GOTHENBURG, Sweden – Rapid progression of cutaneous lupus erythematosus to SLE occurs considerably more often than previously recognized, a comprehensive nationwide Swedish study found.
The population-based study, which included all 1,088 patients diagnosed with CLE in Sweden from 2005 to 2007, found that the risk of being diagnosed with SLE during the first year of CLE diagnosis was 12%. The 3-year rate of progression to SLE was 18%, Dr. Carina M. Grönhagen reported at the annual congress of the European Academy of Dermatology and Venereology.
Dr. Carina M. Grönhagen
Moreover, 24% of patients already carried the diagnosis of SLE at the time they were diagnosed with CLE, added Dr. Grönhagen, a dermatology resident at the Karolinska Institutet, Danderyd Hospital, Stockholm.
Patients with the subacute form of CLE had the highest rate of early progression to SLE, with a 3-year incidence of nearly 25%. Patients with subacute CLE accounted for 15.7% of the overall Swedish CLE cohort.
Discoid CLE accounted for 79.8% of all cases of CLE diagnosed in Sweden during the study period, while lupus panniculitis and other less common forms of local LE comprised the remainder.
Women with newly diagnosed CLE had a 3-year rate of progression to SLE of 20%, twice that of men. The incidence of CLE was threefold greater in Swedish women than men.
Patients with newly diagnosed CLE should be informed of the risk of early progression to SLE, Dr. Grönhagen said. They should be made aware of the systemic signs and symptoms, such as fevers and joint pains, so appropriate treatment for SLE is not delayed.
Her study relied upon Swedish National Patient Register data, which, since 2001, has included outpatient specialist care as well as inpatient care.
The incidence of CLE in Sweden, based on these data, is 4.0 per 100,000 population per year. The peak incidence of CLE in women was in the 65- to 74-year-old group, while the peak in men was at age 55-64. This pattern was skewed in the subset of patients with subacute CLE; their peak incidence was later, and there were far fewer cases diagnosed before age 45 than for discoid and other forms of CLE.
"One theory behind this is that the subacute form is drug induced to a larger extent than previously believed. An important known trigger for subacute CLE is antihypertensive drugs, which are mostly taken by people age 45 and older," Dr. Grönhagen said.
During her presentation at the meeting of the European Society of Cutaneous Lupus Erythematosus, held in conjunction with the EADV congress, audience members noted that there has been a dearth of population-based studies reporting the incidence of isolated CLE. They also commented on the large size of the population in Dr. Grönhagen’s study and the 3-year follow-up.
Audience members noted that the Swedish national study, since it included outpatients as well as inpatients, is relatively immune to selection bias. Although it was noted that the reported CLE incidence of 4.0/100,000 is up to 10-fold lower than cited in some other studies, Dr. Grönhagen countered that prior studies have been much smaller and less comprehensive.
Still, she said, the 4.0/100,000 incidence figure is probably an underestimate. It is likely that the mildest cases of discoid LE were never referred to a dermatologist or other specialist and, hence, weren't recorded in the outpatient portion of the national registry.
Dr. Grönhagen declared having no relevant financial interests.