Rare lung disease more prevalent than previously reported

New research conducted across four countries and led by UCD’s Dr Evelyn Lynn under the supervision of Prof Cormac McCarthy, demonstrates that the rare lung disease LAM is more prevalent than previously reported and that diagnosis is imperative.¹

Lymphangioleiomyomatosis (LAM) is a rare lung disease. It leads to the development of cysts in the lungs and predominantly impacts women during their reproductive years. The disease can be sporadic (S-LAM) or associated with the neurological condition tuberous sclerosis complex (TSC-LAM). Women with LAM experience shortness of breath, cough, pneumothorax (lung collapse), chylothorax (buildup of fluid around the lung) and some require oxygen and lung transplantation. Patients with LAM can also develop renal angioleiomyomas (AML) and leiomyomas, which are non-cancerous growths on the kidneys and in the uterus.

To achieve a diagnosis of LAM, patients need to have a CT thorax showing typical cysts plus a history of TSC, evidence of AML or leiomyomas, a chylothorax or a vascular endothelial growth factor-D (VEGF-D) level of >800 pg/ml. With effective treatment available, the research emphasises the importance for patients to be diagnosed. 

The previous reported prevalence has been 3-8 cases per million women worldwide. With improved awareness and understanding of the disease and increased access to diagnostics, more cases of LAM are being identified. The research team for this paper believes the reported prevalence to be an underestimation and that, while still rare, LAM is more common than suggested.

To investigate this, physicians from four similar-sized European countries with national health services collated data on the number of LAM patients attending their service. This included LAM experts in centres in Ireland, Denmark, Norway and the Netherlands. In total, 351 patients with LAM were identified across the four countries. The majority (66%) had sporadic LAM. The remainder (34%) had TSC-LAM. All patients were female. In Ireland, the team found the prevalence to be 26 cases per million females (Norway = 24/million, Denmark = 24/million, the Netherlands = 22/million). 

The findings differ significantly from previous reports, supporting the research team’s belief that LAM prevalence has historically been underestimated. The data suggests the prevalence is at least 21 cases/million women worldwide. 

This appears to represent improved recognition of the disease. However, many cases still remain undiagnosed. The research recommends that all females with cystic lung disease need to be assessed for LAM and referred to an appropriate centre with expertise.