Clues from a rare disease shed light on how pneumonia damages the lungs.

People with a condition called Byler's disease are prone to pneumonia. They also harbour mutations in a protein called ATP8b1 that transports certain lipids across the cell membrane into cells. Rama Mallampalli of the University of Pittsburgh in Pennsylvania and his colleagues reasoned that ATP8b1 might shield the lungs from inflammation by removing cardiolipin, a lipid prevalent in injured lungs, from the airways.

The researchers found high levels of cardiolipin in the lungs of patients with pneumonia. Studies in mice showed that cardiolipin inhibits the function of alveolar surfactant, an oily substance that keeps airways open. Mice with mutated ATP8b1 had higher levels of cardiolipin in lung fluid and were more susceptible to lung damage caused by infection. The authors suggest that high cardiolipin levels overwhelm ATP8b1 transporters during infection, allowing the lipid to accumulate.

Nature Med. doi:10.1038/nm.2213 (2010)