Prevalence of lysosomal storage diseases in Portugal

Chromatographic pattern classification

In this paper, we propose and evaluate methodologies for the classification of images from thin-layer chromatography. Each individual sample is characterized by an intensity profile that is further represented into a feature space. The first steps of this process aim at obtaining a robust estimate of the intensity profile by filtering noise, reducing the influence of background changes, and by fitting a mixture of Gaussians. The resulting profiles are represented by a set of appropriate features trying to characterize the state of nature, here spread out over four classes, one for normal subjects and the other three corresponding to lysosomal diseases, which are disorders responsible for severe nerve degeneration. For classification purposes, a novel solution based on a hierarchical structure is proposed. The main conclusion of this paper is that an automatically generated decision tree presents better results than more conventional solutions, being able to deal with the natural imbalance of the data that, as consequence of the rarity of lysosomal disorders, has very few representative cases in the disease classes when compared with the normal population.

A prospective, cross-sectional survey study of the natural history of Niemann-Pick disease type B

OBJECTIVE

The objective of this study was to characterize the clinical features of patients with Niemann-Pick disease type B and to identify efficacy end points for future clinical trials of enzyme-replacement therapy.

METHODS

Fifty-nine patients who had Niemann-Pick disease type B, were at least 6 years of age, and manifested at least 2 disease symptoms participated in this multicenter, multinational, cross-sectional survey study. Medical histories; physical examinations; assessments of cardiorespiratory function, clinical laboratory data, and liver and spleen volumes; radiographic evaluation of the lungs and bone age; and quality-of-life assessments were obtained during a 2- to 3-day period.

RESULTS

Fifty-three percent of the patients were male, 92% were white, and the median age was 17.6 years. The R608del mutation accounted for 25% of all disease alleles. Most patients initially presented with splenomegaly (78%) or hepatomegaly (73%). Frequent symptoms included bleeding (49%), pulmonary infections and shortness of breath (42% each), and joint/limb pain (39%). Growth was markedly delayed during adolescence. Patients commonly had low levels of platelets and high-density lipoprotein, elevated levels of low-density lipoprotein, very-low-density lipoprotein, triglycerides, leukocyte sphingomyelin, and serum chitotriosidase, and abnormal liver function test results. Nearly all patients had documented splenomegaly and hepatomegaly and interstitial lung disease. Patients commonly showed restrictive lung disease physiology with impaired pulmonary gas exchange and decreased maximal exercise tolerance. Quality of life was only mildly decreased by standardized questionnaires. The degree of splenomegaly correlated with most aspects of disease, including hepatomegaly, growth, lipid profile, hematologic parameters, and pulmonary function.

CONCLUSIONS

This study documents the multisystem involvement and clinical variability of Niemann-Pick B disease. Several efficacy end points were identified for future clinical treatment studies. Because of its correlation with disease severity, spleen volume may be a useful surrogate end point in treatment trials, whereas biomarkers such as chitotriosidase also may play a role in monitoring patient treatment responses.

A nonsense mutation in the LIMP-2 gene associated with progressive myoclonic epilepsy and nephrotic syndrome

The main clinical features of two siblings from a consanguineous marriage were progressive myoclonic epilepsy without intellectual impairment and a nephrotic syndrome with a strong accumulation of C1q in capillary loops and mesangium of kidney. The biochemical analysis of one of the patients revealed a normal beta-glucocerebrosidase activity in leukocytes, but a severe enzymatic deficiency in cultured skin fibroblasts. This deficiency suggested a defect in the intracellular sorting pathway of this enzyme. The sequence analysis of the gene encoding LIMP-2 (SCARB2), the sorting receptor for beta-glucocerebrosidase, confirmed this hypothesis. A homozygous nonsense mutation in codon 178 of SCARB2 was found in the patient, whereas her healthy parents were heterozygous for the mutation. Besides lacking immunodetectable LIMP-2, patient fibroblasts also had decreased amounts of beta-glucocerebrosidase, which was mainly located in the endoplasmic reticulum, as assessed by its sensitivity to Endo H. This is the first report of a mutation in the SCARB2 gene associated with a human disease, which, contrary to earlier proposals, shares no features with Charcot-Marie-Tooth disease both at the clinical and neurophysiological levels.

