CPC08 Acrodermatitis enteropathica in adulthood secondary to acquired zinc deficiency: a diagnostic challenge

Abstract A 76-year-old woman was initially admitted for dizziness and progressive hand tremors. She incidentally presented with a 3-week history of an annular eczematous eruption, primarily affecting her arms, legs and buttock, but sparing the face. The rash was well demarcated and erythematous and had peripheral scaling, resembling psoriasis. She had a background history of psoriasis, eczema, epilepsy, ischaemic heart disease and previous alcohol excess. Her psoriasis had previously been treated with topical coal tar and remained stable afterwards. The differential diagnosis included subacute cutaneous lupus erythematosus (SCLE), psoriasis, tinea, drug reaction and paraneoplastic conditions. Initially, the rash showed some improvement with topical corticosteroids but it flared upon discontinuation. A computed tomography scan of the thorax, abdomen and pelvis ruled out any paraneoplastic cause. Magnetic resonance imaging of the brain revealed only alcohol-related cerebellar degenerative changes, and her routine biochemical blood tests were unremarkable. Skin scrapings were negative for fungal elements. A skin biopsy revealed hyperkeratosis, acanthosis and moderate spongiosis, suggesting a spongiotic dermatitis. The patient was treated for psoriasis with ustekinumab; however, this worsened her existing rash, with the skin lesions taking on an annular, polycyclic appearance with desquamation. She was treated with potent topical corticosteroids, which improved her symptoms but failed to resolve the rash completely. This change prompted a reconsideration of the diagnosis, and differentials included SCLE, tinea, pityriasis rubra pilaris, necrolytic migratory erythema and acrodermatitis enteropathica. Two months later, a second skin biopsy was performed, revealing hyperkeratosis, parakeratosis, interface dermatitis and a perivascular inflammatory infiltrate in the superficial dermis. Periodic acid–Schiff stain was negative for fungal organisms. Further blood tests showed a normal glucagon level; however, her zinc levels were deficient at 4.4 μmol L−1 (normal range 11–18 μmol L−1). Given her history of alcohol excess and acquired nutritional deficiency, a diagnosis of acrodermatitis enteropathica was made. Her ustekinumab was stopped, and she was commenced on high-dose zinc supplementation 50 mg three times daily. Within 4 weeks the patient showed significant improvement in her skin lesions with 90% clearance. We present a case of acrodermatitis enteropathica in an adult patient with acquired zinc deficiency masking as psoriasis. This case highlights an important differential to consider in patients with suspected psoriasis not responding to conventional treatments.