A Young Man Who Is Otherwise Healthy Presents With A Sandpaperlike Rash ...

A 20-year-old man presents to your office complaining of a sandpaperlike rash that affects his upper outer arms. He is otherwise healthy and has no other symptoms. The most likely diagnosis is
A) Scarlet fever
B) Infectious mononucleosis
C) Keratosis pilaris
D) Seborrheic dermatitis
E) Psoriasis

The rash is shown in picture below:

The answer is C. (Keratosis pilaris)

Keratosis pilaris is defined as hyperkeratotic follicular papules on the extensor surface of the upper arms or upper anterior thighs and occasionally on the malar area of the face.
It may be associated with atopy and dry skin. A sandpaper-like feel is noted in these isolated areas. The condition is considered benign and is treated with topical lactic acid cream or lotion. Lesions that are associated with the face typically resolve at puberty.