Differential Diagnosis for 20-year-old Female with Recent Trip to Fiji

Single Most Likely Diagnosis

• Onychomadesis due to fungal infection: This condition, characterized by the separation and falling off of nails from the nail bed, can be triggered by a fungal infection, which is common in tropical regions like Fiji. The recent travel history and the preceding skin infection on the shin support this diagnosis.

Other Likely Diagnoses

• Paronychia: An infection of the nail fold, which could have led to the nail falling off. Given the patient's history of a shin infection, it's plausible that a similar infection occurred in the nail fold.
• Onychomycosis: A fungal infection of the nail itself, which could cause the nail to become brittle and fall off. This is a common condition that can be exacerbated by travel to warm, humid climates.
• Trauma: Physical trauma to the nail can cause it to fall off. Although not directly mentioned, it's possible that some form of trauma occurred during the trip.

Do Not Miss Diagnoses

• Sepsis or systemic infection: Although less likely, if the patient's nail condition is part of a larger systemic infection, it could be life-threatening. The history of a recent infection on the shin necessitates consideration of this possibility.
• Autoimmune disorders (e.g., alopecia areata, psoriasis): These conditions can cause nail loss among other symptoms. While less common, they are critical to diagnose due to their systemic implications.

Rare Diagnoses

• Leptospirosis: A bacterial infection that can be contracted through water exposure, which might fit with travel to Fiji. It can cause a wide range of symptoms, including skin and nail changes, though it's less commonly associated with nail loss.
• Diphtheria: A bacterial infection that, in rare cases, can cause skin and nail lesions. Given the travel history, it's a remote possibility but should be considered in the differential due to its severity.