Detecting acute HIV infection is important, but often the infection is difficult to recognize. We report the case of a 23-year-old man with persistent genital ulceration; all microbiological examinations from the ulcers were negative. HIV-1/2 antibodies were positive, but the HIV-1 Western blot (WB) was indeterminate and HIV-1 p24 antigen was persistently negative, with a low HIV-1 RNA level. One month later, the genital ulcerations disappeared and the WB test showed complete seroconversion; nonetheless HIV p24 antigen remained negative and HIV-RNA was persistently low. HIV-1 proviral DNA was detected by nested polymerase chain reaction (PCR) from the initial ulcers swabs. This case was notable due to genital ulceration being the only sign of primary HIV infection. Furthermore, the serological pattern was unusual, and HIV-RNA was unexpectedly low. This underlines the importance of screening for HIV being infection in the setting of sexually transmitted infections (STIs), and also in cases of atypical STI-like presentations.