dermatologic disorders
Onychomycosis
Diagnosis
Clinical evaluation Potassium hydroxide wet mount examination Culture or polymerase chain reaction (PCR) Histopathologic examination of periodic acid-Schiff (PAS)–stained nail clippings and subungual debris (See also anupdateon the current approaches to diagnosis and treatment of onychomycosis.) Onychomycosis is suspected by appearance in patients who also have Tinea Pedis (Athlete's Foot) ; predictive clinical features include involvement of the 3rd or 5th toenail, involvement of the 1st and 5th toenails on the same foot, and unilateral nail deformity. Subclinical onychomycosis should be considered in patients with recurrent tinea pedis. Differentiation from Psoriasis or Obtaining an adequate sample of nail for culture can be difficult because the distal subungual debris, which is easy to sample, often does not contain living fungus. Therefore, removing the distal portion of the nail with clippers before sampling or using a small curette to reach more proximally beneath the nail increases the yield. 1.Joyce A, Gupta AK, Koenig L, et al: Fungal Diversity and Onychomycosis: An analysis of 8,816 toenail samples using quantitative PCR and next-generation sequencing.J Am Podiatr Med Assoc109(1):57–63, 2019. doi: 10.7547/17-070 2.Haghani I, Shams-Ghahfarokhi M, Dalimi Asl A, et al: Molecular identification and antifungal susceptibility of clinical fungal isolates from onychomycosis (uncommon and emerging species).Mycoses62(2):128–143, 2019. doi: 10.1111/myc.12854 3.Gupta AK, Mays RR, Versteeg SG, et al: Update on current approaches to diagnosis and treatment of onychomycosis.Expert Rev Anti Infect Ther16(12):929–938, 2018. doi: 10.1080/14787210.2018.1544891 