Step 1: Define AIDS related complex. ARC is a symptomatic class B stage of HIV in which the weakened immune system allows various opportunistic and constitutional features to appear.
Step 2: List its features. ARC includes long-lasting diarrhea, marked weight loss, prolonged fever, night sweats, recurrent infections including genital candidiasis, generalized lymphadenopathy, oral hairy leukoplakia and herpes zoster.
Step 3: Identify the odd one. Ectopic pregnancy is an implantation of a pregnancy outside the uterine cavity and has nothing to do with the immune dysfunction of HIV. The other three are recognized ARC features, so ectopic pregnancy is the answer.