Background/Purpose:
Systemic sclerosis (SSc) is a rare autoimmune disease categorized on the basis of skin involvement as either limited or diffuse cutaneous SSc, the latter of which manifests in more severe skin and internal organ involvement. SSc disproportionately affects women and literature suggests African American (AA) patients experience autoimmune diseases differently than other ethnic/racial groups. We sought to validate these observations utilizing a longitudinal cohort of SSc patients, comparing disease characteristics between AAs and non-AAs.

Methods:

Data were collected as part of an ongoing IRB-approved longitudinal registry of SSc patients, including demographics, clinical disease manifestations and other medical history. Patients were seen over a 12-year period at a single academic center. Retrospective chart review was additionally performed to confirm age of onset, SSc disease type, and selected criteria for SSc to assess severity of disease. PearsonÕs chi-squared and FisherÕs Exact testing were performed for categorical measures.  Two-sample t-tests were performed for continuous measures.  Significance was set at alpha = 0.05.

Results:

A total of 236 patients with SSc (80.9% female, 35.2% AA) were identified. Demographics and clinical characteristics are shown in Table 1. AA patients developed SSc at a significantly younger age compared to the non-AA patient subset (41.8±13.3 yrs., 48.7±13.2 yrs., respectively, p<0.01). Females developed SSc at a younger age than males (45.1±13.9 yrs., 51.3±11.0 yrs, p<0.01).  Diffuse SSc was significantly more common in AA patients (p<0.01). Males overall were more likely to have diffuse SSc than limited SSc (68.3%, p<0.01).

Interstitial lung disease was significantly more common in AA patients (68.5%, p=0.02).  The higher prevalence of lung disease among AAs was not attributed to smoking status, as a significantly higher proportion of non-black SSc patients were smokers.   Although not statistically significant, AA patients had a higher prevalence of restrictive lung disease based on forced vital capacity percent predicted <70% (46.0% versus 31.9% p=NS).  Overall mortality was 7.2% in AA patients compared to 3.9% in non-AA patients with SSc (p=NS). 

Conclusion:

In conclusion, we found that AA SSc patients tend to be younger and more often have diffuse cutaneous disease than non-AA SSc patients, consistent with findings among other AA populations.  Although not statistically significant, AA patients trended towards a higher prevalence of restrictive lung pattern on pulmonary function testing and a higher mortality rate.  These data support the conclusion that AAs have more severe disease with a more unfavorable SSc prognosis. Further investigation into the multifactorial causes for this disparity is needed in order to identify strategies to reduce them.