Characterization of damage in Portuguese lupus patients.

Sir, We read with interest the report ‘Characterization of damage in Portuguese lupus patients: analysis of a national lupus registry’ and wish to emphasize that the frequency and cumulative damage score present in a lupus patient population is also determined by the type of organ damage. In the registry study of 976 patients by Gonçalves et al., the average SDI score was 0.71 1.22 and the frequency of damage was 37.4% after a 17 9.4 year follow-up. This was considered by the authors to be lower in Portuguese patients when compared to other series, namely the University College London Hospital (UCLH) cohort which reported 50% damage at 10 year follow-up and the SLICC cohort, which observed 51% damage at six years follow-up. Of note, in the UCLH cohort, when measured between 15 and 20 years of follow-up, most of the damage accrual occurred in the musculoskeletal system. A recent retrospective study of our single-centre hospital-based cohort consisting of 98 Portuguese lupus patients, in which every patient was clinically evaluated at the time of study completion, revealed a similar frequency of accrued damage equally measured by SDI values 1. In comparison, although our cohort comprised a similar frequency of articular disease (approximately 70%), there was a higher frequency of neuropsychiatric (NP) disease (22%) than in the national register (11%). In addition, in our cohort, the patients with damage were enriched for NP disease (n1⁄4 16/22, 72%) versus non-NP patients (n1⁄4 17/76, 22%). Our average SDI scores were higher: 2.31 1.25 for the NP and 1.53 0.80 for the non-NP group. This difference was statistically significant (P1⁄4 0, 0001) and was largely due to damage of the neurologic system that occurred in 14 of the 16 NP patients. Both NP and non-NP patients had a similar mean age and disease duration (age: 44 12 and 45 14 years, disease duration: 13 7 and 13 8 years, respectively). SDI scores increased with the duration of the disease in both groups, and were initially 0.44 0.89 for NP and 0 for non-NP patients. It is well conceivable that Lupus patients with a predominant articular phenotype should have low damage accrual after a long follow-up. However, this is a very heterogeneous disease, and this subset of patients is not representative of the overall population of lupus patients, when other clinical phenotypes are taken into consideration.