Primary biliary cirrhosis: geographical clustering and symptomatic onset seasonality.
Patients with primary biliary cirrhosis (primary non-suppurative destructive cholangitis) in the north east region of England were studied over a five year period and, to evaluate epidemicity, compared with two contemporaneous disease series of known occurrence. These were: terminal renal failure, all causes (low or absent epidemicity n = 106) and an outbreak of echovirus 19 disease (high epidemicity n = 201). Eight primary biliary cirrhosis-affected men and 109 women from an estimated catchment population of 2.08 million were identified. The current diagnosis rate was 1.0/100 000 (1.8/100 000 for women of 15 or more). There were 18 deaths, mean survival from diagnosis 4.0 years. Within the region prevalence varied from 3.7/100 000 in rural areas to 14.4/100 000 in industrial urban areas. In the conurbation, prevalence rates varied insignificantly. Here, most cases were concentrated in central districts, where the proportion of asymptomatic presentations was 50%. Outside the conurbation the asymptomatic proportion fell to 21%, suggesting low incidental diagnosis rates. When compared with echovirus 19, primary biliary cirrhosis was of low or absent epidemicity, and similar to renal failure in its uniform geographical distribution and lack of clustering. Forty three patients (37% of the total), however, had significantly seasonal symptomatic presentations (p less than 0.01), although scan statistic testing failed to show clustering of onset in time. Apparently provocative factors associated with primary biliary cirrhosis symptomatic onset were identified in only 11 (9.4%) of patients. Age-specific onset rates rose linearly between ages 35 and 65, and nearly one third of patients presented after 65 years, two thirds of deaths occurring in this age group. There is thus no evidence in north east England of geographical anomalies in the distribution of primary biliary cirrhosis. International differences may be partly explained by environmental factors influencing seasonal presentation, such as sunlight. Diagnosis rates are profoundly influenced by increased medical awareness, especially in the elderly, of this now relatively common disease and increased use of the mitochondrial (AMA) antibody test.