Gene-level association analysis of systemic sclerosis: A comparison of African-Americans and White populations

Gene-level analysis of ImmunoChip or genome-wide association studies (GWAS) data has not been previously reported for systemic sclerosis (SSc, scleroderma). The objective of this study was to analyze genetic susceptibility loci in SSc at the gene level and to determine if the detected associations were shared in African-American and White populations, using data from ImmunoChip and GWAS genotyping studies. The White sample included 1833 cases and 3466 controls (956 cases and 2741 controls from the US and 877 cases and 725 controls from Spain) and the African American sample, 291 cases and 260 controls. In both Whites and African Americans, we performed a gene-level analysis that integrates association statistics in a gene possibly harboring multiple SNPs with weak effect on disease risk, using Versatile Gene-based Association Study (VEGAS) software. The SNP-level analysis was performed using PLINK v.1.07. We identified 4 novel candidate genes (STAT1, FCGR2C, NIPSNAP3B, and SCT) significantly associated and 4 genes (SERBP1, PINX1, TMEM175 and EXOC2) suggestively associated with SSc in the gene level analysis in White patients. As an exploratory analysis we compared the results on Whites with those from African Americans. Of previously established susceptibility genes identified in Whites, only TNFAIP3 was significant at the nominal level (p = 6.13x10-3) in African Americans in the gene-level analysis of the ImmunoChip data. Among the top suggestive novel genes identified in Whites based on the ImmunoChip data, FCGR2C and PINX1 were only nominally significant in African Americans (p = 0.016 and p = 0.028, respectively), while among the top novel genes identified in the gene-level analysis in African Americans, UNC5C (p = 5.57x10-4) and CLEC16A (p = 0.0463) were also nominally significant in Whites. We also present the gene-level analysis of SSc clinical and autoantibody phenotypes among Whites. Our findings need to be validated by independent studies, particularly due to the limited sample size of African Americans.

Evidence that deletion at FCGR3B is a risk factor for systemic sclerosis

There is increasing evidence that gene copy number (CN) variation influences clinical phenotype. The low-affinity Fc receptor 3B (FCGR3B) located in the FCGR gene cluster is a CN polymorphic gene involved in the recruitment of polymorphonuclear neutrophils to sites of inflammation and their activation. Given the genetic overlap between systemic lupus erythematosus and systemic sclerosis (SSc) and the strong evidence for FCGR3B CN in the pathology of SLE, we hypothesised that FCGR3B gene dosage influences susceptibility to SSc. We obtained FCGR3B deletion status in 777 European Caucasian cases and 1000 controls. There was an inverse relationship between FCGR3B CN and disease susceptibility. CN of ≤ 1 was a significant risk factor for SSc (OR=1.55 (1.13-2.14), P=0.007) relative to CN ≥ 2. Although requiring replication, these results suggest that impaired immune complex clearance arising from FCGR3B deficiency contributes to the pathology of SSc, and FCGR3B CN variation is a common risk factor for systemic autoimmunity.

Bosentan in clinical practice for treating digital and other ischemic ulcers in Spanish patients with systemic sclerosis: IBER-DU cohort study

OBJECTIVE

To describe treatment outcomes and safety experience with bosentan in patients with systemic sclerosis (SSc) and digital ulcers (DU), in a clinical setting in Spain.

METHODS

This was a multicenter, noninterventional retrospective cohort study. Data were collected retrospectively from patients with DU, with or without pulmonary arterial hypertension (PAH), who were initiating bosentan therapy in 2003 (n = 26) or 2004 (n = 41) and followed until May 2005. Data were obtained from centers prescribing bosentan. Relevant measures included number of DU, occurrence of new DU, overall DU clinical status (improved, stabilized, worsened), and bosentan-associated adverse events.

