Inclusion Criteria:

• If female, documentation of negative pregnancy test prior to enrolment.
• Participants, including males, must use an effective form of contraception, whilst taking sirolimus and for twelve weeks after stopping the drug
• One or more renal angiomyolipomata of at least two centimetres or greater in largest diameter
• Adequate renal function :glomerular filtration rate > 40 ml/min
• Clinically definite diagnosis of tuberous sclerosis (modified Gomez criteria) or sporadic LAM (biopsy-proven or compatible high resolution chest CT scan and respiratory function tests.)
• Signed and dated informed consent

Exclusion Criteria:

• History of non-compliance or inability to give informed consent
• Significant haematological or hepatic abnormality (i.e. transaminase levels > 150 i.u./L serum albumin < 30 g/L, haematocrit< 30%, platelets < 100,000/ mm3, adjusted absolute neutrophil count < 1,500/mm3, total WBC < 3,000/ mm3)
• Greater than 1 g proteinuria daily
• Multiple bilateral AMLs, where individual lesions cannot be distinguished
• Renal haemorrhage within preceding year
• In those who have had a renal haemorrhage, known conservatively managed renal aneurysm(s) greater than 10mm
• Patients who have had embolisation for AML(s) within the preceding 6 months
• Patients who are unable to walk 100 metres on the flat
• Continuous requirement for supplemental oxygen
• Patients who have had or are being considered for organ transplant
• Uncontrolled hyperlipidaemia
• Intercurrent infection at initiation of Sirolimus
• Surgery within last 2 months
• Pregnant or lactating women
• Use of an investigational drug within the last 30 days
• Change in anti epileptic drug medication within the last 3 months
• Likely to need vaccination e.g. for travel during the course of the trial (except for influenza vaccine in patients with LAM)
• Current usage of strong inhibitors of CYP3AE ( such as ketoconazole, voriconazole, itraconazole, tilithromycin or clarithromycin) or strong inducers (such as rifampicin or rifabutin)