Onychomycosis is a fungal infection of the nail, usually a toenail, most often caused by dermatophytes such as Trichophyton rubrum. It becomes more common with age, diabetes and poor circulation, and treatment takes months because nails grow slowly.
Key symptoms
- Thick, yellow, white or brown nails
- Nails that crumble, split or lift from the nail bed
- Discomfort in shoes or when walking
- Often itchy, scaly feet (athlete's foot) as well
What you find on exam
- Thick, discolored nail with debris underneath
- Nail lifting off the nail bed (onycholysis)
- Check the skin between the toes for tinea pedis
- Diabetic foot exam: pulses, sensation and breaks in the skin
Tests
- KOH prep of nail clippings and debris
- Fungal culture, PAS stain or PCR of a nail clipping
- Baseline liver tests before oral terbinafine
Treatment basics
- Confirm fungus before starting oral therapy
- Oral terbinafine 250 mg daily: 12 weeks for toenails, 6 weeks for fingernails
- Topical efinaconazole or ciclopirox for mild disease or when pills are not an option
- Trim and file nails, treat athlete's foot, keep feet dry and change socks
- Expect slow results; relapse is common
Red flags
- Diabetes or poor circulation with skin breaks, redness or ulcers
- Dark streak, or pigment spreading to the skin around the nail (rule out melanoma)
- Jaundice, dark urine or fatigue while taking terbinafine
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.