What to Know about Melanonychia
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Try for freeThis post was written with Consensus AI Academic Search Engine – please read our Disclaimer at the end of this article. Melanonychia is a complex condition with a wide range of causes. Accurate diagnosis and appropriate management are crucial to prevent misdiagnosis and ensure effective treatment. Clinicians should be aware of the various etiologies and use a systematic approach to evaluate and manage this condition.
Melanonychia refers to the brown or black pigmentation of the nail plate, which can be caused by a variety of factors. This condition can be a diagnostic challenge for clinicians due to its diverse etiologies, ranging from benign to malignant causes. Understanding the underlying causes, diagnostic methods, and treatment options is crucial for effective management.
Causes of Melanonychia
Melanonychia can be caused by both exogenous and endogenous factors. Exogenous sources include bacterial or fungal infections, tar, or blood2. Endogenous causes are often related to melanin production in the nail bed, which can result from melanocytic activation or hyperplasia3.
Fungal Melanonychia
Fungal melanonychia is a relatively rare condition caused by nail infections that produce brown-to-black pigmentation. Over 21 species of dematiaceous fungi and at least 8 species of nondematiaceous fungi have been implicated as etiologic agents1. Common fungi include Candida and Aspergillus species6. These infections can mimic subungual melanoma and are often resistant to traditional antifungal therapies1 6.
Melanocytic Lesions
Melanonychia can also result from melanocytic lesions, which may be benign or malignant. Benign causes include nail matrix melanocytic activation and hyperplasia, while malignant causes include melanoma3. In children, benign melanocytic hyperplasia such as lentigo or nevus is a common cause7 9.
Drug-Induced Melanonychia
Certain medications can induce melanonychia, affecting multiple nails and presenting as light brown to black pigmentation. Chemotherapeutic agents like azathioprine, bleomycin sulfate, and methotrexate are commonly associated with this condition. A case of melanonychia induced by the traditional Chinese herb Citri reticulatae pericarpium has also been reported10.
Diagnostic Methods
Accurate diagnosis of melanonychia is essential to differentiate between benign and malignant causes. Diagnostic tools include dermoscopy, biopsy, and histopathologic examination4 5.
Dermoscopy
Dermoscopy is routinely used to evaluate pigmented nails. It helps identify whether the pigmentation is due to melanocytic activation or proliferation4.
Biopsy and Histopathology
When melanocytic proliferation is suspected, a biopsy followed by histopathologic examination is the gold standard for diagnosis. This is particularly recommended for longitudinal melanonychia in adults localized to a single digit4. Histopathologic features such as melanocyte counts and the presence of suprabasal melanocytes are crucial for diagnosis9.
Management and Treatment
The management of melanonychia depends on the underlying cause.
Malignant Lesions
Malignant lesions, such as melanoma, require excisional biopsy and appropriate oncologic treatment2 5.
Fungal Infections
Fungal melanonychia should be treated with antifungal agents. However, these infections can be persistent and may recur after treatment cessation6.
Benign Lesions
Benign lesions and hyperpigmentation may be managed conservatively with a wait-and-see approach. Regular monitoring is essential to detect any changes that may indicate malignancy2 9.
Disclaimer
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