Nine-year experience in Gaucher disease diagnosis at the Spanish reference center Fundación Jiménez Díaz

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.

Genotype/phenotype relationship in Gaucher disease patients. Novel mutation in glucocerebrosidase gene

Objectives Gaucher disease (GD) is the most common inherited lysosomal storage disease, caused by mutations in acid β-glucosidase (GBA) gene. This study aimed to identify mutations in Andalusia patients with GD and their genotype-phenotype correlation. Methods Descriptive observational study. University Hospital Virgen del Rocio patients diagnosed from GD from 1999 to 2019 were included. Demographic and clinical data, β-glucocerebrosidase activity, variants pathogenic in GBA gene and biomarkers for monitoring treatment were collected from digital medical record. Results Twenty-six patients with aged between 1 day and 52 years were studied. A total of six mutations described as pathogenic and one mutation not described above [c.937T>C (p.Tyr313His)] were identified in the GBA gene, four patients were homozygotes and 22 compound heterozygotes. Twenty-four patients were diagnosed in non-neuropathic form (type 1) and two cases presented neurological involvement (type 2 or 3). The most common variant was c.1226A>G (p.Asn409Ser), which was detected in 24 patients, followed by c.1448T>C (p.Leu483Pro) variant, identified in 13 patients. The c.1448T>C (p.Leu483Pro) mutation has been presented in the most severe phenotypes with neurological involvement associated with type 2 and 3 GD, while c.1226A>G (p.Asn409Ser) mutation has not been associated with neurological alterations. Splenomegaly and bone disease were the most frequent clinical manifestations, and thrombocytopenia was the most common hematological disorder. Conclusions The c.1226A>G (p.Asn409Ser) and c.1448T>C (p.Leu483Pro) mutations were the most common. The c.937T>C (p.Tyr313His) was identified as a novel mutation. The c.1448T>C (p.Leu483Pro) mutation was associated with neurological alterations and c.1226A>G (p.Asn409Ser) mutation has not been associated it.

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

BACKGROUND

Gaucher disease is a rare multi-systemic metabolic disorder resulting from the deficiency of acid β-glucosidase activity, with consequent accumulation of glucocerebroside. Less than 15% of mean normal acid β-glucosidase activity in leukocytes is the gold standard for the diagnosis of Gaucher disease, and is generally supplemented by a massive elevation in chitotriosidase activity. We report here our experience in the biochemical diagnosis of Gaucher disease by showing the heterogeneity of the activity of enzymes over 25 years from 1993-2017, through the analysis of 5128 clinically suspected Gaucher disease cases referred to the Biochemical Genetics Department, National Research Centre, as the main reference lab in Egypt for the diagnosis of Inherited Metabolic Disorders.

METHODS

Acid β-glucosidase and chitotriosidase activities were measured in all referred cases. Sphinogmylinase activity was estimated for all cases with normal β-glucosidase activity and moderate elevation of chitotriosidase.

RESULTS

Out of the 5128 suspected cases, 882 (17%) showed a deficiency in acid β-glucosidase activity, accompanied by a raised chitotriosidase activity, ranges (213-66700 umol/l/h) and mean (7255 umol/l/h). Deficient chitotriosidase activity was found in 9 patients (1%) with low β-glucosidase. 451 cases were diagnosed with acid sphingomyelinase deficiency patients (8.8%).

CONCLUSION

Other biochemical markers are needed in addition to chitotriosidase for the diagnosis and follow up. Molecular testing was done to a relatively small number but needs to be done to all diagnosed patients as many mutations are known to predict the course of the disease.