Glycosaminoglycan linkage region of urinary bikunin as a potentially useful biomarker for ß3GalT6-deficient spondylodysplastic Ehlers-Danlos syndrome.

The spondylodysplastic type of Ehlers-Danlos syndrome (spEDS) is caused by genetic defects in the B4GALT7 or B3GALT6 genes both deranging the biosynthesis of the glycosaminoglycan linkage region of chondroitin/dermatan sulfate and heparan sulfate proteoglycans. In this study, we have analyzed the linkage regions of urinary chondroitin sulfate proteoglycans of three siblings, diagnosed with spEDS and carrying biallelic pathogenic variants of the B3GALT6 gene. Proteoglycans were digested with trypsin, glycopeptides enriched on anion-exchange columns, depolymerized with chondroitinase ABC, and analyzed by nLC-MS/MS. In urine of the unaffected mother, the dominating glycopeptide of bikunin/protein AMBP appeared as only one dominating (99.9%) peak with the canonical tetrasaccharide linkage region modification. In contrast, the samples of the three affected siblings contained two different glycopeptide peaks, corresponding to the canonical tetrasaccharide and to the non-canonical trisaccharide linkage region modifications in individual ratios of 61/38, 73/27, and 59/41. We propose that the relative distribution of glycosaminoglycan linkage regions of urinary bikunin glycopeptides may serve as a phenotypic biomarker in a diagnostic test but also as a biomarker to follow the effect of future therapies in affected individuals.

Biallelic B3GALT6 mutations cause spondylodysplastic Ehlers-Danlos syndrome.

Proteoglycans are among the most abundant and structurally complex biomacromolecules and play critical roles in connective tissues. They are composed of a core protein onto which glycosaminoglycan (GAG) side chains are attached via a linker region. Biallelic mutations in B3GALT6, encoding one of the linker region glycosyltransferases, are known to cause either spondyloepimetaphyseal dysplasia (SEMD) or a severe pleiotropic form of Ehlers-Danlos syndromes (EDS). This study provides clinical, molecular and biochemical data on 12 patients with biallelic B3GALT6 mutations. Notably, all patients have features of both EDS and SEMD. In addition, some patients have severe and potential life-threatening complications such as aortic dilatation and aneurysm, cervical spine instability and respiratory insufficiency. Whole-exome sequencing, next generation panel sequencing and direct sequencing identified biallelic B3GALT6 mutations in all patients. We show that these mutations reduce the amount of ß3GalT6 protein and lead to a complete loss of galactosyltransferase activity. In turn, this leads to deficient GAG synthesis, and ultrastructural abnormalities in collagen fibril organization. In conclusion, this study redefines the phenotype associated with B3GALT6 mutations on the basis of clinical, molecular and biochemical data in 12 patients, and provides an in-depth assessment of ß3GalT6 activity and GAG synthesis to better understand this rare condition.

Laboratory and imaging studies used by French rheumatologists to evaluate patients with early arthritis.

OBJECTIVE: To conduct a practice survey of laboratory and imaging studies used by French rheumatologists to identify the cause of recent-onset arthritis. METHODS: We selected a random sample of 210 rheumatologists, who were asked to recruit all patients with recent-onset arthritis (at least one joint involved, for less than one year) during a 2 week period, and to record laboratory and imaging studies performed. Results were analyzed in the overall group, in diagnostic subgroups, and in clinical presentation subgroups. RESULTS: The 119 rheumatologists who participated recruited 104 patients. Investigations done in 50% to 75% of patients were blood cell counts; erythrocyte sedimentation rate; serum assays of C-reactive protein, rheumatoid factors, antinuclear antibodies; and hand radiographs. Investigations in 50% to 74% of patients were serum ASAT/ALAT, creatinine, and uric acid; and foot radiographs. Finally, 25% to 49% of patients were tested for proteinuria; antikeratin antibodies; hepatitis B, hepatitis C, and Lyme serologies; creatine phosphokinase; blood iron; HLA-B27; and radiographs of chest and pelvis. No differences were found between investigations in patients with suspected rheumatoid arthritis and/or undifferentiated arthritis and those in other patients. In contrast, suspected diagnoses and presence of extraarticular manifestations classically associated with specific diseases modified the selection of investigations. CONCLUSION: Although considerable variability occurred, our study suggests that a limited panel of laboratory and imaging studies is performed in at least 25% of patients with recent-onset arthritis, regardless of clues suggesting a specific diagnosis.

Costs of workups for the diagnosis of early arthritis: results of a nationwide survey.