Early detection of Pompe disease by newborn screening is feasible: results from the Taiwan screening program

OBJECTIVE

Pompe disease is an autosomal recessive lysosomal storage disorder that is caused by deficient acid alpha-glucosidase activity and results in progressive, debilitating, and often life-threatening symptoms involving the musculoskeletal, respiratory, and cardiac systems. Recently, enzyme replacement therapy with alglucosidase alpha has become possible, but the best outcomes in motor function have been achieved when treatment was initiated early. The aim of this study was to test the feasibility of screening newborns in Taiwan for Pompe disease by using a fluorometric enzymatic assay to determine acid alpha-glucosidase activity in dried blood spots.

METHODS

We conducted a large-scale newborn screening pilot program between October 2005 and March 2007. The screening involved measuring acid alpha-glucosidase activity in dried blood spots of approximately 45% of newborns in Taiwan. The unscreened population was monitored as a control.

RESULTS

Of the 132 538 newborns screened, 1093 (0.82%) repeat dried blood-spot samples were requested and retested, and 121 (0.091%) newborns were recalled for additional evaluation. Pompe disease was confirmed in 4 newborns. This number was similar to the number of infants who received a diagnosis of Pompe disease in the control group (n = 3); however, newborn screening resulted in an earlier diagnosis of Pompe disease: patients were <1 month old compared with 3 to 6 months old in the control group.

CONCLUSIONS

To our knowledge, this is the first large-scale study to show that newborn screening for Pompe disease is feasible. Newborn screening allows for earlier diagnosis of Pompe disease and, thus, for assessment of the value of an earlier start of treatment.

Management of non-neuronopathic Gaucher disease with special reference to pregnancy, splenectomy, bisphosphonate therapy, use of biomarkers and bone disease monitoring

Enzyme replacement was introduced as treatment for non-neuronopathic Gaucher disease more than 15 years ago. To ensure the best use of this costly ultra-orphan agent, a systematic disease management approach has been proposed by an international panel; this includes the development, by consensus, of achievable treatment goals. Here we critically review these goals and monitoring guidelines and incorporate emerging experience of the disease in the therapeutic era, as well as contemporary clinical research. This review makes recommendations related specifically to the management of pregnancy; the appropriate use of splenectomy and bisphosphonate treatment; the relevance of biochemical markers to disease monitoring; and the use of semi-quantitative methods for assessing bone marrow infiltration. In addition, we identify key areas for development, including the requirement for a validated index of disease severity; the need to correlate widely used biomarkers with long-term disease outcomes, and the desirability of establishing agreed standards for monitoring of bone disease particularly in infants and children with Gaucher disease.

Growth charts for patients affected with Morquio A disease

Children with Morquio A disease grow poorly and become physically handicapped because of systemic bone disease. The purpose of this study was to describe observed growth patterns and their relationship with the physical condition of patients with Morquio A. In a one-center study, questionnaire-based longitudinal and cross sectional data were used to develop growth curves, to assess physical activity and to determine the incidence of surgical procedures in 354 patients with Morquio A. Mean birth lengths of boys and girls were 52.6 and 52.1 cm, respectively. The mean final heights for males and females at 18 years and older were 122.4 +/- 21.5 and 113.1 +/- 22.6 cm, respectively. These results corresponded to -7.4 SD for males and -7.7 SD for females compared to the normal healthy controls. Mean birth weights for boys and girls were 3.59 +/- 0.58 and 3.5 +/- 0.7 kg, respectively. The mean body mass index for males and females at over 18 years of age was 24.7 +/- 6.1 and 25.6 +/- 5.4 kg/m(2), respectively. The growth pattern in Morquio A patients was characterized by impaired growth velocity after 1 year of age. This is the first report providing growth charts for patients with Morquio A, which can help with monitoring the disease and assessing the clinical efficacy of treatments.

