Toenail fungus is one of the causes of black toenails. Besides due to fungal infection, color change can also be caused by a variety of things. Viewed from the histology, the presence of melanin on nail could be caused by both excessive activation of melanocytes or excessive growth of melanocytes. Because of the multiple mechanisms of this disorder, treatment should be done based on the cause. However, the main objective in the management of black toenail is the correct diagnosis so that appropriate treatment can be carried out.
Excessive activation of melanocytes could be due to several things. Some medications such as antiretroviral and antimalarial drugs can cause black nail. Color changes induced by these drugs usually in the form of multiple light brown to black longitudinal or transverse bands on several nails. Multiple drugs consumption can also cause nail color abnormalities.
In addition to Drug-Induced Melanonychia, inflammation can also cause the activation of melanocytes in the toenail. Toenail exposed to friction from shoes in a long time will cause a chronic inflammation. Chronic inflammation may activate the melanocytes that cause black toenail discoloration. Endocrine diseases such as Addison’s disease also causes excessive activation of melanocytes. In patients with squamous cell carcinoma, the activation of melanocytes in the nail are also commonly found.
In addition to the above conditions, toenail fungus also often causes black toenail. The fungus infects the nail can directly activate melanocytes. However, some fungi can also produce some black pigments. Common causes of toenail fungus, Trichophyton rubrum, can produce a black pigmented hyphae which causes a diffuse or banded nail pigmentation.
Malignancy involving the melanocytes can cause excessive growth of melanocytes. This excessive growth eventually led to the accumulation of melanin pigment in the nail. Some malignancies, such as Benign Melanocytic Hyperplasia, Nevus of the Nail Matrix, Melanoma, Nail Matrix Melanoma, and Nail Bed Melanoma often causes black toenail.
Correct diagnosis is needed in the handling of black toenail. Treatment will aim to tackle the causes discoloration of the nails. If the nail discoloration caused by fungus, successful antifungal therapy will also overcome the black toenail.