**Abstract**

Onychomycosis is a common fungal infection affecting nails. The infection is frequently due to dermatophyte, while yeast and non-dermatophyte molds (NDMs) attributed especially in immunocompromised patients. NDMs and *Candida* species can be involved as primary or secondary pathogens. Candida onychomycosis (CO), most commonly caused by *C. albicans* and *C. parapsilosis*, is frequently associated with local or systemic immune disturbances. In the cases that the host immunity is severely affected, *Candida* acts as primary pathogen, while other diseases e.g., diabetes mellitus, malnutrition, and smoking serve as predisposing factors for Candida to cause secondary infection. Furthermore, formation of biofilms and production of enzymes contribute as the virulence factors of the yeasts. Clinical manifestation of CO varies, from discoloration and marked thickening of the nail to dystrophic nails with fingernails more commonly affected. Paronychia is the most common type of CO and Candida granuloma is one of the severe types of CO which often occurs in chronic mucocutaneous candidiasis. Establishing the diagnosis of CO is crucial as well as the identification of each predisposing factors. Microscopic examination and fungal cultures are the gold standard examination for diagnosing onychomycosis, while for NDM, multiple confirmation and repeated examination is needed due to its as contaminants.

**Keywords:** candida onychomycosis, nail, fungal infection, diagnostic challenges, treatment