Sanfilippo syndrome: a mini-review

Mucopolysaccharidosis type III (MPS III, Sanfilippo syndrome) is an autosomal recessive disorder, caused by a deficiency in one of the four enzymes involved in the lysosomal degradation of the glycosaminoglycan heparan sulfate. Based on the enzyme deficiency, four different subtypes, MPS IIIA, B, C, and D, are recognized. The genes encoding these four enzymes have been characterized and various mutations have been reported. The probable diagnosis of all MPS III subtypes is based on increased concentration of heparan sulfate in the urine. Enzymatic assays in leukocytes and/or fibroblasts confirm the diagnosis and allow for discrimination between the different subtypes of the disease. The clinical course of MPS III can be divided into three phases. In the first phase, which usually starts between 1 and 4 years of age, a developmental delay becomes apparent after an initial normal development during the first 1-2 years of life. The second phase generally starts around 3-4 years and is characterized by severe behavioural problems and progressive mental deterioration ultimately leading to severe dementia. In the third and final stage, behavioural problems slowly disappear, but motor retardation with swallowing difficulties and spasticity emerge. Patients usually die at the end of the second or beginning of the third decade of life, although survival into the fourth decade has been reported. Although currently no effective therapy is yet available for MPS III, several promising developments raise hope that therapeutic interventions, halting the devastating mental and behavioural deterioration, might be feasible in the near future.

Immune system irregularities in lysosomal storage disorders

Lysosomal storage disorders (LSDs) are genetically inherited diseases characterized by the accumulation of disease-specific biological materials such as proteolipids or metabolic intermediates within the lysosome. The lysosomal compartment's central importance to normal cellular function can be appreciated by examining the various pathologies that arise in LSDs. These disorders are invariably fatal, and many display profound neurological impairment that begins in childhood. However, recent studies have revealed that several LSDs also have irregularities in the function of the immune system. Gaucher disease, mucopolysaccharidosis VII, and alpha-mannosidosis are examples of a subset of LSD patients that are predisposed towards immune suppression. In contrast, GM2 gangliosidosis, globoid cell leukodystrophy, Niemann-Pick disease type C1 and juvenile neuronal ceroid lipofuscinosis are LSDs that are predisposed towards immune system hyperactivity. Antigen presentation and processing by dedicated antigen presenting cells (APCs), secretion of pore-forming perforins by cytotoxic-T lymphocytes, and release of pro-inflammatory mediators by mast cells are among the many crucial immune system functions in which the lysosome plays a central role. Although the relationship between the modification of the lysosomal compartment in LSDs and modulation of the immune system remains unknown, there is emerging evidence for early neuroimmune responses in a variety of LSDs. In this review we bridge biochemical studies on the lysosomal compartment's role in the immune system with clinical data on immune system irregularities in a subset of LSDs.

Clinical and genetic spectrum of Sanfilippo type C (MPS IIIC) disease in The Netherlands

Mucopolysaccharidosis IIIC (MPS IIIC, Sanfilippo C syndrome) is a lysosomal storage disorder caused by deficiency of the lysosomal enzyme acetyl-CoA:alpha-glucosaminide N-acetyltransferase (HGSNAT). We performed a clinical study on 29 Dutch MPS IIIC patients and determined causative mutations in the recently identified HGSNAT gene. Psychomotor development was reported to be normal in all patients during the first year of life. First clinical signs were usually noted between 1 and 6 years (mean 3.5 years), and consisted of delayed psychomotor development and behavioral problems. Other symptoms included sleeping and hearing problems, recurrent infections, diarrhoea and epilepsy. Two sisters had attenuated disease and did not have symptoms until the third decade. Mean age of death was 34 years (range 25-48). Molecular analysis revealed mutations in both alleles for all patients except one. Altogether 14 different mutations were found: two splice site mutations, one frame shift mutation due to an insertion, three nonsense mutations and eight missense mutations. Two mutations, p.R344C and p.S518F, were frequent among probands of Dutch origin representing 22.0% and 29.3%, respectively, of the mutant alleles. This study demonstrates that MPS IIIC has a milder course than previously reported and that both severity and clinical course are highly variable even between sibs, complicating prediction of the clinical phenotype for individual patients. A clear phenotype-genotype correlation could not be established, except that the mutations p.G262R and p.S539C were only found in two sisters with late-onset disease and presumably convey a mild phenotype.

