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Chitinases and chitinase-like proteins are thought to play a role in innate inflammatory responses. Our study aimed to assess whether chitinase concentration and activity in induced sputum (IS) of patients exposed to tobacco smoke are related to the level of airway inflammation including the level and activity of chitinases and chitinase-like proteins. The study included 22 patients with chronic obstructive pulmonary disease (COPD), 12 non-COPD smokers, and nine nonsmoking subjects. Sputum CHIT1 and YKL-40 levels and chitinolytic activity were compared with sputum IL-6, IL-8, IL-18, and MMP-9 levels. A hierarchical cluster analysis was also performed. Sputum YKL-40 was higher in COPD patients than in the control groups. Sputum CHIT1 and YKL-40 levels correlated with IS inflammatory cell count as well as with MMP-9 and IL-8 levels. Two main clusters were revealed: Cluster 1 had lower chitinase levels and activity, lower IS macrophage and neutrophil count, and lower IS IL-8, IL-18, and MMP-9 than Cluster 2. Comparison of COPD patients from both clusters revealed significant differences in the IS inflammatory profile despite comparable clinical and functional data. Our findings seem to confirm the involvement of chitinases in smoking-associated chronic airway inflammation and show that airway chitinases may be a potential novel marker in COPD phenotyping.

Chitinases, enzymes that cleave chitin’s chain to low molecular weight chitooligomers, are widely distributed in nature. Mammalian chitinases belong to the 18-glycosyl-hydrolase family and can be divided into two groups: true chitinases with enzymatic activity (AMCase and chitotriosidase) and chitinase-like proteins (CLPs) molecules which can bind to chitin or chitooligosaccharides but lack enzymatic activity (eg, YKL-40). Chitinases are thought to be part of an innate immunity against chitin-containing parasites and fungal infections. Both groups of these hydrolases are lately evaluated also as chemical mediators or biomarkers involved in airway inflammation and fibrosis. The aim of this article is to present the current knowledge on the potential role of human chitinases and CLPs in the pathogenesis, diagnosis, and course of obstructive lung diseases. We also assessed the potential role of chitinase and CLPs inhibitors as therapeutic targets in chronic obstructive pulmonary disease and asthma.

Natalia Przysucha, Katarzyna Górska, Rafal Krenke Department of Internal Medicine, Pulmonary Diseases and Allergy, Medical University of Warsaw, Warsaw, PolandCorrespondence: Katarzyna GórskaDepartment of Internal Medicine, Pulmonary Diseases and Allergy, Medical University of Warsaw, Banacha 1A, Warsaw 02-097 Email drkpgorska@gmail.comAbstract: Chitinases, enzymes that cleave chitin’s chain to low molecular weight chitooligomers, are widely distributed in nature. Mammalian chitinases belong to the 18-glycosyl-hydrolase family and can be divided into two groups: true chitinases with enzymatic activity (AMCase and chitotriosidase) and chitinase-like proteins (CLPs) molecules which can bind to chitin or chitooligosaccharides but lack enzymatic activity (eg, YKL-40). Chitinases are thought to be part of an innate immunity against chitin-containing parasites and fungal infections. Both groups of these hydrolases are lately evaluated also as chemical mediators or biomarkers involved in airway inflammation and fibrosis. The aim of this article is to present the current knowledge on the potential role of human chitinases and CLPs in the pathogenesis, diagnosis, and course of obstructive lung diseases. We also assessed the potential role of chitinase and CLPs inhibitors as therapeutic targets in chronic obstructive pulmonary disease and asthma.Keywords: asthma, COPD, YKL-40, CHIT1, chitotriosidase, AMCase

