Which of the following is NOT a sign of nail psoriasis?

• A. Discoloration
• B. Roughness on nail surface
• C. Severe nail pitting
• D. Infectious disease

Answer: (D)

The correct answer, indicating that "infectious disease" is not a sign of nail psoriasis, highlights the fact that nail psoriasis is a specific condition related to inflammation and immune response rather than an infectious process. Nail psoriasis is primarily characterized by signs such as discoloration, roughness on the nail surface, and severe nail pitting, which are all manifestations of the underlying autoimmune disorder.

Discoloration frequently occurs in nails affected by psoriasis, resulting in an appearance that may involve yellow or reddish hues. Roughness on the nail surface reflects the structural changes that happen due to the inflammation caused by psoriasis. Severe nail pitting, which involves small depressions in the nail plate, is a classic sign that indicates the disease's impact on keratin production and nail structure.

In contrast, an infectious disease typically stems from pathogens such as bacteria, viruses, or fungi, and would present with different symptoms, like redness, swelling, and possible pus, which are not indicative of psoriasis. By recognizing that infectious diseases have distinct clinical features, it becomes clear why "infectious disease" does not fit within the spectrum of signs associated with nail psoriasis.