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Introduction: Lysosomal storage disorders (LSD) are inherited diseases caused, in the majority of them, by the deficiency of lysosomal enzymatic activities. Ob-jectives: We aimed to analyze the usefulness of DBS samples for diagnosis of 4 LSDs, with the availability of a large quantity of patient samples. Design and methods: Blood samples from previously diagnosed patients with Fabry, Gaucher, Hunter, and Maro-teaux-Lamy syndromes and normal control individ-uals, were collected and dispen-sed in filter paper, and used for enzymatic activity determination. Results: Diagnosis of hemi/homo-zygous patients with Fabry, Hunter and Maroteaux-Lamy diseases using DBS samples showed ideal parameters of 100% sensitivity and specificity. DBS assay for Gaucher disease would need a posterior confirmatory step. Conclusions: Leukocyte measu-rement is the only reliable way to diagnose Gaucher disease. For Hunter, Fabry and Maroteaux-Lamy disorders discrimination between patients and controls seems adequate by DBS

FD was identified in 1 patient (.3%) in this first Latin American study. The patient presented with a late-onset oligo-symptomatic form of the disease. A large number of nonpathogenic mutations were present in our cohort, and it is essential that they not be mistaken for pathogenic mutations to avoid unnecessary enzyme replacement treatment.

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Gaucher disease (GD) is caused by mutations on the gene encoding for the lysosomal enzyme glucocerebrosidase. Type I GD (GD1) patients present anemia, hepatosplenomegaly and bone alterations. In spite of treatment, bone alterations in GD patients persist, including poor bone mineral density (BMD). Mechanisms leading to bone damage are not completely understood, but previous reports suggest that osteoclasts are involved. Chitotriosidase (CHIT) is the most reliable biomarker used in the follow up of patients, although its correlation with bone status is unknown. The aim of this work was to study the pro-osteoclastogenic potential in patients and to evaluate its correlation with CHIT activity levels and clinical parameters. PBMCs from treated patients and healthy controls were cultured in the presence of M-CSF, and mature osteoclasts were counted. BMD, blood CHIT activity and serum levels of CTX, BAP, and cytokines were evaluated in patients. We found that blood CHIT activity and osteoclast differentiation were significantly increased in patients, but no correlation between them was observed. Interestingly, osteoclast numbers but not CHIT, presented a negative correlation with BMD expressed as Z-score. CTX, BAP and serum cytokines involved in bone remodeling were found altered in GD1 patients. These results show for the first time a correlation between osteoclast differentiation and BMD in GD1 patients, supporting the involvement of osteoclasts in the bone pathology of GD1. Our results also suggest that an altered immune response may play an important role in bone damage.

The lysosomal storage disorder Fabry disease (FD) is caused by pathogenic mutations in the α-galactosidase A gene, localized in X chromosome. Deficient enzymatic activity of the product of this gene, the lysosomal hydrolase α-galactosidase A, leads to accumulation of its substrate globotriaosylceramide. Diagnosis of FD starts with clinical suspicion followed by confirmatory laboratory testing. The aim of this work is to report the 14 years’ experience and learnings in the diagnosis of patients with Fabry disease in Argentina from a specialized lysosomal diseases diagnosis laboratory and to report the genotype characterization of the 25 families from Argentina with FD detected by us.