Chitin (N-acetyl-glucosamine) is a highly abundant polysaccharide in nature and a major component of fungal cell walls, insects and common house dust allergens. Chitin also serves as microbe-associated molecular patterns (MAMPs) which is recognized by pattern recognition receptors (PRRs) of the innate immune system. In our previous study, we demonstrated that chitin oligomers longer than 6 units induce an inflammatory response via the PRR Toll-like receptor (TLR) 2. However, it remained unclear whether the co-receptors and accessory proteins are required for sensing and how chitin oligomers could be released from organisms containing polymeric chitin, which is considered immunologically inert. Interestingly, mammals express chitotriosidase-1 (CHIT1), namely chitinase, which has been determined as a biomarker constitutively expressed in fungal infection, cystic fibrosis and allergic asthma. However, the detailed role of CHIT1 in mediating innate immunity that correlates with its chitinolytic function has not been well understood. Thus, with this knowledge, it was hypothesized that host-chitinases like CHIT1 mediate the degradation of chitin-rich organisms to generate immunogenic oligomeric chitin, whose recognition is mediated by TLR2-expressing innate immune cells. Firstly, by examining two human chitotriosidase isoforms of 50 kDa and 39 kDa, we found that CHIT1 39 kDa isoform degradation products of chitin flakes, Candida albicans and house dust mites could induce TLR2-dependent NF-kB activation. Importantly, this immunogenic effect of CHIT1 39 kDa isoform required its intact catalytic activity. Furthermore, we found that chitin sensing of chitin particles and chitin-rich organisms might not be strictly dependent on direct contact, but could be mediated by diffusible oligomers generated in the presence of CHIT1. In addition, by using size exclusion chromatography (SEC) and mass spectrometric (MS) to prepare defined units of chitin oligomers, we found that optimally 14 - 16 units long oligomers triggered TLR2-NF- kB dependent inflammatory responses. To elucidate the involvement of TLR2 co- receptors, analysis in bimolecular complementary fluorescence (BiFC) assays and Tlr- deficient murine macrophages were performed and showed that chitin oligomers induce TLR1 and TLR2 heterodimerization to trigger NF-kB signaling and subsequently the production of pro-inflammatory cytokines. Finally, we demonstrated that CD14 and lipopolysaccharide binding protein (LBP), known mediators in the sensing of other hydrophobic MAMPs, enhanced and facilitated TLR2-NF-kB dependent chitin sensing. In overall, our study not only highlights CHIT1 as a novel therapeutic target for chitin- related inflammation disease but reveals an intricate system of MAMP generation, PRR sensing and induction of an enzymatic MAMP “generase” that bears resemblance to MAMP sensing in invertebrates.

BackgroundAlthough chitin is absent in humans, chitinases are present in healthy subjects and show dysregulated expression in a variety of diseases resulting from abnormal tissue injury and repair responses. It was shown that chitotriosidase (chitinase 1/CHIT1) and structurally-related chitinase 3-like 1 protein (CHI3L1/YKL-40) play important roles in the pathobiology of idiopathic pulmonary fibrosis (IPF), however little is known about their longitudinal serum levels and relationship to clinical measures in IPF.MethodsThe present study is the first to evaluate serial measurements of serum CHIT1 activity and YKL-40 concentrations in patients with IPF starting antifibrotic treatment and followed up for 24 months. In addition, baseline serum CHIT1 and YKL-40 were compared between patients with IPF and control subjects, and possible CHIT1 and YKL-40 relationships to longitudinal clinical assessments in IPF were explored.ResultsBaseline serum CHIT1 activity and YKL-40 concentrations were significantly elevated in patients with IPF compared to control subjects and showed similar discriminatory ability in distinguishing IPF from controls. No significant differences between the median serum CHIT1 activity and YKL-40 concentration measured over a study follow-up were noted. We found significantly elevated baseline serum CHIT1 activity in the progressors compared with the stables in the first year, while significantly increased baseline serum CHIT1 activity was noted in the stables compared to the progressors in the second year. Additionally, we observed a significant negative correlation between a change in serum YKL-40 concentration and a change in forced vital capacity (FVC) % predicted (% pred.) in the stables subgroup, whereas, a change in serum CHIT1 activity correlated negatively with a change in FVC% pred. in the progressors subgroup.ConclusionsThis explorative study findings add further evidence that CHIT1 and YKL-40 are upregulated in patients with IPF, and suggest that longitudinally stable serum CHIT1 activity and YKL-40 concentration levels may potentially be associated with the antifibrotic treatment response. In addition, our findings are supporting the possible role of CHIT1 and YKL-40 as candidate diagnostic and prognostic biomarkers in IPF. Further research is needed to validate present study findings.

