Updated Prevalence of Lymphangioleiomyomatosis in Northern Europe

<bold>Introduction</bold>: LAM is a low-grade metastasizing neoplasm that causes cystic lung disease. It almost exclusively impacts females and is sporadic or associated with Tuberous Sclerosis Complex. It is rare, with a reported prevalence of 3-8 cases per million women. Identifying patients with LAM is important as effective therapy is available. We aimed to assess the prevalence of LAM in Europe. <bold>Methods:</bold>Data on the number of patients with LAM in centres across 4 European countries was collated including whether the patient had a diagnosis of TSC- or Sporadic LAM. Census data from each country was used to calculate the number of cases of LAM per total female population and per adult female population. <bold>Results:</bold> A total of 351 individuals with a confirmed diagnosis of LAM were identified across 4 European countries (Ireland, Norway, The Netherlands, Denmark). Sisty-six percent (n =232) had sporadic LAM. Thirty four percent (n = 119) had TSC-LAM. The estimated prevalence of LAM per million adult females ranged from 22.46 (95% CI; 19.29 - 26.16) in The Netherlands to 26.37 (95% CI; 20.17 – 34.49) in Ireland. Pooled prevalence across all countries was estimated at 23.5 cases per million adult females (95% CI; 20.95 – 26.04, Tau2 = 0; Chi2 = 1.06; df = 3; I2 = 0%, Figure 1), or 19.01 (95%CI; 16.95 – 21.06) per million when considering the total living female population (all ages). <bold>Discussion</bold>: Our data suggests the prevalence of LAM is 23.5 per million adult women, higher than the reported worldwide prevalence. This is likely still an underestimate. Reporting data from smaller countries with similar national health services, patient numbers likely represent a truer prevalence that previously reported.