Clinical characteristics of adult patients with inborn errors of metabolism in Spain: A review of 500 cases from university hospitals

Lysosomal storage disorders identified in adult population from India: Experience of a tertiary genetic centre and review of literature

Lysosomal storage disorders (LSDs) in adults have milder phenotype and variable age at presentation. Several studies have described the phenotype, genotype and treatment outcomes for adult-onset LSDs like Gaucher, Fabry, Pompe disease and others. We describe the first systematic study on the occurrence of LSDs in an adult population from India. It describes, the key clinical signs seen in these patients and those from literature review that can aid in early detection. Of 2102 biochemically diagnosed LSDs cases, 32 adult patients were identified with LSDs. Based on the clinical suspicion, screening test and enzyme study was carried out. Twenty-two patients were subjected to a genetic study to identify the causative variant in a respective gene. Of the 32 adult patients, we observed a maximum percentage of 37.5% (n = 12) cases with Gaucher disease, followed by 13% (n = 4) with Fabry disease. We found 10% of cases with MPS IVA and MPS I, and 9% cases with Pompe. Single case of adult mucolipidosis III and two cases each of Type 1 Sialidosis, Niemann-Pick disease B and metachromatic leukodystrophy were identified. We observed two common variants p.Leu483Pro and p.Ala487Thr in the GBA1 gene in 23% of Indian patients with adult Gaucher disease. No common variants were observed in other aforementioned LSDs. Study identified 50% of Fabry patients and 4% of Gaucher patients diagnosed at our centre to be adults. The prevalence of adult Pompe patients was low (3.4%) as compared to 80% reported in the Caucasian population. Adult LSDs such as, MPS III, GM1/GM2 gangliosidosis and Krabbe disease were not identified in our cohort.

Inherited metabolic disorders in adults: systematic review on patient characteristics and diagnostic yield of broad sequencing techniques (exome and genome sequencing)

BACKGROUND/OBJECTIVES

The timely diagnosis of inherited metabolic disorders (IMD) is essential for initiating treatment, prognostication and genetic testing of relatives. Recognition of IMD in adults is difficult, because phenotypes are different from those in children and influenced by symptoms from acquired conditions. This systematic literature review aims to answer the following questions: (1) What is the diagnostic yield of exome/genome sequencing (ES/GS) for IMD in adults with unsolved phenotypes? (2) What characteristics do adult patients diagnosed with IMD through ES/GS have?

METHODS

A systematic search was conducted using the following search terms (simplified): "Whole exome sequencing (WES)," "Whole genome sequencing (WGS)," "IMD," "diagnostics" and the 1,450 known metabolic genes derived from ICIMD. Data from 695 articles, including 27,702 patients, were analyzed using two different methods. First, the diagnostic yield for IMD in patients presenting with a similar phenotype was calculated. Secondly, the characteristics of patients diagnosed with IMD through ES/GS in adulthood were established.

RESULTS

The diagnostic yield of ES and/or GS for adult patients presenting with unexplained neurological symptoms is 11% and for those presenting with dyslipidemia, diabetes, auditory and cardiovascular symptoms 10, 9, 8 and 7%, respectively. IMD patients diagnosed in adulthood (n = 1,426), most frequently portray neurological symptoms (65%), specifically extrapyramidal/cerebellar symptoms (57%), intellectual disability/dementia/psychiatric symptoms (41%), pyramidal tract symptoms/myelopathy (37%), peripheral neuropathy (18%), and epileptic seizures (16%). The second most frequently observed symptoms were ophthalmological (21%). In 47% of the IMD diagnosed patients, symptoms from multiple organ systems were reported. On average, adult patients are diagnosed 15 years after first presenting symptoms. Disease-related abnormalities in metabolites in plasma, urine or cerebral spinal fluid were identified in 40% of all patients whom underwent metabolic screening. In 52% the diagnosis led to identification of affected family members with the same IMD.

CONCLUSION

ES and/or GS is likely to yield an IMD diagnosis in adult patients presenting with an unexplained neurological phenotype, as well as in patients with a phenotype involving multiple organ systems. If a gene panel does not yield a conclusive diagnosis, it is worthwhile to analyze all known disease genes. Further prospective research is needed to establish the best diagnostic approach (type and sequence of metabolic and genetic test) in adult patients presenting with a wide range of symptoms, suspected of having an IMD.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier: CRD42021295156.

