Natural history of incidental sporadic or tuberous sclerosis complex associated lymphangioleiomyomatosis

The majority of patients who require medical intervention for lymphangioleiomyomatosis have the sporadic form of the disease (S-LAM). Some data suggested that TSC associated LAM could be a milder disease compared to S-LAM. Systematic screening for LAM using chest CT scan in TSC patients, could lead to a pre-clinic identification of LAM. To investigate whether the different disease behaviour is real or due to overdiagnosis of screened TSC women, we compared the natural history of S-LAM and TSC-LAM in patients with incidental diagnosis. A retrospective study involving outpatients with S-LAM and TSC-LAM followed in two hospitals in Milan, Italy and Sao Paolo, Brazil from 1995 to2017 was conduced. Incidental LAM diagnosis was defined by the finding of lung cysts in the abdominal (upper slices) or chest CT scans performed for reasons other than symptoms due to LAM. Clinical and functional data from 52 patients (23 with S-LAM and 29 with TSC-LAM) were analysed. There was no difference in yearly rate of functional decline between TSC-LAM, and S-LAM patients: At diagnosis functional impairment was mild without differences between groups. Patients with S-LAM had a trend to more severe cystic involvement but less renal angiomyolipoma, and lower VEGF-D serum levels than TSC-LAM. The natural history of TSC-LAM and S-LAM, when a potential selection bias due to screening in the latter group is balanced, is similar.