A patient had seven irregular hyperpigmented macules on the trunk and multiple small hyperpigmented macules in the axillae and groins since early childhood. There were no other skin lesions. Which is the most likely investigation to suppo the diagnosis?

The herpes viruses are classified into 3 families: a, b, and g. HSV-1 is the first member of the human herpes viruses belonging to the subfamily Alphaherpesvirinae. Herpes simplex keratitis is caused by HSV-1 infection of the corneal epithelium and stroma. Epithelial keratitis accounts for 70% to 80% of all cases. Dendritic epithelial keratitis, a branching pattern of epithelial infection and erosion, is the typical configuration of HSV epithelial keratitis Geographic epithelial keratitis is a less common, macro-ulcerative form of HSV corneal epithelial infection HSV stromal keratitis accounts for 2% of initial HSV-1 ocular presentations but it is the cause of 20%-61% of recurrent disease. After the primary infection, HSV typically becomes quiescent or latent in the trigeminal ganglion. Recurrent ocular HSV-1 infection and inflammation may eventually cause corneal scarring, thinning, neovascularization, and stromal keratitis. This can be absorbed in slit lamp examination of eye