OBJECTIVE: To evaluate the costs of workups to diagnose early arthritis. METHODS: In 2000, the French Society for Rheumatology conducted a survey of a representative sample of French and Belgian rheumatologists (n = 239). The respondents were asked to consider 2 hypothetical scenarios, 1 describing undifferentiated arthritis and the other more suggestive of rheumatoid arthritis. They were then asked what diagnostic workup they would order. Costs for each study were determined in 2001 euros, according to the French public health system fee schedules. RESULTS: In total, 151 rheumatologists participated in the study (63%). The mean +/- SD diagnostic costs were 406.5 +/- 194.3 euro for the case with no diagnostic clues, and 280.7 +/- 154.3 euro for the case suggestive of early RA. Responses were very heterogeneous. The 2 main sources of expenditure were immunology tests and imaging. Hospital staff physicians tended to order more expensive workups, and costs tended to vary inversely with physician experience. The most important predictor of cost was diagnostic doubt, as estimated by the number of diagnoses proposed by respondents in each case; each additional diagnosis cost an additional 19.1-26.1 euro. CONCLUSION: Diagnostic workups after a first medical visit for early polyarthritis result in substantial direct costs. This observation and the great variability observed in physicians' practices point out the need for consensus on the appropriate workups for these patients.

Assessment of disease activity in rheumatoid arthritis with (18)F-FDG PET.

UNLABELLED: The aim of this study was to assess synovitis by (18)F-FDG PET in an individual joint analysis and in a global analysis of rheumatoid arthritis (RA) disease activity and to compare (18)F-FDG PET parameters with clinical, biologic, and sonographic (US) rheumatoid parameters. METHODS: Three hundred fifty-six joints were assessed in 21 patients with active RA: the knees in all subjects and either wrists as well as metacarpophalangeal and proximal interphalangeal joints in 13 patients, or ankles and the first metatarsophalangeal joints in the remaining 8 patients. PET analysis consisted of a visual identification of (18)F-FDG uptake in the synovium and measurements of standardized uptake values (SUVs). Independent assessors performed the clinical and US examinations. RESULTS: PET positivity was found in 63% of joints, whereas 75%, 79%, and 56% were positive for swelling, tenderness, and US analysis, respectively. Both the rate of PET-positive joints and the SUV increased with the number of positive parameters present (swelling, tenderness, US positivity) and with the synovial thickness. The mean SUV was significantly higher in joints where a power Doppler signal was found. In a global PET analysis, the number of PET-positive joints and the cumulative SUV were significantly correlated with the swollen and tender joint counts, the patient and physician global assessments, the erythrocyte sedimentation rate and C-reactive protein serum levels, the disease activity score and the simplified disease activity index, the number of US-positive joints, and the cumulative synovial thickness. CONCLUSION: (18)F-FDG PET is a unique imaging technique that can assess the metabolic activity of synovitis and measure the disease activity in RA.

Rheumatoid hand joint synovitis: gray-scale and power Doppler US quantifications following anti-tumor necrosis factor-alpha treatment: pilot study.

PURPOSE: To evaluate by using B-mode and power Doppler ultrasonography (US) and clinical assessment the response of hand joint synovitis in patients with active rheumatoid arthritis (RA) to treatment with the anti-tumor necrosis factor-alpha agent infliximab. MATERIALS AND METHODS: Wrists, metacarpophalangeal (MCP) joints, and proximal interphalangeal (PIP) joints in 11 patients with active RA were assessed before and 6 weeks after three infliximab infusions. US assessment was performed at a single site in the MCP and PIP joints and at two sites (radiocarpal and intercarpal) in the wrists. Twenty measurements were performed in the wrists; 110 measurements, in the MCP joints; and 103 measurements, in the PIP joints. Two wrists and seven PIP joints were excluded owing to complete joint destruction. US parameters (synovial thickness, number of US-positive joints [ie, with synovial thickness > or = 1 mm], cumulative synovial thickness index, and presence of Doppler signal) and clinical parameters (swollen joint count) were independently assessed and compared with baseline values by using the McNemar chi2 and paired Student t tests. RESULTS: After infliximab treatment, there was a significant decrease in the mean numbers of swollen and US-positive joints and in the cumulative synovial thickness (P <.05). The mean synovial thickness decreased in all joints swollen at baseline and in the MCP and PIP joints not swollen at baseline (P <.01). Change from baseline cumulative synovial thickness correlated significantly with change in disease activity score (r = 0.69, P <.05). The number of positive Doppler US signals decreased significantly (in 13 US-positive joints at baseline, in five after treatment; P <.05). CONCLUSION: US is a feasible imaging modality for measurement of the response of RA small-joint synovitis to therapy.