Sebastian Majewski,1 Damian Tworek,2 Karolina Szewczyk,1 Justyna Kiszałkiewicz,3 Zofia Kurmanowska,1 Ewa Brzeziańska-Lasota,3 Hanna Jerczyńska,4 Adam Antczak,2 Wojciech Jerzy Piotrowski,1 Paweł Górski11Department of Pneumology and Allergy, Medical University of Lodz, Lodz, Poland; 2Department of General and Oncological Pulmonology, Medical University of Lodz, Lodz, Poland; 3Department of Molecular Bases of Medicine, Medical University of Lodz, Lodz, Poland; 4Central Scientific Laboratory (CoreLab), Medical University of Lodz, Lodz, PolandBackground: Despite the absence of endogenous chitin in humans, chitinases are present in the serum of healthy subjects and their levels are increased in a variety of chronic inflammatory conditions. It has been shown that chitotriosidase and structurally related chitinase-like protein-YKL-40 contribute to the pathogenesis of COPD. However, details regarding the relation of their systemic and local airways levels remain unknown.Objectives: To examine peripheral blood and sputum chitotriosidase and YKL-40 expression in smokers and patients with COPD.Methods: Forty patients with COPD, 20 healthy smokers and 10 healthy never-smokers were studied. Serum and induced sputum chitotriosidase protein and activity levels, YKL-40 concentrations, and their gene expression in sputum cells and peripheral blood mononuclear cells (PBMC) were evaluated.Results: Both chitotriosidase protein levels and activity were higher in sputum obtained from COPD subjects compared to healthy never-smokers (P

Sebastian Majewski,1 Damian Tworek,2 Karolina Szewczyk,1 Justyna Kiszałkiewicz,3 Zofia Kurmanowska,1 Ewa Brzeziańska-Lasota,3 Hanna Jerczyńska,4 Adam Antczak,2 Wojciech Jerzy Piotrowski,1 Paweł Górski11Department of Pneumology and Allergy, Medical University of Lodz, Lodz, Poland; 2Department of General and Oncological Pulmonology, Medical University of Lodz, Lodz, Poland; 3Department of Molecular Bases of Medicine, Medical University of Lodz, Lodz, Poland; 4Central Scientific Laboratory (CoreLab), Medical University of Lodz, Lodz, PolandBackground: Despite the absence of endogenous chitin in humans, chitinases are present in the serum of healthy subjects and their levels are increased in a variety of chronic inflammatory conditions. It has been shown that chitotriosidase and structurally related chitinase-like protein-YKL-40 contribute to the pathogenesis of COPD. However, details regarding the relation of their systemic and local airways levels remain unknown.Objectives: To examine peripheral blood and sputum chitotriosidase and YKL-40 expression in smokers and patients with COPD.Methods: Forty patients with COPD, 20 healthy smokers and 10 healthy never-smokers were studied. Serum and induced sputum chitotriosidase protein and activity levels, YKL-40 concentrations, and their gene expression in sputum cells and peripheral blood mononuclear cells (PBMC) were evaluated.Results: Both chitotriosidase protein levels and activity were higher in sputum obtained from COPD subjects compared to healthy never-smokers (P

// Fei-Feng Li 1, 2, * , Peng Yan 3, * , Zhi-Xun Zhao 3 , Zheng Liu 4 , Da-Wei Song 3 , Xing-Wang Zhao 3 , Xi-Shan Wang 2, 4 , Gui-Yu Wang 2, 3 , Shu-Lin Liu 1, 2, 5 1 Genomics Research Center, State-Province Key Laboratory of Biopharmaceutical Engineering, Harbin Medical University, Harbin, China 2 Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Heilongjiang, China 3 Department of Colorectal Surgery, Second Affiliated Hospital of Harbin Medical University, Harbin, China 4 Department of Colorectal Surgery, Cancer Institute and Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China 5 Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Canada * These authors are contributed equally to this work Correspondence to: Shu-Lin Liu, email: slliu@ucalgary.ca Gui-Yu Wang, email: guiywang@gmail.com Xi-Shan Wang, email: wxshan1208@126.com Keywords: colorectal cancer, CHIT1, C-reaction protein, gene expression, microbe Received: January 10, 2016 Accepted: April 16, 2016 Published: May 02, 2016 ABSTRACT Colorectal cancer (CRC) is one of the most common solid tumors worldwide, often associated with inflammation. The microbes in the human intestine have a key role in inflammations and CRC. Chitotriose renders growth advantage to some bacteria, especially some pathogens, and thus has a role in inflammations. The enzyme chitotriosidase, encoded by the CHIT1 gene of the host, may degrade chitotriose with different efficiencies depending on the alleles. We sequenced the CHIT1 gene for 320 Chinese Han CRC patients and 404 normal controls, and focused on variations rs61745299 and rs35920428 within the CHIT1 gene for their possible roles in CRC. Statistical analyses were conducted using Chi-Square Tests as implemented in SPSS (version 19.0). Multiple sequence alignment was conducted using the Vector NTI, and protein expression levels were analyzed by western blotting. The two variations, rs61745299 and rs35920428 within the CDS region of CHIT1 gene, were associated with the risk of CRC (both with P values < 0.001). Western blotting analysis showed that the variations increased the expression levels of the CHIT1 and C-reaction protein genes in the cancer tissue. We conclude that the two variations of CHIT1 , rs61745299 and rs35920428, increase expression of the gene and are associated with CRC in Chinese Han populations.