Adults with lysosomal storage diseases in the undiagnosed diseases network

OBJECTIVES

To review the referral and clinical characteristics of adult patients diagnosed with lysosomal storage diseases (LSD) through the Undiagnosed Diseases Network (UDN).

METHODS

Retrospective review of both application and evaluation records for adults admitted to the UDN with a final diagnosis of a lysosomal storage disease.

RESULTS

Ten patients were identified. Final diagnoses included late onset Tay Sachs, attenuated MPS I, MPS IIIA, MPS IIIB, and MPS IIIC. Most patients presented with neurocognitive changes. Prior to referral, all patients had been evaluated by neurology, four patients underwent phenotype specific panel testing that did not include the causative gene, and four patients had non-diagnostic clinical exome sequencing.

CONCLUSIONS

LSDs figure highly in the differential diagnosis of neurometabolic disorders in pediatric onset progressive diseases. In adults, their subtle initial presentations overlap with symptoms of more common disorders and less practitioner awareness may lead to prolonged diagnostic challenges.

Multidisciplinary Care of Patients with Inherited Metabolic Diseases and Epilepsy: Current Perspectives

More than 650 inherited metabolic diseases may present with epilepsy or seizures. These diseases are often multisystem, life-long and induce complex needs of patients and families. Multidisciplinary care involves all stages of disease management: diagnostics, specific or symptomatic, acute and chronic treatments, and integrated care that takes into account not only medical, but also manifold psychosocial, educational, vocational and other needs of patients and their caregivers. Care coordination is indispensable to ensure smooth transitions of care across life and disease stages, including management of emergencies, transition from pediatric to adult services and palliative care. Care pathways are highly diverse and have to find the right balance between highly specialized and locally provided services. While multidisciplinary teams consist of many professionals, a named supervising physician in a highly specialized healthcare setting and a care coordinator are highly important. As the greatest burden of care always falls onto the shoulders of patients and/or families, patient empowerment should be a part of every care pathway and include provision of required information, involvement into common decision-making, patient’s and family’s education, support for self-management, liaison with peer support groups and emotional/ psychological support. Due to the rarity and complexity of these diseases, sufficient expertise may not be available in a national healthcare system and cross-border services (virtual or physical) in the recently developed European Reference Networks should be ensured through the proper organization of referral systems in each EU and EEA country. Finally, digital technologies are particularly important in the provision of services for patients with rare diseases and can significantly increase the availability of highly specialized services and expertise.

The diagnosis of inborn errors of metabolism in previously undiagnosed adults referred for medical genetics evaluation

Traditionally thought of as a pediatric diagnostic and therapeutic dilemma, the diagnostic rate and spectrum of inborn errors of metabolism (IEM) in the adult population is largely unknown. A retrospective chart review of patients seen by the Michigan Medicine Adult Medical Genetics Clinic for clinical evaluation from 2014 to 2018 was conducted. Patients referred for a primary indication possibly consistent with an IEM were considered. Variables included age at genetic evaluation, symptom onset age, sex, clinical course, organ systems involved, developmental history, family history and prior genetic testing. Of patients evaluated during the study period, 112 were referred for an indication possibly consistent with an IEM and underwent a complete biochemical workup with an IEM diagnostic rate of 9.8% achieved. An additional 9.8% were diagnosed with a non-IEM genetic diagnosis. Management changes were implemented in all IEM diagnoses. Metabolic disorders in the adult population are under-recognized and under-diagnosed. This report demonstrates the need for clinicians to consider these diagnoses in adults and either refer to a genetics clinic or initiate a biochemical workup. As advances in diagnosis, treatment, and life expectancy of patients with IEMs increases, recognizing and diagnosing these conditions can significantly impact care.

Clouds over IMD? Perspectives for inherited metabolic diseases in adults from a retrospective cohort study in two Swiss adult metabolic clinics

Background

Inherited metabolic diseases (IMD) are complex medical conditions. Thanks to improvements in diagnosis and treatment, a growing number of pediatric IMD patients reach adulthood. Thus, clinical care of adults with IMD has emerged as a new and challenging reality. This purpose of this study of adults with IMD in an adult metabolic clinic at two academic hospitals (Lausanne and Geneva) was to help inform decisions on the future organization of health care for this group of patients.

