Pityriasis alba may be a manifestation of
**Core Concept**
Pityriasis alba is a common, benign skin condition characterized by patches of hypopigmentation with a fine scale, typically seen in children and adolescents. It is often associated with atopic dermatitis and is thought to result from an impaired skin barrier function and altered ceramide metabolism.
**Why the Correct Answer is Right**
The correct answer is atopic dermatitis. Atopic dermatitis, also known as eczema, is a chronic inflammatory skin condition that is often associated with a family history of atopy. Individuals with atopic dermatitis have an impaired skin barrier function, leading to increased permeability and water loss, which can cause dryness, scaling, and hypopigmentation. Pityriasis alba is thought to be a variant of atopic dermatitis that presents with more subtle symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** Psoriasis is a chronic autoimmune skin condition characterized by thick, scaly plaques, which is distinct from the fine scaling and hypopigmentation seen in pityriasis alba.
**Option B:** Contact dermatitis is a type of skin inflammation caused by exposure to an allergen or irritant, which typically presents with a more acute onset and a clear inciting factor, rather than the chronic, asymptomatic nature of pityriasis alba.
**Option C:** Seborrheic dermatitis is a chronic inflammatory skin condition that presents with a yellow, oily crusting and scaling, particularly on the scalp, face, and torso, which is distinct from the fine scaling and hypopigmentation seen in pityriasis alba.
**Clinical Pearl / High-Yield Fact**
Pityriasis alba is often seen in children and adolescents with a history of atopic dermatitis, and its presence may indicate an increased risk of developing other atopic conditions, such as asthma or allergic rhinitis.
**Correct Answer:** D. Atopic dermatitis.