Think that must just be rumour; he's just old but unfortunately tenaciously hanging on.
End stage syphilis commonly has other more unpleasant symptoms (like bits of your face falling off and other signs of physical decay) and these days most cases of syphilis can be cured with drugs; I keep reading and teaching texts (Ibsen, for one) where minor characters are revealed to suffer from it, so have become more informed than I would wish on the subject!