Methods

All adult patients with a biochemical and/or genetic diagnosis of IMD followed at the clinics were included in the study. Electronic patient records were reviewed for clinical features, diagnostic studies, treatment and long-term outcome. Data of undiagnosed patients referred for suspected IMD were analyzed separately.

Results

126 patients were included in the study. The most prevalent group of diseases was small molecules disorders with 82 (65%) patients, followed by energy defects disorders with 29 (23%) patients and complex molecules disorders with 15 (12%) patients. Overall, 64% of patients were diagnosed before, and 36% after the age 16 years. Among the 126 cases, 51% suffered from medical complications. 79% of the patients were receiving a specific treatment for their disease. Among the 138 undiagnosed patients referred for suspicion of IMD, investigations lead to a genetic diagnosis in 24 (17%) patients. 19 had confirmation of an IMD, 5 were found to have another genetic condition.

Conclusions

This retrospective study reveals significant features of adult IMD cohort. The disorders are heterogeneous, and there is no one-size-fits-all approach – treatment must be tailored to fit each specific disorder in each individual patient. Even patients who are followed at the dedicated clinic are not protected from metabolic decompensations and/or chronic organ-specific complications. While it is commonly assumed that patients with IMD are more stable once they become adults, our data show that the diseases continue to exact a lifelong toll. A coordinated monitoring of target organs by a multidisciplinary team is needed. To ensure that the success in diagnosis and treatment of individuals with IMD is sustained, there is a clear requirement for adequately staffed adult IMD clinics.

[Diagnostic journey of type 1 Gaucher Disease patients: A survey including internists and hematologists]

INTRODUCTION

Gaucher disease (GD) is a rare genetic lysosomal storage disorder caused by a beta-glucocerebrosidase deficiency and responsible for a lysosomal storage disorder. GD is characterized by haematological, visceral and bone involvements. The aim of this study was to describe the diagnostic journey of type 1 GD patients as well as the role of the internist.

METHODS

A retrospective multicentric study involving type 1 GD patients has been conducted in 16 centers, between 2009 and 2011.

RESULTS

Fifty-five type 1 GD patients were included, under the care of an internist or an haematologist. They were originally hospitalized in 8 different specialized units. Diagnosis was established by bone-marrow aspiration in 22 patients (40%), by enzymatic assay of glucocerebrosidase activity in 15 patients (27%), and by bone-marrow biopsy in 9 patients (16%). The use of enzymatic assay became more frequent after 1990. The delay between first hospitalization due to GD symptoms and definitive diagnosis was less than one year for 38 patients. Patients with suspected GD were mainly referred to an internist physician.

CONCLUSION

GD seems to be better recognized and quickly diagnosed since 1990 in spite of the multiplicity of journeys. The role of the internist seems important.

Modifier genes: Moving from pathogenesis to therapy

This commentary will focus on how we can use our knowledge about the complexity of human disease and its pathogenesis to identify novel approaches to therapy. We know that even for single gene Mendelian disorders, patients with identical mutations often have different presentations and outcomes. This lack of genotype-phenotype correlation led us and others to examine the roles of modifier genes in the context of biological networks. These investigations have utilized vertebrate and invertebrate model organisms. Since one of the goals of research on modifier genes and networks is to identify novel therapeutic targets, the challenges to patient access and compliance because of the high costs of medications for rare genetic diseases must be recognized. A recent article explored protective modifiers, including plastin 3 (PLS3) and coronin 1C (CORO1C), in spinal muscular atrophy (SMA). SMA is an autosomal recessive deficit of survival motor neuron protein (SMN) caused by mutations in SMN1. However, the severity of SMA is determined primarily by the number of SMN2 copies, and this results in significant phenotypic variability. PLS3 was upregulated in siblings who were asymptomatic compared with those who had SMA2 or SMA3, but identical homozygous SMN1 deletions and equal numbers of SMN2 copies. CORO1C was identified by interrogation of the PLS3 interactome. Overexpression of these proteins rescued endocytosis in SMA models. In addition, antisense RNA for upregulation of SMN2 protein expression is being developed as another way of modifying the SMA phenotype. These investigations suggest the practical application of protective modifiers to rescue SMA phenotypes. Other examples of the potential therapeutic value of novel protective modifiers will be discussed, including in Duchenne muscular dystrophy and glycerol kinase deficiency. This work shows that while we live in an exciting era of genomic sequencing, a functional understanding of biology, the impact of its disruption, and possibilities for its repair have never been more important as we search for new therapies.