Onychomycosis: Diagnosis and Systemic Treatment

Overview / Definition Onychomycosis, or nail fungus, is defined as a fungal infection that affects the keratin of the nail unit, primarily the toenails but can also involve fingernails. It is characterized by nail discoloration, thickening, and possible separation from the nail bed, which can lead to pain and secondary infections. Epidemiology Onychomycosis is a prevalent condition, affecting approximately 2-14% of the general population, with higher rates observed in older adults. Factors contributing to the increased prevalence include age, diabetes mellitus, immunosuppression, and a history of tinea pedis. Prevalence: 2-14% in the general population Age factor: More common in older adults Risk factors: Diabetes, immunosuppression, tinea pedis Pathophysiology / Mechanism The pathogenesis of onychomycosis involves the invasion of the nail matrix and bed by fungi, primarily dermatophytes (e.g., Trichophyton rubrum, Trichophyton mentagrophytes), yeasts (e.g., Candida albicans), and non-dermatophyte molds. These organisms thrive in warm, moist environments, leading to keratin degradation and subsequent nail changes. The infection often begins distally and progresses proximally. Clinical Presentation Clinically, onychomycosis presents with a variety of signs: Distal subungual onychomycosis (DSO): Most common form; characterized by yellow-brown discoloration and nail thickening. White superficial onychomycosis (WSO): Presents as white spots on the nail surface. Proximal subungual onychomycosis (PSO): Involves the proximal nail fold, more common in immunocompromised patients. Candida onychomycosis: Often affects fingernails, leading to nail lifting and inflammation. Diagnosis / Workup Diagnosis of onychomycosis involves: Clinical examination: Assessing nail appearance and associated symptoms. Laboratory testing: Nail clipping for potassium hydroxide (KOH) preparation and culture to identify the organism. Histopathology: Nail biopsy may be required in atypical cases. Derm