Carlos Ghosn's "illegal" arrest has interrupted his care for chronic kidney failure, which the former Nissan Motor boss suffers from as a result of treatment for high cholesterol, his defence said in documents seen by Reuters on Thursday. The news came as Japanese authorities questioned his wife Carole at a closed-door hearing the same day, his lawyer said. Mrs Ghosn has increasingly emerged as a key figure in the case surrounding her tycoon husband, who is in detention facing multiple allegations of financial malpractice, according to AFP. Mr Ghosn's lead defence lawyer Junichiro Hironaka confirmed to reporters that Mrs Ghosn had answered authorities' questions but would not be drawn on the detail of the ongoing investigation. "She responded in good faith as she had promised to," he said, but declined to offer specifics of what was discussed during the nearly three-hour session. Japanese authorities are investigating claims that Mr Ghosn siphoned off around $5 million of Nissan funds for his personal use. Prosecutors believe this money was taken from around $15m transferred from Nissan to a dealership in the Middle East between 2015 and 2018. According to a source, some of the $5m was funnelled to a British Virgin Islands-listed company - which has Carole Ghosn registered as president - to purchase a luxury yacht.