What is the primary cause of melanonychia?

• A. Trauma or injury
• B. Genetic factors
• C. Increased melanin production
• D. Fungal infection

Answer: (C)

Melanonychia is characterized by brown or black discoloration of the nails and is primarily caused by increased melanin production within the nail matrix. When melanocytes, which are the cells that produce melanin, become activated or increase in number, it leads to the deposition of melanin in the nail. This can occur due to various reasons, but the primary factor remains the overproduction of melanin.

While trauma or injury can result in nail discoloration, it usually manifests as a bruise rather than melanonychia. Genetic factors can also play a role in the predisposition to certain types of melanonychia, but they are not the main cause of the condition itself. Fungal infections typically do not result in melanin production and would exhibit other symptoms characteristic of fungal elements. Thus, the increased melanin production is the definitive factor driving the condition of melanonychia.