Twenty- five years of biochemical diagnosis of Gaucher disease: the Egyptian experience

What should rheumatologists know about Gaucher disease and Fabry disease? Connecting the dots for an overview

Gaucher and Fabry diseases are lysosomal storage disorders in which deficient enzyme activity leads to pathological accumulation of sphingolipids. These diseases have a broad phenotypic presentation. Musculoskeletal symptoms and pain complaints are frequently reported by patients. Thus, rheumatologists can be contacted by these patients, contributing to the correct diagnosis, earlier indication of appropriate treatment and improvement of their prognosis. This review describes important concepts about Gaucher and Fabry diseases that rheumatologists should understand to improve patients' quality of life and change the natural history of these diseases.

Exploring the efficacy and safety of Ambroxol in Gaucher disease: an overview of clinical studies

Gaucher disease (GD) is mainly caused by glucocerebrosidase (GCase) enzyme deficiency due to genetic variations in the GBA1 gene leading to the toxic accumulation of sphingolipids in various organs, which causes symptoms such as anemia, thrombocytopenia, hepatosplenomegaly, and neurological manifestations. GD is clinically classified into the non-neuronopathic type 1, and the acute and chronic neuronopathic forms, types 2 and 3, respectively. In addition to the current approved GD medications, the repurposing of Ambroxol (ABX) has emerged as a prospective enzyme enhancement therapy option showing its potential to enhance mutated GCase activity and reduce glucosylceramide accumulation in GD-affected tissues of different GBA1 genotypes. The variability in response to ABX varies across different variants, highlighting the diversity in patients' therapeutic outcomes. Its oral availability and safety profile make it an attractive option, particularly for patients with neurological manifestations. Clinical trials are essential to explore further ABX's potential as a therapeutic medication for GD to encourage pharmaceutical companies' investment in its development. This review highlights the potential of ABX as a pharmacological chaperone therapy for GD and stresses the importance of addressing response variability in clinical studies to improve the management of this rare and complex disorder.

Patient centered guidelines for the laboratory diagnosis of Gaucher disease type 1

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder due to the deficient activity of the acid beta-glucosidase (GCase) enzyme, resulting in the progressive lysosomal accumulation of glucosylceramide (GlcCer) and its deacylated derivate, glucosylsphingosine (GlcSph). GCase is encoded by the GBA1 gene, located on chromosome 1q21 16 kb upstream from a highly homologous pseudogene. To date, more than 400 GBA1 pathogenic variants have been reported, many of them derived from recombination events between the gene and the pseudogene. In the last years, the increased access to new technologies has led to an exponential growth in the number of diagnostic laboratories offering GD testing. However, both biochemical and genetic diagnosis of GD are challenging and to date no specific evidence-based guidelines for the laboratory diagnosis of GD have been published. The objective of the guidelines presented here is to provide evidence-based recommendations for the technical implementation and interpretation of biochemical and genetic testing for the diagnosis of GD to ensure a timely and accurate diagnosis for patients with GD worldwide. The guidelines have been developed by members of the Diagnostic Working group of the International Working Group of Gaucher Disease (IWGGD), a non-profit network established to promote clinical and basic research into GD for the ultimate purpose of improving the lives of patients with this disease. One of the goals of the IWGGD is to support equitable access to diagnosis of GD and to standardize procedures to ensure an accurate diagnosis. Therefore, a guideline development group consisting of biochemists and geneticists working in the field of GD diagnosis was established and a list of topics to be discussed was selected. In these guidelines, twenty recommendations are provided based on information gathered through a systematic review of the literature and two different diagnostic algorithms are presented, considering the geographical differences in the access to diagnostic services. Besides, several gaps in the current diagnostic workflow were identified and actions to fulfill them were taken within the IWGGD. We believe that the implementation of recommendations provided in these guidelines will promote an equitable, timely and accurate diagnosis for patients with GD worldwide.

