Differential Diagnosis for Toe Nail Infection
Single Most Likely Diagnosis
- Onychomycosis: This is the most common cause of toe nail infections, accounting for a significant percentage of cases. It is a fungal infection of the nail, often caused by dermatophytes, and can lead to thickening, discoloration, and brittleness of the nail.
Other Likely Diagnoses
- Bacterial Onychitis: Bacterial infections can cause nail infections, often presenting with signs of inflammation such as redness, swelling, and pus. This can be secondary to trauma or an underlying condition that compromises the nail's integrity.
- Paronychia: An infection of the skin around the nail (perionyx), paronychia can be caused by bacteria or fungi. It presents with pain, redness, and swelling around the nail and can be acute or chronic.
- Onychocryptosis (Ingrown Toenail): While not an infection per se, ingrown toenails can become infected, leading to pain, redness, and swelling. This condition occurs when the nail grows into the surrounding skin.
Do Not Miss Diagnoses
- Diabetic Foot Infection: In patients with diabetes, any foot infection, including those of the toenail, can rapidly progress to a severe, limb-threatening condition. Early recognition and treatment are crucial.
- Cellulitis: A bacterial infection of the skin and subcutaneous tissues, cellulitis can start around an infected toenail and spread. It requires prompt antibiotic treatment to prevent serious complications.
- Osteomyelitis: Bone infection can occur as a complication of a toenail infection, especially in individuals with compromised immune systems or diabetes. It is a serious condition that requires aggressive treatment.
Rare Diagnoses
- Squamous Cell Carcinoma: Though rare, long-standing nail infections or inflammation can be associated with an increased risk of squamous cell carcinoma of the nail bed.
- Melanonychia: Pigmentation of the nail can be caused by a variety of conditions, including melanoma. While rare, any new or changing pigmentation of the nail should be evaluated to rule out malignancy.
- Keratoacanthoma: A rare, low-grade malignancy that can mimic an infected toenail, keratoacanthoma typically grows rapidly and can resolve on its own but may require surgical removal for diagnosis and treatment.