Newborn screening for Pompe disease: synthesis of the evidence and development of screening recommendations

BACKGROUND

Pompe disease is a lysosomal storage disorder that leads to the accumulation of glycogen and subsequently to muscle weakness, organ damage, and death. Pompe disease is detectable through newborn screening, and treatment has become available recently.

OBJECTIVE

Our goal was to review systematically all available evidence regarding screening for infantile Pompe disease to help policy makers determine whether Pompe disease should be added to their state's newborn screening battery.

METHODS

We searched online databases, including Medline, clinicaltrials.gov, and the Computer Retrieval of Information on Scientific Projects database, as well as Web sites maintained by federal organizations (eg, the Food and Drug Administration) and other nonprofit or private organizations (eg, the March of Dimes and Genzyme Corp), by using the terms "glycogen storage disease type II," "Pompe disease," and "Pompe's disease." We also obtained preliminary findings from a screening program in Taiwan. Data were critically appraised and extracted by 2 investigators, one who is an expert in systematic review methods and the other who is an expert in Pompe disease.

RESULTS

The prevalence of Pompe disease has been estimated to be approximately 1 case per 40,000. Small studies suggest that enzyme therapy is highly efficacious in infantile Pompe disease and that earlier intervention leads to improved outcomes. Screening cannot distinguish between infantile and late-onset Pompe disease. The current screening program in Taiwan has a high false-positive rate; however, the threshold was purposely set low to ensure that no case would be missed.

CONCLUSIONS

Pilot studies of screening are needed to identify the most efficacious strategy for screening and determine how to manage cases of late-onset Pompe disease before screening for Pompe disease is adopted widely by newborn screening programs.

The pathogenesis and treatment of acid sphingomyelinase-deficient Niemann-Pick disease

Patients with types A and B Niemann-Pick disease (NPD) have an inherited deficiency of acid sphingomyelinase (ASM) activity. The clinical spectrum of this disorder ranges from the infantile, neurological form that results in death by 3 years of age (type A NPD) to the non-neurological form (type B NPD) that is compatible with survival into adulthood. Intermediate cases also have been reported, and the disease is best thought of as a single entity with a spectrum of phenotypes. ASM deficiency is panethnic, but appears to be more frequent in individuals of Middle Eastern and North African descent. Current estimates of the disease incidence range from approximately 0.5 to 1 per 100,000 births. However, these approximations likely under estimate the true frequency of the disorder since they are based solely on cases referred to biochemical testing laboratories for enzymatic confirmation. The gene encoding ASM (SMPD1) has been studied extensively; it resides within an imprinted region on chromosome 11, and is preferentially expressed from the maternal chromosome. Over 100 SMPD1 mutations causing ASM-deficient NPD have been described, and some useful genotype-phenotype correlations have been made. Based on these findings, DNA-based carrier screening has been implemented in the Ashkenazi Jewish community. ASM 'knockout' mouse models also have been constructed and used to investigate disease pathogenesis and treatment. Based on these studies in the mouse model, an enzyme replacement therapy clinical trial has recently begun in adult patients with non-neurological ASM-deficient NPD.