ObjectiveTo investigate the role of neuroinflammation in asymptomatic and symptomatic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) mutation carriers.MethodsThe neuroinflammatory markers chitotriosidase 1 (CHIT1), YKL-40 and glial fibrillary acidic protein (GFAP) were measured in cerebrospinal fluid (CSF) and blood samples from asymptomatic and symptomatic ALS/FTD mutation carriers, sporadic cases and controls by ELISA.ResultsCSF levels of CHIT1, YKL-40 and GFAP were unaffected in asymptomatic mutation carriers (n=16). CHIT1 and YKL-40 were increased in gALS (pConclusionOur data indicate that neuroinflammation is linked to the symptomatic phase of ALS/FTD and shows a similar pattern in sporadic and genetic cases. ALS and FTD are characterised by a different neuroinflammatory profile, which might be one driver of the diverse presentations of the ALS/FTD syndrome.

Lymphatic filariasis, caused by lymphatic filarial parasites, Wuchereria bancrofti, and Brugia malayi, causes significant morbidity and disability to 120 million people in the tropics and subtropics. Chitin has an important role for embryogenesis in adult worms and is a component of microfilaria sheath. Human chitotriosidase (CHIT1) is a chitin-degrading enzyme which provides a protective role against chitin-containing pathogens. Here, we determined the association of CHIT1 polymorphisms with susceptibility to bancroftian filariasis (BF) in 88 individuals at the Thai&ndash, Myanmar border. Two common polymorphisms of CHIT1, contributing inactive CHIT protein, including 24 base pair (24 bp) duplication in exon 10, and p. G102S in exon 4 were genotyped by allele-specific Polymerase Chain Reaction (PCR) and PCR sequencing, respectively. Unexpectedly, genotype frequencies of 24 bp duplication insertion homozygous (INS/INS) were significantly higher in endemic normal (EN) (40.0%) than BF patients (31.4%). In contrast, genotype frequencies of p. G102S homozygous (A/A) in BF patients (21.6%) was higher than in EN (19.0%) without statistical difference. Mutant allele frequencies of 24 bp duplication were 0.6125 (98/160) and p. G102S were 0.392 (69/176). Genotype and allele frequencies of CHIT1, 24 bp duplication, and p. G102S, showed no association with BF patients.

Osteolytic bone disease is a common manifestation of multiple myeloma (MM) that leads to progressive skeleton destruction and is the most severe cause of morbidity in MM patients. It results from increased osteolytic activity and decrease osteoblastic function. Activation of mammalian chitinases chitotriosidase (CHIT1) and YKL40 is associated with osteoclast (OCs) differentiation and bone digestion. In the current study, we investigated the effect of two Bortezomib's concentration (2.5 and 5 nM) on osteoclastogenesis by analyzing regulation of chitinase expression. OCs exposition to bortezomib (BO) was able to inhibit the expression of different OCs markers such as RANK, CTSK, TRAP, and MMP9. In addition BO-treatment reduced CHIT1 enzymatic activity and both CHIT1 and YKL40 mRNA expression levels and cytoplasmatic and secreted protein. Moreover, immunofluorescence evaluation of mature OCs showed that BO was able to translocate YKL40 into the nucleus, while CHIT1 remained into the cytoplasm. Since MM cell lines such as U266, SKM-M1 and MM1 showed high levels of CHIT1 activity, we analyzed bone resorption ability of U266 using dentin disk assay resorption pits. Silencing chitinase proteins in U266 cell line with specific small interfering RNA, resulted in pits number reduction on dentine disks. In conclusion, we showed that BO decreases osteoclastogenesis and reduces bone resorption in OCs and U266 cell line by modulating the chitinases CHIT1 and YKL40. These results indicate that chitinases may be a therapeutic target for bone disease in MM patients.

