Acquired Ichthyosis — SCE Dermatology MCQ

Correct answer: C — Lymphoma (particularly Hodgkin lymphoma) and other internal malignancy

The correct answer is C, lymphoma (particularly Hodgkin lymphoma) and other internal malignancy. New onset generalised ichthyosis in an adult with no prior history of dry skin is a recognised paraneoplastic cutaneous marker, most classically linked to Hodgkin lymphoma but also reported with non-Hodgkin lymphoma and other solid tumours. The key discriminator in this stem is the acquired nature of the ichthyosis over months in a previously unaffected 60 year old, which differs entirely from the lifelong inherited ichthyoses of childhood onset. Because the skin change can precede overt lymphoma by weeks to months, its recognition should prompt urgent staging investigations (full blood count, chest X-ray or CT, lymph node assessment) rather than routine endocrine or nutritional work-up alone. Why the other options are wrong: A. Hypothyroidism only: Hypothyroidism causes a dry, coarse skin but this is a recognised minor association, not the urgent life-threatening diagnosis that must be actively excluded, and labelling it as the sole cause would miss the malignancy risk. E. Iron deficiency: Iron deficiency classically causes koilonychia, glossitis and pruritus rather than a generalised ichthyotic scale, and is not the paraneoplastic association being tested here. D. Vitamin D deficiency: Vitamin D deficiency principally affects bone health (osteomalacia, rickets) and is not a recognised cause of acquired ichthyosis. B. Diabetes only: Diabetes is associated with skin changes such as necrobiosis lipoidica and infections, but not classically with generalised acquired ichthyosis, and again framing it as the sole answer ignores the malignancy imperative. Key point: Adult onset acquired ichthyosis with no childhood history is a paraneoplastic red flag that mandates urgent exclusion of lymphoma (especially Hodgkin lymphoma) and other internal malignancy.

Reference: PCDS (Primary Care Dermatology Society), Paraneoplastic Dermatoses clinical guidance, https://www.pcds.org.uk/clinical-guidance/paraneoplastic-syndromes