http://www.ncbi.nlm.nih.gov/pubmed/16341329
While some of Hitler's health problems could be symptoms of syphilis there are other explanations. Apparently none of his various medical examinations detected the STD.
Also, as powerful as Hitler was he could have scrounged up some penicillin . . . from captured Allied supplies if nothing else. SOMEONE in his entourage could have made points with the brownshirted boss thereby.