Chitin, after cellulose, the second most abundant biopolymer on earth, is a key component of insects, fungi, and house-dust mites. Lower life forms are endowed with chitinases to defend themselves against chitin-bearing pathogens. Unexpectedly, humans were also found to express chitinases as well as chitinase-like proteins that modulate immune responses. Particularly, increased levels of the chitinase-like protein YKL-40 have been associated with severe asthma, cystic fibrosis, and other inflammatory disease conditions. Here, we summarize and discuss the potential role of chitin, chitinases, and chitinase-like proteins in pediatric lung diseases.

Osteoarthritis is a degenerative joint disease, which affects millions of people around the world. It occurs when the protective cartilage at the end of bones wears over time, leading to loss of flexibility of the joint, pain and stiffness. The cause of osteoarthritis is unknown, but its development is associated with different factors, such as metabolic, genetic, mechanical and inflammatory ones. In recent years the biological role of chitinases has been studied in relation to different inflammatory diseases and more in particular the elevated levels of human cartilage glycoprotein 39 (CHI3L1) and chitotriosidase (CHIT1) have been reported in a variety of diseases including chronic inflammation and degenerative disorders. The aim of this study was to investigate, by immunohistochemistry, the distribution of CHI3L1 and CHIT1 in osteoarthritic and normal rat articular cartilage, to discover their potential role in the development of this disease. The hypothesis was that the expression of chitinases could increase in OA disease. Immunohistochemical analysis showed that CHI3L1 and CHIT1 staining was very strong in osteoarthritic cartilage, especially in the superficial areas of the cartilage most exposed to mechanical load, while it was weak or absent in normal cartilage. These findings suggest that these two chitinases could be functionally associated with the development of osteoarthritis and could be used as markers, so in the future they could have a role in the daily clinical practice to stage the severity of the disease. However, the longer-term in vivo and in vitro studies are needed to understand the exact mechanism of these molecules, their receptors and activities on cartilage tissue.

AD e DR: bolseiros FCT. Chitotriosidase is an enzyme secreted by activated macrophages and a useful biomarker in several lysosomal and nonlysosomal diseases. However, chitotriosidase gene (CHIT1) mutations may lead to inaccuracy in the significance of this biomarker. Reports on the molecular spectrum of genetic variation in chitotriosidase are rare, and this is one of the few that focus on a specific population group. In this work we assessed the variation of CHIT1 mutations in ten normal controls and detected six missense alterations. G102S, a polymorphism with known altered catalytic properties, was the most frequent being detected in 4/10 individuals. Using allelic discrimination we tested 503 individuals, randomly sampled from the Portuguese population. Variant G102S was detected in 49.5% of the individuals and presented an allele frequency of 0.29. The results of this study showed that variability in CHIT1 gene is considerable and that G102S polymorphism presents a high frequency in the Portuguese. Financed by national funds through the FCT/MCTES. Project PIC/IC/82822/2007 (2009).

Chitotriosidase (EC.3.2.1.14) is an enzyme secreted by activated macrophages. This chitinase is useful as a biochemical marker in several lysosomal and nonlysosomal diseases due to its increased activity in such conditions (MIM#600031. CHIT1 variants may account for additional biochemical variability and should be considered when using chitotriosidase activity as a secondary evaluation marker in diagnosis and disease prognosis. This work was financially supported by National Funds through FCT (MCTES) under Project PIC/IC/82822/2007. AJD and DR have FCT grants.

AJD and DR are both recipients of FCT grants. 18th ESGLD Meeting: abstrats. European Study Group on Lysosomal Diseases, p. 56 Chitotriosidase (EC.3.2.1.14) is an enzyme secreted by activated macrophages. This chitinase is useful as a biochemical marker in several lysosomal and nonlysosomal diseases due to its increased activity in such conditions (MIM#600031). In Gaucher Disease type 1 (GD, MIM#230800) patients, the chitotriosidase activity is increased in about 600-fold compared with normal controls. Chitotriosidase is not only useful as a disease severity marker but also measures the effectiveness of the therapy in GD. However, chitotriosidase gene (CHIT1, 1q31-q32) mutations modify the plasma chitotriosidase levels and therefore introduce a degree of variability that can be misleading. The most well known cause of chitotriosidase deficiency is the common 24 bp duplication. Nonetheless, other mutations that occur in this gene also lead to altered catalytic properties. However, as suggested by Bussink and collaborators, slight modifications in assay conditions may help avoiding such problems. In the present work we determined the frequency of two mutations which had appeared in a preliminary screening. This work was financially supported by National Funds through FCT - Fundação da Ciência e Tecnologia (MCTES – Portugal) under Project «PIC/IC/82822/2007».

