A case of necrotizing cellulitis of the penis is reported. In this pat
ient, transient functional protein S deficiency during the infectious
process was demonstrated with a marked decrease of free protein S and
elevated C4b-binding protein levels. Moreover, by investigating other
members of this patient's family it was possible to demonstrate a subc
linical inherited protein S deficiency. In this study it is suggested
that the profound and transient decrease of functional protein S obser
ved in this patient during infectious cellulitis, may have contributed
to the pathogenesis of tissue necrosis.