Mutational analysis of 105 mucopolysaccharidosis type VI patients

Mucopolysaccharidosis type VI (MPS VI; Maroteaux-Lamy syndrome) is a lysosomal storage disorder caused by mutations in the N-acetylgalactosamine-4-sulfatase (arylsulfatase B, ARSB) gene. ARSB is a lysosomal enzyme involved in the degradation of the glycosaminoglycans (GAG) dermatan and chondroitin sulfate. ARSB mutations reduce enzyme function and GAG degradation, causing lysosomal storage and urinary excretion of these partially degraded substrates. Disease onset and rate of progression is variable, producing a spectrum of clinical presentation. In this study, 105 MPS VI patients-representing about 10% of the world MPS VI population-were studied for molecular genetic and biochemical parameters. Direct sequencing of patient genomic DNA was used to identify ARSB mutations. In total, 83 different disease-causing mutations were found, 62 of which were previously unknown. The novel sequence changes included: 38 missense mutations, five nonsense mutations, 11 deletions, one insertion, seven splice-site mutations, and four polymorphisms. ARSB mutant protein and residual activity were determined on fibroblast extracts for each patient. The identification of many novel mutations unique to individuals/their families highlighted the genetic heterogeneity of the disorder and provided an appropriate cohort to study the MPS VI phenotypic spectrum. This mutation analysis has identified a clear correlation between genotype and urinary GAG that can be used to predict clinical outcome.

Management guidelines for mucopolysaccharidosis VI

Mucopolysaccharidosis VI (Maroteaux-Lamy syndrome) is a lysosomal storage disease that is characterized by systemic clinical manifestations and significant functional impairment. Diagnosis and management are often challenging because of the considerable variability in symptom presentation and rate of progression. The optimal standard of care should be based on evidence from randomized, controlled trials, meta-analyses, systematic reviews, and expert opinion. In support of this goal, comprehensive management guidelines have been drafted by an international group of experts in the management of patients with mucopolysaccharidosis VI. The guidelines provide a detailed outline of disease manifestations by body system, recommendations for regular assessments, and an overview of current treatment options.

Incidence rates of progressive childhood encephalopathy in Oslo, Norway: a population based study

Background

Progressive encephalopathy (PE) in children is a heterogeneous group of diseases mainly composed of metabolic diseases, but it consists also of neurodegenerative disorders where neither metabolic nor other causes are found. We wanted to estimate the incidence rate and aetiology of PE, as well as the age of onset of the disease.

Methods

We included PE cases born between 1985 and 2003, living in Oslo, and registered the number presenting annually between 1985 and 2004. Person-years at risk between 0 and 15 years were based on the number of live births during the observation period which was divided into four 5-year intervals. We calculated incidence rates according to age at onset which was classified as neonatal (0–4 weeks), infantile (1–12 months), late infantile (1–5 years), and juvenile (6–12 years).

Results

We found 84 PE cases representing 28 diagnoses among 1,305,997 person years, giving an incidence rate of 6.43 per 100,000 person years. The age-specific incidence rates per 100,000 were: 79.89 (<1 year), 8.64 (1–2 years), 1.90 (2–5 years), and 0.65 (>5 years). 66% (55/84) of the cases were metabolic, 32% (27/54) were neurodegenerative, and 2% (2/84) had HIV encephalopathy. 71% (60/84) of the cases presented at < 1 year, 24% (20/84) were late infantile presentations, and 5% (4/84) were juvenile presentations. Neonatal onset was more common in the metabolic (46%) (25/55) compared to the neurodegenerative group (7%) (2/27). 20% (17/84) of all cases were classified as unspecified neurodegenerative disease.

Conclusion

The overall incidence rate of PE was 6.43 per 100,000 person years. There was a strong reduction in incidence rates with increasing age. Two-thirds of the cases were metabolic, of which almost half presented in the neonatal period.

International Morquio A Registry: clinical manifestation and natural course of Morquio A disease

Mucopolysaccharidosis IVA (MPS IVA; Morquio A disease) is a lysosomal storage disorder caused by deficiency of N-acetylgalactosamine-6-sulfate sulfatase. The natural history of this disease is incompletely understood. To study which variables influence the clinical outcome, we conducted a study in which MPS IVA patients were asked to fill out a questionnaire with inquiries regarding family history, diagnosis, signs and symptoms, height, weight, surgical history, physical activity, and general complaints. A total of 326 patients (172 male, 154 female) from 42 countries enrolled in the Morquio A Registry programme. The mean age of patients enrolled was 14.9 years for males and 19.1 years for females, with a wide range of 1-73 years. Sixty-four per cent of the patients were under 18 years. Initial symptoms were recognized between 1 and 3 years of age (mean age 2.1 years) and mean age at diagnosis for the patients was 4.7 years. A progressive skeletal dysplasia was commonly observed among the MPS IVA patients. Fifty per cent of patients underwent surgical operations to improve their quality of life. The most frequent surgical sites include neck (51%), ear (33%), leg (26%) and hip (25%). The birth length for affected males and females was 52.2 +/- 4.7 cm and 52.2 +/- 4.5 cm, respectively. The final adult height for affected males and females was 122.5 +/- 22.5 cm and 116.5 +/- 20.5 cm, respectively. The results of this study provide a reference for assessment of efficacy for studies of novel therapies.

