A Comprehensive, Targeted NGS Approach to Assessing Molecular Diagnosis of Lysosomal Storage Diseases.

Valentina La Cognata,Sebastiano Cavallaro

doi:10.3390/genes12111750

Abstract

With over 60 different disorders and a combined incidence occurring in 1:5000–7000 live births, lysosomal storage diseases (LSDs) represent a major public health problem and constitute an enormous burden for affected individuals and their families. Several reasons make the diagnosis of LSDs an arduous task for clinicians, including the phenotype and penetrance variability, the shared signs and symptoms, and the uncertainties related to biochemical enzymatic assay results. Developing a powerful diagnostic tool based on next generation sequencing (NGS) technology may help reduce the delayed diagnostic process for these families, leading to better outcomes for current therapies and providing the basis for more appropriate genetic counseling. Herein, we employed a targeted NGS-based panel to scan the coding regions of 65 LSD-causative genes. A reference group sample (n = 26) with previously known genetic mutations was used to test and validate the entire workflow. Our approach demonstrated elevated analytical accuracy, sensitivity, and specificity. We believe the adoption of comprehensive targeted sequencing strategies into a routine diagnostic route may accelerate both the identification and management of LSDs with overlapping clinical profiles, producing a significant reduction in delayed diagnostic response with beneficial results in the treatment outcome.

Highlights

Lysosomal storage disorders (LSDs) are rare inherited diseases characterized by the accumulation of specific undegraded metabolites inside the lysosomes [1,2,3]
Both the considerable clinical variability within each disease phenotype and the overlapping symptomatology among single LSDs hamper the path for a precise diagnosis, which often involves a delay in treatment and severe consequences on patients’ quality of life and their families [4]
Current diagnostic workflows include an accurate evaluation of both medical history and clinical presentations, which lead to the formulation of suspicion of one or more LSDs, followed by biochemical analysis to quantify either the accumulated storage product or the enzymatic activity in leukocytes, fibroblasts, urine, or rehydrated dried blood spots (DBS)

Summary

Introduction

Lysosomal storage disorders (LSDs) are rare inherited diseases characterized by the accumulation of specific undegraded metabolites inside the lysosomes [1,2,3] This overstorage is commonly caused by a deficiency or absent activity of lysosomal hydrolases or, in a few cases, by the deficit of further non-enzymatic lysosomal proteins (such as integral membrane proteins) [3]. Clinical signs and symptoms may occur from the prenatal period to adulthood and may develop progressively over time, leading to a wide spectrum of disease phenotypes from mild to extremely severe forms that involve neuropathological effects, psychomotor development delay, cognitive decline, musculoskeletal abnormalities, dysmorphia, organomegaly, and seizures [6] Both the considerable clinical variability within each disease phenotype and the overlapping symptomatology among single LSDs hamper the path for a precise diagnosis, which often involves a delay in treatment and severe consequences on patients’ quality of life and their families [4]. Current diagnostic workflows include an accurate evaluation of both medical history and clinical presentations, which lead to the formulation of suspicion of one or more LSDs, followed by biochemical analysis to quantify either the accumulated storage product or the enzymatic activity in leukocytes, fibroblasts, urine, or rehydrated dried blood spots (DBS)

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