A patient presents with a chronic pruritic skin lesion, as depicted in the image. Which of the following is the most likely diagnosis?

Explanation

## Image Findings * **Erythematous patch:** The lesion shows significant redness. * **Ill-defined borders:** The edges of the lesion blend gradually into the surrounding normal skin. * **Scaling/Dryness:** There is evidence of superficial flaking or dryness within the patch. * **Excoriations:** Linear scratch marks are visible, indicating intense pruritus. * **Located on hairy skin:** The presence of hair suggests a common site for eczema, such as the scalp or limbs. ## Diagnosis **Key Point:** The image displays an erythematous, ill-defined patch with scaling and excoriations, which are classic features of **Atopic dermatitis** (eczema). Atopic dermatitis is a chronic inflammatory skin condition characterized by intense pruritus, xerosis (dry skin), and eczematous lesions. The morphology varies with age and chronicity, often presenting as erythematous, scaly patches or plaques, especially in flexural areas in older children and adults. Excoriations are common due to the severe itching. ## Differential Diagnosis | Feature | Atopic Dermatitis | Psoriasis Vulgaris | Tinea Corporis | Lichen Planus | | :---------------- | :---------------------------------------------- | :------------------------------------------------ | :---------------------------------------------- | :----------------------------------------------- | | **Appearance** | Erythematous, ill-defined, scaly, excoriated | Well-demarcated, erythematous plaques with silvery scales | Annular, active border, central clearing, scaly | Pruritic, Purple, Polygonal, Planar Papules/Plaques | | **Borders** | Ill-defined | Well-demarcated | Active, raised border | Distinct, often angular | | **Scaling** | Fine, sometimes greasy | Thick, silvery, micaceous | Fine, peripheral | Minimal, sometimes hyperkeratotic | | **Pruritus** | Intense | Variable, often mild | Variable | Intense | ## Clinical Relevance **Clinical Pearl:** Atopic dermatitis is part of the 'atopic triad' (asthma, allergic rhinitis, atopic dermatitis). It often has a genetic predisposition and is exacerbated by environmental triggers. ## High-Yield for NEET PG **High-Yield:** The hallmark of atopic dermatitis is **pruritus**, often described as 'the itch that rashes'. Chronic scratching leads to lichenification and excoriations. **Key Point:** Management involves emollients, topical corticosteroids, calcineurin inhibitors, and addressing triggers. Newer biologics (e.g., dupilumab) are used for severe cases. ## Common Traps **Warning:** Distinguishing chronic eczema from psoriasis can be tricky. Look for the sharp demarcation and silvery scales of psoriasis versus the ill-defined, often more excoriated appearance of eczema. ## Reference [cite:Robbins Basic Pathology, 10th Ed, Ch 24; Fitzpatrick's Dermatology in General Medicine, 9th Ed, Ch 16]