Molecular characterization of Portuguese patients with mucopolysaccharidosis type II shows evidence that the IDS gene is prone to splicing mutations

Mucopolysaccharidosis type II (MPS II) is an X-linked recessive lysosomal storage disease caused by a defect in the iduronate-2-sulfatase gene (IDS). Alternative splicing of the IDS gene can occur and the underlying regulatory mechanism may be rather complex. Nevertheless, little information is available on the role of variations at the IDS locus in the splicing process. Here we report that splice mutations at the IDS locus are an important source of MPS II pathogenicity, accounting for almost 56% of Portuguese cases. Among 16 unrelated Portuguese MPS II patients, 15 different mutations were identified: six intronic splice mutations (c.104-2AG, c.241-2A>G, c.241-1G>A, c.418+1G>A, c.880-8AG and c.1181-1G>C); two exonic splice mutations (c.1006G>lC and c.1122C>T); five missense mutations (D269V, D69V, D148N, R88C and P86L); one nonsense mutation (Q465Ter); one total IDS gene deletion; and one rearrangement involving a IDS gene inversion. Furthermore, nine of the 15 detected mutations affected the usual splicing pattern at the locus. Some of them are responsible for dramatic changes in the splicing mechanism. For example, the substitution mutation, c.418+1G>A, revealed the presence of an exonic sequence inside intron 3. Our study provides evidence that the IDS locus is prone to splicing mutations and that such susceptibility is particularly high in exon 3 and neighbouring regions. Consequently, mutation screening of the IDS gene cannot be restricted to gDNA examination. Unless cDNA analysis is also conducted, misclassifications as silent or missense mutations can be produced and even uncharacteristic splice-site mutations can be misinterpreted as classic splicing defects that may generate severe, unconventional splicing alterations.

Mutations in TMEM76* cause mucopolysaccharidosis IIIC (Sanfilippo C syndrome)

Mucopolysaccharidosis IIIC (MPS IIIC, or Sanfilippo C syndrome) is a lysosomal storage disorder caused by the inherited deficiency of the lysosomal membrane enzyme acetyl-coenzyme A: alpha -glucosaminide N-acetyltransferase (N-acetyltransferase), which leads to impaired degradation of heparan sulfate. We report the narrowing of the candidate region to a 2.6-cM interval between D8S1051 and D8S1831 and the identification of the transmembrane protein 76 gene (TMEM76), which encodes a 73-kDa protein with predicted multiple transmembrane domains and glycosylation sites, as the gene that causes MPS IIIC when it is mutated. Four nonsense mutations, 3 frameshift mutations due to deletions or a duplication, 6 splice-site mutations, and 14 missense mutations were identified among 30 probands with MPS IIIC. Functional expression of human TMEM76 and the mouse ortholog demonstrates that it is the gene that encodes the lysosomal N-acetyltransferase and suggests that this enzyme belongs to a new structural class of proteins that transport the activated acetyl residues across the cell membrane.

