Long-standing severe psoriasis with UV exposure increases risk of developing which cancer?

Long-standing severe psoriasis with UV exposure increases risk of developing which cancer?

• A. Squamous cell carcinoma
• B. Basal cell carcinoma
• C. Melanoma
• D. Kaposi sarcoma

Answer: (A)

The key idea is that phototherapy for longstanding psoriasis, especially PUVA (psoralen plus UVA), increases the risk of skin cancers from chronic UV-induced damage. UV light damages DNA in skin cells, and when psoralen sensitizes the cells to UVA, it enhances DNA crosslinking and mutations. Over years of therapy in sun-exposed skin, keratinocytes acquire mutations that can lead to squamous cell carcinoma. Basal cell carcinoma and melanoma are also linked to UV exposure, but PUVA-associated cancer risk is strongest for squamous cell carcinoma. Kaposi sarcoma arises from HHV-8 infection in the context of immunosuppression, not UV therapy. So the cancer most associated with long-standing psoriasis treated with UV exposure is squamous cell carcinoma.

The key idea is that phototherapy for longstanding psoriasis, especially PUVA (psoralen plus UVA), increases the risk of skin cancers from chronic UV-induced damage. UV light damages DNA in skin cells, and when psoralen sensitizes the cells to UVA, it enhances DNA crosslinking and mutations. Over years of therapy in sun-exposed skin, keratinocytes acquire mutations that can lead to squamous cell carcinoma. Basal cell carcinoma and melanoma are also linked to UV exposure, but PUVA-associated cancer risk is strongest for squamous cell carcinoma. Kaposi sarcoma arises from HHV-8 infection in the context of immunosuppression, not UV therapy. So the cancer most associated with long-standing psoriasis treated with UV exposure is squamous cell carcinoma.