Onychomycosis is a fungal infection of the nail caused by dermatophytes, non-dermatophyte molds, and yeasts (mainly Candida species). Incidence increases with age, and it rarely occurs in children. Dermatophytes (Trichophyton rubrum) account for 80% of toenail infections. Onychomycosis is categorized clinically as distal and lateral subungual onychomycosis (DLSO), superficial white onychomycosis (SWO), proximal subungual onychomycosis (PSO), candida onychomycosis, and total dystrophic onychomycosis. Diagnosis of onychomycosis involves physical, microscopic examination and culture. Histologic evaluation using PAS staining is a sensitive method for detecting onychomycosis. Moreover, eradication of the infection is important to improving the cosmetical appearance and avoiding complications. However, it is not simply accomplished because nails are made of hard keratin, which is avascular and resistant to many agents. Thus, creams and other topical medications are commonly not effective against nail fungus. Treatment results take up to a year to appear because nails have poor drug delivery. Treatment differs depending on the severity of nail changes, the involved organism, and adverse effects. Clinical cure refers to improvement in the nail’s appearance, often described as a normal appearance in 80% to 100% of the nail. Usually, effective treatment is achieved by systemic antifungal therapy. Antifungals from the allylamine and azole classes are the most widely used oral medications to treat onychomycosis. The azole class includes itraconazole, fluconazole, and ketoconazole; however, ketoconazole is seldom prescribed because of hepatotoxicity and drug interactions. Itraconazole is prescribed in “pulse doses” one week per month for 2 or 3 months. It can interact with erythromycin or asthma medications. Furthermore, itraconazole’s most frequent side effects include gastrointestinal side effects, transaminitis, high lipids, and skin rash. The allylamine class is represented by terbinafine. Terbinafine is taken daily for eight weeks for fingernail fungus and 12 weeks for toenail fungus. The most frequent side effects are gastrointestinal disturbance, headache, and transaminitis.

Written By: Dr. Fatimah Alowirdi, Dermatology Resident

References:

https://dermnetnz.org/topics/fungal-nail-infections/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC88888/