Mutation and polymorphism spectrum of the GALNS gene in mucopolysaccharidosis IVA (Morquio A)

Mucopolysaccharidosis IVA (MPS IVA; Morquio A disease) is an autosomal-recessive disorder caused by a deficiency of lysosomal N-acetylgalactosamine-6-sulfate sulfatase (GALNS; E.C.3.1.6.4). GALNS is required to degrade glycosaminoglycans, keratan sulfate (KS), and chondroitin-6-sulfate. Accumulation of undegraded substrates in lysosomes of the affected tissues leads to a systemic bone dysplasia. We summarize information on 148 unique mutations determined to date in the GALNS gene, including 26 novel mutations (19 missense, four small deletions, one splice-site, and two insertions). This heterogeneity in GALNS gene mutations accounts for an extensive clinical variability within MPS IVA. Seven polymorphisms that cause an amino acid change, and nine silent variants in the coding region are also described. Of the analyzed mutant alleles, missense mutations accounted for 78.4%; small deletions, 9.2%; nonsense mutation, 5.0%; large deletion, 2.4%; and insertions, 1.6%. Transitional mutations at CpG dinucleotides accounted for 26.4% of all the described mutations. The importance of the relationship between methylation status and distribution of transitional mutations at CpG sites at the GALNS gene locus was elucidated. The three most frequent mutations (over 5% of all mutations) were represented by missense mutations (p.R386C, p.G301C, and p.I113F). A genotype/phenotype correlation was defined in some mutations. Missense mutations associated with a certain phenotype were studied for their effects on enzyme activity and stability, the levels of blood and urine KS, the location of mutations with regard to the tertiary structure, and the loci of the altered amino acid residues among sulfatase proteins.

Evidence-based recommendations for monitoring bone disease and the response to enzyme replacement therapy in Gaucher patients

BACKGROUND

Bone disease is a serious complication of Gaucher disease. Untreated, it can result in pain, permanent bone damage and disability. Enzyme replacement therapy reverses many of the clinical signs of Gaucher bone disease but early assessment and treatment, and regular monitoring, are essential in optimising outcomes.

SCOPE

In September 2005, a group of European experts met to review current knowledge and identify best practice and unmet needs in the monitoring of Gaucher bone disease and the response to enzyme replacement therapy.

METHODS

Medline searches of peer-reviewed literature (no date restrictions) were conducted and supplemented by additional information considered relevant by panellists to furthering discussions.

FINDINGS AND CONCLUSIONS

The group's recommendations included: currently used biochemical bone markers are not clinically practical or reliable; plain X-rays should not be the sole method of assessing bone disease; MRI is the most sensitive method for monitoring bone marrow infiltration by Gaucher cells; semi-quantitative methods for assessing bone marrow infiltration in routine clinical practice should use readily available technology, include an assessment of Gaucher cell infiltration in the lumbar spine and femur, and be validated for inter-rater reliability and in comparison to other methods; a multidisciplinary approach is required for the treatment of Gaucher patients; all Gaucher patients should receive a comprehensive initial radiologic evaluation for bone disease and ongoing radiological monitoring at least once every 2 years.

Evidence for a link between sphingolipid metabolism and expression of CD1d and MHC-class II: monocytes from Gaucher disease patients as a model

Gaucher disease (GD) is an autosomal recessive inherited defect of the lysosomal enzyme glucocerebrosidase (GluCerase) that leads to glucosylceramide (GluCer) accumulation. We previously demonstrated the existence of imbalances in certain lymphocyte populations in GD patients. We now show that GluCerase-deficient monocytes from GD patients or monocytes from healthy subjects treated with conduritol-B-epoxide (CBE), an irreversible inhibitor of GluCerase activity, display high levels of surface expression of the lipid-binding molecule CD1d. GluCerase-deficient monocytes from GD patients also showed increased surface expression of major histocompatibility complex (MHC)-class II, but not of other lysosomal trafficking molecules, such as CD63 and MHC-class I. However, CD1d and MHC-class II mRNA levels were not increased. GluCerase-deficient monocytes from GD patients undergoing enzyme replacement therapy also exhibited increased levels of CD1d and MHC-class II and imbalances in the percentage of CD4+, CD8+, and Valpha24+ T cells. Interestingly, follow-up studies revealed that enzyme replacement therapy induced a decrease in MHC-class II expression and partial correction of the CD4+ T cell imbalances. These results reveal a new link between sphingolipid accumulation in monocytes and the expression of certain MHC molecules that may result in imbalances of regulatory T cell subsets. These immunological anomalies may contribute to the clinical heterogeneity in GD patients.