This article is from the the official alt.spleen FAQ, by Andrew Stellman with numerous contributions by others.
Andrew says: NOTE: PLEASE DO NOT SEND ANY MAIL TO ME REQUESTING MEDICAL ADVICE! I AM NOT A DOCTOR, AND WILL NOT GIVE YOU ANY USEFUL INFORMATION.
Yes. Artist Matt Egan (firstname.lastname@example.org) once related a story told to him by a relative, about somebody who contracted mononucleosis, tripped, fell against a coffee table, ruptured his spleen, and died. The actual cause of death was severe depression at the realization that he ruptured his spleen.