onset (AO): 35.8 ± 16.5 years) were included. Patients with SRVL had earlier AO (mean: 26.7 vs 38.0 years) compared to non-SRVL group (p = 0.005). Patients with AO < 21 years were more likely to have SRVL, be blind, present with binocular optic neuritis, have recurrent optic neuritis, and receive oral therapy first-line than those with AO ⩾ 21. After adjusting for race, sex, and disease duration, the odds of SRVL were 4.68 times higher in patients < 21 at disease onset (95% CI: 1.53-14.34, p = 0.007).

CONCLUSION

Early AO predicts SRVL in NMOSD, independent of disease duration. High-efficacy therapies should be considered for first-line treatment in this group.

Current Advances in Pediatric Onset Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune inflammatory disease affecting the central nervous system leading to demyelination. MS in the pediatric population is rare, but has been shown to lead to significant disability over the duration of the disease. As we have learned more about pediatric MS, there has been a development of improved diagnostic criteria leading to earlier diagnosis, earlier initiation of disease-modifying therapies (DMT), and an increasing number of DMT used in the treatment of pediatric MS. Over time, treatment with DMT has trended towards the initiation of higher efficacy treatment at time of diagnosis to help prevent further disease progression and accrual of disability over time, and there is evidence in current literature that supports this change in treatment patterns. In this review, we discuss the current knowledge in diagnosis, treatment, and clinical outcomes in pediatric MS.

Germline Genetic Risk Variants for Progressive Multifocal Leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disorder of the brain caused by reactivation of the JC virus (JCV), a polyomavirus that infects at least 60% of the population but is asymptomatic or results in benign symptoms in most people. PML occurs as a secondary disease in a variety of disorders or as a serious adverse event from immunosuppressant agents, but is mainly found in three groups: HIV-infected patients, patients with hematological malignancies, or multiple sclerosis (MS) patients on the immunosuppressant therapy natalizumab. It is severely debilitating and is deadly in ~50% HIV cases, ~90% of hematological malignancy cases, and ~24% of MS-natalizumab cases. A PML risk prediction test would have clinical utility in all at risk patient groups but would be particularly beneficial in patients considering therapy with immunosuppressant agents known to cause PML, such as natalizumab, rituximab, and others. While a JC antibody test is currently used in the clinical decision process for natalizumab, it is suboptimal because of its low specificity and requirement to periodically retest patients for seroconversion or to assess if a patient's JCV index has increased. Whereas a high specificity genetic risk prediction test comprising host genetic risk variants (i.e., germline variants occurring at higher frequency in PML patients compared to the general population) could be administered one time to provide clinicians with additional risk prediction information that is independent of JCV serostatus. Prior PML case reports support the hypothesis that PML risk is greater in patients with a genetically caused immunodeficiency disorder. To identify germline PML risk variants, we performed exome sequencing on 185 PML cases (70 in a discovery cohort and 115 in a replication cohort) and used the gnomAD variant database for interpretation. Our study yielded 19 rare variants (maximum allele frequency of 0.02 in gnomAD ethnically matched populations) that impact 17 immune function genes (10 are known to cause inborn errors of immunity). Modeling of these variants in a PML genetic risk test for MS patients considering natalizumab treatment indicates that at least a quarter of PML cases may be preventable.