To the Editor:
We read with interest the article by Chang et al. [1], which demonstrated doxycycline to have no effect on pulmonary function tests (PFTs) and is unlikely to have a potential benefit in lymphangioleiomyomatosis (LAM). An increase in metalloproteinases (MMPs) is considered one of the pathways involved in the pathogenesis of cystic lung destruction in LAM. As a result, doxycycline, a MMP inhibitor, may represent a potential therapeutic target [2–6].
One factor that could have determined a lack of effect on PFTs in the present study was that patients with LAM, treated with doxycycline, had moderate impairment in PFTs when compared with those receiving placebo, which had mild impairment. A recent nonrandomised study from our group has already suggested that patients who would most benefit with doxycycline are those with mild functional impairment [ …