Systemic lupus erythematosus (SLE) patients of Mexican ancestry living in Texas appear to have a shorter time to occurrence of initial damage compared to Hispanic patients living in Puerto Rico and Caucasian patients,1 according to a new study published in Arthritis & Rheumatism.

"It is important for clinicians to know that patients of Mexican ancestry may have a worse outcome than Caucasian patients or Hispanic patients from the island of Puerto Rico," said study co-investigator Graciela S. Alarcón, MD, a professor of medicine at the University of Alabama at Birmingham. "Hispanic patients of Mexican ancestry may need to be managed more closely and more carefully."

The investigators found that initial damage occurred in 54 patients (34%); 21 were Hispanic patients living in Texas (39%), 21 were African American patients (39%), 10 were Caucasian patients (19%), and 2 were Hispanic patients living in Puerto Rico (4%). The most frequently identified initial damage involved renal disorders (primarily proteinuria) in Hispanic patients who reside in Texas and in African American patients, integumentary damage (primarily scarring alopecia) in Hispanic patients living in Puerto Rico, and ocular conditions (primarily cataracts) in Caucasian patients.

"I think it is a combination of genetics and socioeconomic factors," Dr. Alarcón said in an interview with CIAOMed. "We think genetics may predispose patients to the disease itself but the course of the disease is significantly impacted by socioeconomic factors. "We have been studying 2 types of Hispanics. We are distinguishing them because they seem to have 2 different diseases. They have diseases of different characteristics and different outcomes."

Dr. Alarcón and her colleagues examined the factors predisposing to initial damage in patients in the LUMINA (lupus in minorities: nature versus nurture) cohort, a designated group of multiethnic patients with SLE in the US. The investigators tracked 158 LUMINA patients with no damage at baseline according to the Systemic Lupus International Collaborating Clinics Damage Index (SDI) and with disease duration of less than 6 months. All the subjects were followed for a median of 24 months (range 5-112 months).

In the present study, damage was assessed from baseline to the last visit and predictors of time to initial damage were examined by univariable and multivariable Cox proportional hazard regression models. Previously, these researchers had reported that the factors predictive of damage accrual were Hispanic ancestry (primarily Mexican) of Texas residents, older age, glucocorticoid use, and disease activity.2 However, the prior analyses did not take into account that damage was present when the patients entered the study.

It has been demonstrated that the existence of previous damage predisposes an SLE patient to the accrual of further damage.3 Thus, the current investigators expanded their observations to include factors that predispose to a shorter time to initial damage. They looked at patients without damage upon entry into the LUMINA cohort, patient characteristics, and time to initial damage. The majority of the 158 patients were women (97%) with a wide distribution of age (16-67 years). The mean age was 34 years.

Independent predictors of a shorter time to initial damage were Hispanic ethnicity of patients living in Texas, greater disease activity according to the Systemic Lupus Activity Measure, the occurrence of thrombotic events in visceral and/or peripheral veins or arteries, and use of prednisone at a dosage of less than 10 mg per day. Prednisone in doses of 10 to 30 mg per day was found to be protective against the occurrence of initial damage.

"Genetics is very important in SLE patients, but unfortunately there are multiple genetic defects that can occur, including complement deficiencies, apoptotic defects, receptor defects, etcetera, which all play a part in susceptibility," commented Terry L. Moore, MD, director of the division of rheumatology and pediatric rheumatology and a professor of internal medicine, pediatrics, and molecular microbiology and immunology at St. Louis University School of Medicine in Missouri. "The study itself probably does not have enough power to have a great deal of clinical significance, but we have always known that Hispanic patients seem to have more aggressive disease. Therefore, each person on diagnosis should have a complete evaluation of all organ systems."

Overall, it was noted that Hispanic patients who reside in Texas remained free of damage for the shortest time and Caucasian patients, for the longest time. Dr. Alarcón noted that, given the fact that damage predicts the occurrence of further damage, a better understanding of the factors that predispose a patient to the onset of damage may have important clinical applications.

Improved understanding of these factors in SLE patients is critical for the development of preventive therapeutic interventions.1 Dr. Moore observed that the recent study is very important because it may help lead to improved ways of managing individual patients. However, he pointed out that this is only one study and ongoing research will be needed to better understand what may be contributing to initial damage in various ethnic groups.

References:

Toloza SMA, Roseman JM, Alarcón GS, et al, for the LUMINA Study Group. Systemic lupus erythematosus in a multiethnic US cohort (LUMINA). XXII. Predictors of time to the occurrence of initial damage. Arthritis Rheum. 2004;50:3177-3186.

Alarcón GS, McGwin G Jr, Bartolucci AA, et al. Systemic lupus erythematosus in three ethnic groups. IX. Differences in damage accrual. Arthritis Rheum. 2001;44:2797-2806.

Alarcón GS, Roseman JM, McGwin G Jr, et al. Systemic lupus erythematosus in three ethnic groups. XX. Damage as predictor of further damage. Rheumatology (Oxford). 2004;43;349-352.