Background Lymphangioleiomyomatosis (LAM) is a rare disease of women categorised by lung cysts, lymphatic abnormalities and angiomyolipomas; a benign tumour occurring chiefly in the kidneys. Although benign, the tumours can enlarge causing symptoms and those over 4cm are prone to haemorrhage which can result in nephrectomy. LAM can occur in isolation (sporadic LAM) or associated with tuberous sclerosis complex (TSC-LAM). Treatment guidelines for angiomyolipoma tend to be based on retrospective series often from patients with TSC. The natural history of angiomyolipoma in sporadic LAM is not well understood.

Aims To document the natural history, risk factors for, and clinical features associated with, angiomyolipoma in a national cohort of patients with sporadic and TSC-LAM to plan clinical screening programs.

Methods Demographic data, clinical features, lung function and tumour size were obtained from clinical records of patients attending the National Centre for LAM in Nottingham. Tumour size was recorded as the longest tumour diameter on any imaging modality. Tumours smaller than 10mm were assigned a value of 10mm. Ethical approval for use of patient data was obtained and patients gave informed consent.

Results 122 patients with definite or probable LAM by European Respiratory Society criteria were identified. Of these, 68 (56%) had at least one angiomyolipoma. Angiomyolipoma were present in 50% of patients with sporadic LAM and all patients with TSC-LAM. Those with sporadic LAM tended to have smaller tumours than those with TSC-LAM (31mm (SD 27) vs. 49mm (SD 27) respectively), were less often bilateral (40 vs. 79%), were less likely to bleed (17 vs. 31%) and less likely to require surgery or embolisation (49 vs. 66%). Serial tumour measurements were available from some patients, tumours from those with TSC-LAM grew at 3.8 mm/year (n=6, SD 14.2) tumour growth in sporadic LAM growth was 4.3 mm/year (n=16, SD 8.2. p=0.46).

Conclusions Angiomyolipomas are common in patients with sporadic and TSC-LAM. The tumours require intervention more frequently in TSC than sporadic LAM. The two patient groups may require different angiomyolipoma management.