A 62-year-old woman treated with pranlukast for 2 months developed intersti
tial pneumonitis with a high fever. A lymphocyte stimulation test was react
ive to pranlukast. Her clinical symptoms improved with discontinuation of p
ranlukast and administration of systemic corticosteroid. To our knowledge,
this is the first reported case of drug-induced lung disease involving a le
ukotriene. The steps that can be taken to promptly reach a diagnosis and to
successfully treat this life-threatening condition are described.