Question
A 10 years old boy developed multiple vesicles over the lips and buccal mucosa scraping taken from the lesion demonstrated presence of multiple giant cells (Tzanck cells) What is the most probable diagnosis Discuss the pathogenesis of the above condition in detail How do you diagnose this infection in laboratory Name four other viruses belonging to the same family What are the other clinical manifestation produced by this virus (1+2+3+2+2)
Answer
Most probable diagnosis: Primary herpetic gingivostomatitis, caused by Herpes Simplex Virus type 1 (HSV-1) — multiple vesicles over the lips and buccal mucosa in a child, with Tzanck smear showing multinucleated giant cells, is classical.
Pathogenesis HSV-1 is transmitted by direct contact with infected oral secretions/lesions. Primary infection occurs at the oral/oropharyngeal mucosa, where the virus replicates in epithelial cells, causing vesicle/ulcer formation and a local inflammatory response (fever, painful oral lesions, lymphadenopathy in primary gingivostomatitis). The virus then travels along sensory nerve fibres to establish lifelong latency in the trigeminal ganglion. Periodic reactivation (triggered by stress, fever, UV exposure, immunosuppression) causes recurrent lesions (“cold sores”) at or near the original site, along the distribution of the sensory nerve — the virus travels anterogradely down the nerve to the periphery during each reactivation episode.
Laboratory diagnosis
- Tzanck smear — cytological examination of vesicle base scraping showing multinucleated giant cells with intranuclear inclusions (Cowdry type A bodies); rapid but non-specific (cannot distinguish HSV from VZV).
- Viral culture — from vesicle fluid, showing characteristic cytopathic effect.
- Direct fluorescent antibody test — on vesicle scraping.
- PCR — the most sensitive/specific method, particularly important for CSF testing in suspected HSV encephalitis.
Four other viruses in the same family (Herpesviridae):
- Varicella-Zoster Virus (VZV/HHV-3).
- Epstein-Barr virus (EBV/HHV-4).
- Cytomegalovirus (CMV/HHV-5).
- Herpes Simplex Virus type 2 (HSV-2). (Others: HHV-6, HHV-7, HHV-8.)
Other clinical manifestations produced by HSV-1:
- Herpes labialis (recurrent cold sores) — the most common recurrent manifestation.
- Herpetic whitlow — finger infection, an occupational risk for healthcare workers.
- HSV keratitis — a leading infectious cause of corneal blindness in some regions.
- HSV encephalitis — a serious, potentially fatal complication with a predilection for the temporal lobes, requiring urgent empirical acyclovir treatment.