The study, “Racial differences in systemic sclerosis disease presentation: a European Scleroderma Trials and Research group study,” was published in the journal Rheumatology.
Prevalence and clinical symptoms of scleroderma vary among different racial groups. Studies of multi-racial populations of African Americans, Hispanics, and European descendants suggest that non-Europeans are at greater risk of severe disease and indicate that scleroderma’s incidence is higher in African Americans.
A deeper understanding of the role that race plays in scleroderma development could have important implications for its monitoring, treatment, and prognosis.
In the study, an international team investigated differences in scleroderma manifestations between white, Asian, and black patients. They also analyzed the effects of geographical location by comparing disease outcomes in black patients living in sub-Saharan Africa with those living abroad, as well as Asian patients living in Asia with those outside of Asia.
The study used the multinational European Scleroderma Trials and Research group database. A total of 9,161 white (mean age of 56.7), 341 Asian (46.3 years), and 198 black (45.6 years) patients were included.
Results revealed several differences across the three racial groups. Black patients showed the earliest onset of symptoms apart from Raynaud’s phenomena, which refers to numb, prickly, and frigid fingers and toes in response to cold or stress. They were followed by Asian patients, whose disease evolved more rapidly than in whites.
In addition, Asian patients had anti-topoisomerase-I autoantibodies (ATA; also known as anti-Scl-70) more frequently, but anti-centromere autoantibodies less commonly compared with white patients. Black patients were less likely than whites to have either antibody.
Of note, screening for these autoantibodies — immune proteins that mistakenly target a person’s own tissues or organs — is routine practice for the early diagnosis of scleroderma.
Topoisomerase-I is a crucial enzyme for the winding of DNA molecules during gene expression and cell division. It is highly specific to scleroderma and linked to diffuse skin disease and lung fibrosis, or scarring. The centromere is a part of chromosomes, and its autoantibodies are typically detected in limited cutaneous scleroderma.
Diffuse skin involvement was more prevalent in black patients than in whites, and rarer in Asians. Compared to white patients, both Asian and black patients were more than twice as likely to develop pulmonary hypertension and have poorer lung function (reflected by a lower forced vital capacity, the amount of air a person can exhale during a forced breath).
Asian patients also were the most susceptible to problems in their diffusing capacity of the lung, which refers to how well the lungs exchange gases with the blood.
The risk of death also differed across groups. Following the onset of Raynaud’s phenomena, Asian and black patients had increased mortality risk compared to whites (1.6-fold higher in Asians and 2.1 times higher in black patients). The team also saw that most of the racial effects appeared to be largely independent of where the patients lived.
“In summary, this analysis is by far the largest direct comparison of different ethnicities so far; it strengthens knowledge about the clinical and serological differences between [black patients] and [white patients] and largely extends that on [Asian patients] by suggesting that they have a relatively fast disease evolution in conjunction with high prevalences of ATA, [pulmonary hypertension] and lung involvement,” the researchers wrote.