Differential Diagnosis for a Blister or Wart Along the Nail Pedicle

Single Most Likely Diagnosis

• Verruca (Wart): This is the most likely diagnosis due to the description of the lesion resembling a wart and its location around the nail pedicle. Warts are common and can occur anywhere on the skin, including around the nails.

Other Likely Diagnoses

• Herpetic Whitlow: A viral infection caused by herpes simplex virus, leading to painful blisters around the fingernails or toenails. The description of a blister that won't pop could fit this condition, especially if it's painful.
• Paronychia: An infection of the skin around the nail, which can cause redness, swelling, and sometimes a blister-like appearance. It's a common condition that could fit the description given.
• Mycotic Infection (Fungal Infection): Fungal infections around the nail can cause a variety of symptoms, including blisters. However, they are more commonly associated with changes in the nail itself, such as thickening or discoloration.

Do Not Miss Diagnoses

• Squamous Cell Carcinoma (SCC): Although rare, SCC can present as a non-healing ulcer or blister, especially in sun-exposed areas or around the nail. It's crucial to consider this diagnosis to ensure timely treatment if present.
• Melanoma: A blister or wart-like lesion that is pigmented or has irregular pigmentation could be a sign of melanoma, especially if it's new or changing. Early detection is critical for treatment outcomes.

Rare Diagnoses

• Keratoacanthoma: A rare, low-grade malignancy that can resemble a wart or a blister. It typically grows quickly and can resolve on its own, but it may require surgical removal.
• Nail Apparatus Tumor (e.g., Onychomatricoma): A rare tumor originating from the nail matrix. It can cause a variety of nail changes, including the appearance of a blister or wart around the nail.
• Epidermoid Cyst: A benign cyst that can appear as a blister-like lesion. It's less common around the nail but could be considered in the differential diagnosis.

Each of these diagnoses has a different approach to management and treatment, ranging from observation and topical treatments for benign conditions to surgical intervention and possibly chemotherapy or radiation for malignant ones. A definitive diagnosis often requires a clinical examination and possibly a biopsy.