expression, godan verb (-mu)
suffer from tuberculosis
A somewhat literary or old-fashioned expression for having tuberculosis. In modern conversation, 結核にかかる or 肺結核になる is more common.
彼は若い頃に肺を病んで、長く療養所で過ごした。
He suffered from tuberculosis when he was young and spent a long time in a sanatorium.
結核 is the modern medical term for tuberculosis. 肺を病む is a more literary, indirect way of saying someone has the disease.
Compound of 肺 (lung) + を (object marker) + 病む (to be ill). The exact historical origin is uncertain, but it has been used as a set phrase for tuberculosis since at least the early 20th century.