On Systemic Lupus Erythematosus Clinical studies with special reference to epidemiology, lung function and complement activation

Abstract

SLE patients from a defined population (mean population at risk 158572) were monitored prospectively during 1981-1986. By the end of 1986, 86 patients (72 females, 14 males, median age 48) had been included in the cohort, the point prevalence being 68 patients (42/100 000 population at risk). The annual incidence was 4.0 cases/100 000/adults/year. A high completeness of retrieval of patients was achieved by computerized diagnosis and ANA registers in addition to clinical case finding. Five year survival in the prospective group was 97 percent. The proportion of patients with cutaneous manifestations, antibodies to dsDNA and hypocomplementemia decreased with increasing age at diagnosis, while the proportion of patients with serositis, secondary Sjögren's syndrome and antibodies to SSA increased.

Outcome was considered favorable, as witnessed by low mortality, low frequency of organ damage, and high percentage of patients gainfully employed. Disease flares occurred at a constant frequency after the first year. Patients with neuropsychiatric disease, drug hypersensitivity, persistent hypocomplementemia, antibodies to dsDNA and cardiolipin had a high frequency of relapse. Myocardial infarctions were nine times more common than in a Swedish control population and were related to long disease duration and glucocorticoid treatment.

Extensive lung function tests in twelve consecutive symptomatic patients revealed no functionally significant lung damage in the majority of the patients. Reduced working capacity was related to non-respiratory factors. Spirometry screening in the epidemiological cohort revealed only a moderate reduction of vital capacity in patients with a past history of serositis.

In prospective studies of C1 dissociation, the concentration of C1 IA complexes of the tetramer C1 IA-Clr-Cls-C1 IA variety correlated with the concentrations of C2 and C3 fragments, suggesting effective activation of the classical pathway. This was a characteristic finding in active SLE nephritis. Trimer C1 IA-C1r-C1s complexes were found in low amounts in nephritis, but in high concentrations in exharenal SLE, and probably reflected C1 activation controlled at the C1r level.

Key Words:

• Systemic lupus erythematosus
• incidence
• prevalence
• elderly
• outcome
• disease activity
• morbidity
• mortality
• lung function
• perfusion
• ventilation
• pulmonary hypertension
• chest symptoms
• classical complement pathway
• complement activation
• C1 inactivotor