A 60-year old male presented with discoloration, thickening, and tunneling of 2 fingernails and one toenail. Which of the following will clinch the diagnosis at the earliest?
Ans. b. KOH mount (Ref: Rook's 7/e p36.18)Discoloration, thickening, and tunneling of two fingernails and one toenail is suggestive of onychomycosis or Tinea unguum. The most important test to diagnose this is naif scraping for KOH.Tinea unguum (Onychomycosis)Tinea unguum is the ringworm of nail, usually caused by T. rubrum.It causes yellowish discoloration of the nails along with thickening of the nails.The most important test to diagnose this is a nail scraping for KOH.TypeAffected body partCausative agentTinea carporis (glabrosa)Skin of body or limbs(usually non hairy)T. verrucosumQTinea cruris (Dhobi/jack itch)Groin, perineum, thighs, scrotum (least and late involvement)Trichophyton rubrumQE. floccosumTinea capitisScalpMicrosporum canis (MC)QT. schoenleini, T. tonsuransTinea pedis (Athelete foot)Feet, MC 4th web spaceT. rubrumQT. mentagrophyte, E. floccosumTinea manuumPalmsT. rubrumQTinea unguum (Onychomycosis)Nail plate >nail bedQT. rubrumQT. mentagrophyte, E. floccosum
Wood's lamp examination
KOH mount
Slit smear (split skin smear)
Gram stain