On Pap smear, koilocytic change (perinuclear halo with enlarged, raisinoid nuclei) is characteristic of infection by which organism?

• A Human papillomavirus (HPV) ✓
• B Herpes simplex virus (HSV)
• C Trichomonas vaginalis
• D Chlamydia trachomatis

Explanation

Koilocytes are squamous cells with a clear perinuclear halo (caused by cytoplasmic clearing around the virus-induced altered nucleus), an enlarged pyknotic or raisinoid nucleus, and irregular nuclear membrane — these are the cytopathic effect of HPV infection. Koilocytic change on Pap smear correlates with low-grade squamous intraepithelial lesion (LSIL/CIN 1). HSV produces multinucleated giant cells with ground-glass nuclei and Cowdry A inclusions; Trichomonas shows pear-shaped flagellated organisms; Chlamydia inclusions are not typically seen on Pap.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.