Abstract
BACKGROUND: Hand, foot, and mouth disease (HFMD), classically a childhood viral infection, has an atypical and severe clinical presentation in adults. Coxsackievirus A6 is a leading cause of atypical HFMD, but current diagnostic methods utilizing formalin-fixed, paraffin-embedded skin biopsy specimens often lack sensitivity and specificity. METHODS: Formalin-fixed, paraffin-embedded skin biopsies from seven case patients with clinical and histopathological suspicion of atypical HFMD were evaluated by coxsackievirus A6 (CVA6) immunohistochemistry, enterovirus-specific conventional reverse transcriptase-PCR with subsequent Sanger sequencing targeting the 5'UTR, and CVA6-specific real-time PCR targeting the VP1 gene. RESULTS: The CVA6-specific antibody demonstrated appropriate antigen distribution and staining intensity in keratinocytes in all cases. Conventional RT-PCR and sequencing also detected the presence of enterovirus, and CVA6-specific real-time RT-PCR analysis identified CVA6. CONCLUSION: Applying these immunohistochemistry and molecular techniques to formalin-fixed, paraffin-embedded tissues, CVA6 was determined to be the causative infectious agent in seven cases of atypical hand, foot, and mouth disease.