A rare homozygous p.Arg87Trp variant of the GBA gene in Gaucher disease: A case report

Gaucher disease (GD) is a rare metabolic disorder due to pathogenic variants in the GBA gene. We report the first case of the rare p.Arg87Trp pathogenic variant (formerly known as R48W) of the GBA gene in the Tunisian population. A female Arab patient was assessed at the age of 26 due to abdominal distension, bone pain, and headache since she was 25. Physical examination revealed splenomegaly, rib deformation, lumbar scoliosis, and upper limb tremor. Bone marrow was infiltrated by Gaucher cells. The patient was homozygous for the rare p.Arg87Trp variant which is known to be associated with a mild phenotype. This report highlights the necessity of screening the Tunisian population for this rare variant.

Gaucher disease is the most common inherited lysosomal storage disorder. It is a multisystem condition resulting from glucocerebrosidase deficiency, with high inter‐ and intrafamilial phenotypic variability. Gaucher disease patients can be eligible for enzymatic replacement therapy. Therefore, it should be suspected in adults presenting with unexplained splenomegaly and skeletal deformities.

Enzyme Sensing Using 2-Mercaptopyridine-Carbonitrile Reporters and Surface-Enhanced Raman Scattering

The high sensitivity and functional group selectivity of surface-enhanced Raman scattering (SERS) make it an attractive method for enzyme sensing, but there is currently a severe lack of enzyme substrates that release SERS reporter molecules with favorable detection properties. We find that 2-mercaptopyridine-3-carbonitrile ( o-MPN) and 2-mercaptopyridine-5-carbonitrile ( p-MPN) are highly effective as SERS reporter molecules that can be captured by silver or gold nanoparticles to give intense SERS spectra, each with a distinctive nitrile peak at 2230 cm-1. p-MPN is a more sensitive reporter and can be detected at low nanomolar concentrations. An assay validation study synthesized two novel substrate molecules, Glc-o-MPN and Glc-p-MPN, and showed that they can be cleaved efficiently by β-glucosidase (K m = 228 and 162 μM, respectively), an enzyme with broad industrial and biomedical utility. Moreover, SERS detection of the released reporters ( o-MPN or p-MPN) enabled sensing of β-glucosidase activity and β-glucosidase inhibition. Comparative experiments using a crude almond flour extract showed that the presence of β-glucosidase activity could be confirmed by SERS detection in a much shorter time period (>10 time shorter) than by UV-vis absorption detection. It is likely that a wide range of enzyme assays and diagnostic tests can be developed using 2-mercaptopyridine-carbonitriles as SERS reporter molecules.

Mucopolysaccharidoses diagnosis in the era of enzyme replacement therapy in Egypt

BACKGROUND

Undegraded glycosaminoglycans (GAGs) induced by deficiency of enzymes are the primary cause of mucopolyscchardoses. Mucopolysacchardoses (MPS) are a group of rare lysosomal storage diseases (LSD). The quantification of a specific enzymatic activity is needed for accurate diagnosis. The objectives of this work were: first, to continue the study of mucopolysacchardoses disease in Egypt after the start of using the enzyme replacement therapy (ERT). Second, to define the commonest types among our population after 18 years experience with the disease. Third, to compare the different MPS types' distribution, diagnosed after the start of the ERT, to identify the impact of using ERT on the number and type of diagnosed patients.

METHOD

Urinary GAGs were measured for all referred cases followed by two-dimensional electrophoretic separation for cases with high levels of GAGs; the specific enzyme activity was assayed for each type depending on the abnormal electrophoretic pattern obtained. Clinically suspected cases of Morquio syndrome were directly subjected to measuring the specific enzyme.

RESULTS

Out of 1448 suspected cases, 622 (42.9%) MPS patients were diagnosed revealing the following distribution: MPS I (172, 27.7%), MPS II (57, 9.1%), MPS III [(177, 28.5%: 134 type B and 43 types A, C or D)], MPS IVA (124, 19.9%), MPS VI (90, 14.5%) and MPS VII (2, 0.3%). MPS III was the most commonly diagnosed type followed by MPS I and MPS IVA. MPS IVA represented the most common type receiving treatment, followed by MPS I, MPS II and MPS VI.

