Differential Diagnosis of Painful Lesions of Nail Associated with Melanonychia
Single Most Likely Diagnosis
- Melanocytic nevus: This is a common cause of melanonychia and can sometimes be painful if the nevus is large or if there is associated nail plate distortion. The pain is usually mild and intermittent.
Other Likely Diagnoses
- Onychomycosis: Fungal infections of the nail can cause pain, especially if there is significant nail plate thickening or if the infection has led to the development of a subungual hematoma. Melanonychia can be seen in some cases of onychomycosis, particularly those caused by certain fungi that produce melanin.
- Subungual melanoma: Although less common than melanocytic nevi, subungual melanoma is a significant cause of melanonychia and can be painful, especially if the tumor is large or has ulcerated. Pain in subungual melanoma can be due to the tumor itself or due to associated nail plate changes.
- Nail trauma: Trauma to the nail can cause painful lesions and melanonychia, especially if the trauma leads to the formation of a subungual hematoma. The hematoma can appear as a melanonychia stripe.
Do Not Miss Diagnoses
- Subungual squamous cell carcinoma: This is a rare but aggressive tumor that can present with painful nail lesions and melanonychia. It is crucial to diagnose this condition early to improve prognosis.
- Subungual keratoacanthoma: Although typically benign, subungual keratoacanthoma can be painful and may mimic more serious conditions like squamous cell carcinoma. It can occasionally present with melanonychia.
- Glomus tumor: A glomus tumor is a benign but painful tumor of the nail bed that can cause melanonychia. It is usually extremely painful, especially to pressure.
Rare Diagnoses
- Subungual blue nevus: A rare cause of melanonychia, blue nevi can occasionally be painful, especially if they are large or if there is associated nail plate distortion.
- Subungual lentigo: Although typically benign and not painful, subungual lentigines can rarely cause discomfort if they lead to significant nail plate changes.
- Nail bed melanosis: This condition involves an increase in melanin in the nail bed and can cause melanonychia. It is usually not painful but can be in some cases, especially if there is associated inflammation.