This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: S.T.D., Subject name: Skin
Homosexual man with pain in defecation, no gastrointestinal symptoms, clustered ulcers extending into anal canal. Diagnosis - 
Select and explain. 
A. CMV, B. Gonorrhea, C. Herpesgenitalis, D. HIV
C: Herpesgenitalis
Answer: C: Herpesgenitalis 
Explanation: Ans. is 'c' i.e., Herpes genitalis o Herpes genitalis is a sexually transmitted disease, characterized by appearance of multiple painful vesicles in clusteres in genital area which later on may ulcerate. These small ulcers may combine to form a large ulcer. First attack of this in infection may be associated with flu like symptoms but GIT symptoms are usually absent,o Gonorrhea is characterized by acute anterior arthritis associated with thick yellow urethral discharge. Perianal ulceration is not a feature of gonorrhea.o Although HIV can be considered in the differential diagnosis of Perianal ulcers, but is usually associated with GIT symptoms.o Perianal ulceration is not a feature of CMV infection.