**Core Concept**
Psoriasis is a chronic inflammatory skin condition characterized by accelerated keratinocyte proliferation and impaired immune response. Certain medications can exacerbate psoriatic lesions by influencing the underlying pathophysiological mechanisms.

**Why the Correct Answer is Right**
Beta-blockers, such as propranolol, are known to exacerbate psoriasis by reducing the clearance of circulating neutrophils, leading to increased inflammation and keratinocyte proliferation. This effect is mediated through the blockade of beta-2 adrenergic receptors, which normally help regulate neutrophil function.

**Why Each Wrong Option is Incorrect**
**Option A:** Corticosteroids are actually used to treat psoriasis, not worsen it. They reduce inflammation and suppress the immune response.
**Option B:** Methotrexate is a systemic retinoid used in the treatment of severe psoriasis. It works by inhibiting dihydrofolate reductase and reducing cell proliferation.
**Option C:** Cyclosporine is an immunosuppressive agent used to treat severe psoriasis. It works by inhibiting calcineurin and reducing T-cell activation.

**Clinical Pearl / High-Yield Fact**
Beta-blockers can be a hidden cause of worsening psoriasis, especially in patients with a history of the condition. It's essential to consider this potential interaction when prescribing beta-blockers.

**Correct Answer: A. Propranolol.**