CONCLUSION

The presence of treatment encouraged the affected families and physicians to seek diagnosis. MPS III was the commonest type among our studied group after 7 years of diagnosis, while MPS IVA was the commonest type receiving treatment.

Cytogenetic and Biochemical Genetic Techniques for Personalized Drug Therapy in Europe

For many authorized drugs, accumulating scientific evidence supports testing for predictive biomarkers to apply personalized therapy and support preventive measures regarding adverse drug reactions and treatment failure. Here, we review cytogenetic and biochemical genetic testing methods that are available to guide therapy with drugs centrally approved in the European Union (EU). We identified several methods and combinations of techniques registered in the Genetic Testing Registry (GTR), which can be used to guide therapy with drugs for which pharmacogenomic-related information is provided in the European public assessment reports. Although this registry provides information on genetic tests offered worldwide, we identified limitations regarding standard techniques applied in clinical practice and the information on test validity rarely provided in the according sections.

Diffusion tensor imaging of vertebral bone marrow in children with Gaucher's disease type I and III: Pre- and post-therapy

PURPOSE

To assess diffusion tensor imaging (DTI) of the vertebral bone marrow (BM) in children with Gaucher's disease (GD) types I and III before and after therapy.

METHODS

Prospective study was conducted upon 25 children with GD type I (n = 17) and III (n = 8) and 13 age and sex-matched controls underwent DTI of vertebral BM. Mean diffusivity (MD) and fractional anisotropy (FA) of vertebral BM was calculated and correlated with genotyping, chitotriosidase, hemoglobin (HB) and, platelet count.

RESULTS

There was a statistically significant difference in MD and FA of BM between patients and controls (P = 0.001 and 0.02). The area under the curve (AUC) of MD and FA used to differentiate untreated patients from controls was 0.902 and 0.68 with sensitivity, specificity, and, accuracy 92%, 84.6%, and, 89.5% respectively. There was a significant difference in MD and FA of BM between untreated and treated patients (P = 0.001 and 0.02). AUC of MD and FA used to differentiate untreated from treated patients was 0.93 and 0.649 with sensitivity, specificity, and accuracy of 92%, 80%, and 86% respectively. There was a significant difference in MD and FA (P = 0.03, 0.001 respectively) of BM in GD with homozygous L444P mutation (n = 9) and other mutations (n = 14). Chiotriptase, HB and platelet count of patients was correlated with MD (r = -0.36, 0.42, -0.41) and FA (r = -0.47, -0.37, -0.46) respectively.

CONCLUSION

DTI of vertebral BM can help in diagnosis and monitoring patients with GD after therapy and correlated with genotyping, and hematological biomarkers of GD.

Gaucher Disease Type I: A Case Report

Gaucher disease (GD) is a multi-systemic disease with a low population frequency. It is a lysosomal storage disorder (LSD) that causes accumulation of glucocerebroside in the so called Gaucher cells predominantly in areas like the spleen, liver and bone marrow. Type I GD (GDI) is the most common form and usually does not involve the brain and the spinal cord. The symptoms can range from mild to severe and may appear anytime from childhood to adulthood. Diagnostics can often be challenging and imposes looking at person’s medical history, symptoms, physical exam, and laboratory test results. We present a difficult to diagnose case of a 34-year-old woman admitted to the Clinic of Hematology, “Sv. I. Rilski” hospital with splenomegaly, normal laboratory findings and non-enlarged liver. She didn’t show focal neurological symptoms. A series of tests were assigned including genetic targeted analysis. The case is an example of a rare genetic disease with mild clinical symptoms. Diagnosis of Gaucher disease, type I was confirmed by measurement of a GBA enzyme activity and identification of mutations in the GBA gene inherited in an autosomal recessive manner. Thanks to the efforts of the clinical team, the assignment of adequate clinical and laboratory tests and their correct interpretation, the patient was subjected to enzyme replacement therapy (ERT). Although the diagnosis was settled relatively late (at 34 years of age), the correct therapy slowed down the invalidation and improved the quality of life of the patient.