expression
under the pretext of illness; using illness as an excuse
Fixed expression meaning to use illness as a pretext for avoiding something or doing something else. Often implies the illness is exaggerated or not the real reason.
彼は病気に託けて会議を欠席した。
He skipped the meeting under the pretext of being ill.
病気に託けて仕事を休むのはよくない。
It's not good to take time off work using illness as an excuse.