RESULTS

Sixty-seven patients with SSc and DU or other ulcers were included. PAH was also present in 12 patients (18%). At the start of bosentan treatment, the median number of DU per patient was 3.0. The median change in number of DU was -3.6 and -5.0 at 12 and 24 months, respectively. Sixty-eight percent of the patients did not develop any new DU at 12 months. DU clinical status was reported at 12 months for 22 patients: 18 patients (81.8%) improved and 4 (18.2%) stabilized. The median treatment duration was 13.0 months. The main adverse event was increase of aminotransferase, observed in 5 patients (7%), leading to discontinuation of treatment in 3 patients (4.4%).

CONCLUSION

Previously reported results of bosentan efficacy in DU management are reproducible in clinical practice. This efficacy is maintained in the longterm followup. Bosentan treatment was well tolerated and adverse events were comparable with those observed in previous reports.

Survival prognostic factors and markers of morbidity in Spanish patients with systemic sclerosis

OBJECTIVE

To identify survival prognostic factors and markers of morbidity among patients with systemic sclerosis (SSc).

PATIENTS AND METHODS

The study included 72 patients diagnosed with SSc. According to the extent of skin involvement, three groups of patients were established: group 1, without sclerosis and with sclerosis of fingers and neck; group 2, with sclerosis of face and distal to elbows and knees; group 3, with generalised sclerosis including the trunk. All patients were included in a study protocol to determine visceral involvement. Cumulative survival after first symptom has been estimated according to the Kaplan-Meier method. The association between a hypothetical prognostic factor and cumulative survival after first symptom was assessed by log rank test. The association between a hypothetical risk factor and the prevalence of severe morbidity was assessed by the odds ratio. Multiple logistic regression models were used to identify the main predictors of severe morbidity.

RESULTS

Survival was estimated to be 85% 10 years after first SSc symptom. Survival was higher among SSc patients with skin involvement distal to elbows and knees than among the rest of patients; a forced vital capacity (FVC) on spirometry lower than 70% of expected value was associated with a shorter survival, even after adjustment for diffuse SSc. Skin involvement proximal to elbows or knees was associated with a higher prevalence of severe morbidity (OR = 46.57; p < 0.001). According to a multiple logistic regression, severe morbidity was higher among patients with skin involvement proximal to knees or elbows (OR = 40.92; p < 0.001) or among patients with pulmonary hypertension detected by Doppler echocardiography (OR = 23.66 p < 0.001).

CONCLUSIONS

In patients with SSc the extent of skin sclerosis was found to be a determining factor on the prognosis. According to skin sclerosis extent two main subsets of SSc patients with different survival incidence and degree of morbidity could be clearly established: limited SSc, formed by patients with no skin sclerosis or with sclerosis distal to elbows and knees and diffuse SSc, formed by patients with skin sclerosis distal and proximal to elbows and knees. Moreover, lung involvement (FVC < 70% on survival study and pulmonary hypertension on morbidity study) was an important and independent prognostic factor.

Behçet's disease and pregnancy relationship study

The effects of pregnancy on the course of Behçet's disease (BD), and vice versa, are unknown and little has been reported. We have studied three groups of women: (1) group A included 61 pregnancies in 23 women with BD, 25 pregnancies took place in 10 patients already diagnosed (group 1A) and 36 pregnancies occurred in 13 patients before disease diagnosis (group 2A); (2) group B included 30 females with 83 pregnancies affected by recurrent oral ulcers (ROU); (3) group C included 20 healthy women with 61 pregnancies. We investigated the effects of BD on pregnancy and fetal outcome, and the influence of gestation on the course of BD. A questionnaire was used in which specific information about each pregnancy, labour and puerperium was collected. We looked for medical confirmation in all cases where any pathology had been identified. No significant differences were found in the incidence of pregnancy complications between groups. The incidence of perinatal death was also similar and neither congenital abnormalities nor neonatal BD were observed. Only two patients observed a flare of the disease and in two cases the diagnosis of BD was made during the pregnancy. In our series, the outcome of pregnancy was generally good in BD patients, disease manifestations were not consistently worsened and fetal outcome was excellent. The first case of Budd-Chiari syndrome during the puerperium in a BD patient is reported.