Asthma is a disease characterized by chronic inflammation of the airway, thought to result from inappropriate activation of the Th2 immune response. Recent work has shown that chitinase proteins are strongly upregulated during Th2 inflammation in the lungs of mice. Studies in mouse models have implicated chitinase activity in both promotion of Th2 inflammation and protection from the Th2-priming effects of chitin in the lungs. Herein we detail investigation of chitinases in human asthma. Namely, we explored the possibility that variants affecting the enzymatic activity of the two active chitinase proteins, acidic mammalian chitinase (AMCase) and chitotriosidase (CHIT1), may alter risk for human asthma. Secondly, we have determined expression and activity of these enzymes in lungs of healthy and asthmatic subjects. We identified a coding haplotype in the AMCase gene strongly associated with protection from asthma among African American asthma case-control groups. This association was also observed in family-based analysis of a group of Latino American asthmatic trios. Through recombinant protein expression and biochemical characterization we have found the protective AMCase isoform to be considerably more active at pH values corresponding to the lung, stomach, and lysosomes. In contrast, no association was observed with a common null genetic variant in the CHIT1 gene in either African Americans, or Latinos. We found CHIT1 to be responsible for the majority of chitinase activity in the human lung based on pH profile of enzymatic activity and genetic analysis of a CHIT1 null variant. Median chitinase activity in BAL tended to be lower than normal in asthma. AMCase protein was detectable in the lung, but mRNA transcripts expressed from lung tissues was consistent with an isoform lacking enzymatic activity. AMCase protein expression was observed to be lower in the BAL of asthmatics. This work is the first evidence that functional genetic variants in chitinase genes are associated with risk for asthma, and are consistent with possible Th2-priming effects of environmental chitin. Additionally, we find differential expression of the two active chitinases in the human lung and reveal differences in chitinase protein expression and enzymatic activity in lung disease.

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International audience; A 24 bp duplication in the CHIT1 gene (H allele) is associated with a deficiency in the activity of chitotriosidase, an enzyme with the capability to hydrolyse chitin. A recent study in European and two sub-Saharan populations suggested a relationship between the presence of the mutation, improved environmental conditions, and the disappearance of parasitic diseases, including Plasmodium falciparum malaria. This result was not supported by the high frequency of the 24 bp duplication in a sample from Taiwan, an area with high malaria endemicity until 40 years ago. In this study, we analysed the frequency variability of the H allele in Mediterranean populations and its internal variability in Sardinia (Italy) with respect to malaria, which had been endemic on the island until its eradication during 1946-1950. The pattern of H frequency distributions is not consistent with the hypothesis of selective pressures acting on CHIT1 gene. The Moran's index coefficient and correlogram seem to indicate, indeed, that allele distribution was determined by random factors. The pattern of frequency distribution suggests a possible Asiatic origin of the H allele, but it could be possible also that the mutant allele had diffused out of Africa, and was subsequently lost from African populations.

Chitotriosidase is a human chitinase produced by macrophages. Its enzymatic activity is markedly elevated in serum of patients suffering from lysosomal storage disorders, as well as other diseases in which macrophages are activated. Therefore, it is a useful tool as a secondary marker in the diagnosis of several disorders including Gaucher disease type 1 and Niemann–Pick disease. The determination of chitotriosidase levels as a diagnosis complement in some lysosomal storage disorders and in enzyme replacement therapy follow-up of Gaucher disease patients is of great importance. However, the fact that a mutation caused by a 24-bp duplication in the CHIT1 gene resulting in deficiency of plasma chitotriosidase activity is very frequent makes the establishment of the frequency of this mutation in different population groups necessary. Furthermore, in order to validate the use of chitotriosidase activity as a marker, it is indispensable to screen individuals for this particular mutation. In this work, we present the results of a study where the allelic frequency of the abovementioned CHIT1 gene mutation was determined in the Portuguese population by real-time PCR. The frequency of carriers encountered in this sample of Portuguese individuals was of 37%.