DP12 Painful oral keratosis and skin lesions: a paraneoplastic diagnostic conundrum
Authors: Finn Daniel , Harnett Clare , Azurdia Richard , Yesudian Paul 
Published: June 2023

A 70-year-old man was referred to oral medicine with extensive, painful oral hyperkeratosis affecting the tongue, buccal mucosa and palate. Medical history included a previous diagnosis of prostate cancer. Histology from multiple oral biopsy specimens showed only hyperparakeratosis and acanthosis, with no fungi or dysplasia. Owing to the absence of oral inflammation, the pain was treated as neuropathic. The patient then developed skin lesions and dermatology review was requested. Skin examination revealed marked hyperkeratotic, verrucous plaques affecting the extensor surfaces of the limbs and dorsal hands, as well as the plantar feet bilaterally. The nails were unaffected. There was violaceous discolouration of the pinnae. Given the history of prostate cancer, a paraneoplastic process was suspected. Two incisional biopsies were taken, which showed epidermal acanthosis with necrotic and dyskeratotic keratinocytes throughout the epidermis. There was a dense eosinophilic inflammatory infiltrate. Direct and indirect immunofluorescence was negative. The appearances were suggestive of a paraneoplastic phenomenon, including acrokeratosis paraneoplastica. Haematological investigations identified an IgG monoclonal paraproteinaemia with raised kappa:lambda ratio. Following further investigation, including bone marrow biopsy and positron emission tomography computed tomography, a diagnosis of monoclonal gammopathy of undetermined significance was made by haematology. A repeat bone marrow biopsy 7 months later confirmed evolution to myeloma. As CRAB criteria (hypercalcaemia, renal insufficiency, anaemia and bone lesions) were absent, a period of observation followed. A trial of oral steroids improved the cutaneous eruption, but he developed significant side-effects. Oral mycophenolate, methotrexate and acitretin were used as steroid-sparing agents, with a poor clinical response. The skin lesions progressed to a widespread psoriasiform eruption on the trunk and lower limbs with the formation of bullae. Further biopsies showed an eosinophil-rich infiltrate with negative immunofluorescence, raising the possibility of an eosinophilic dermatosis of haematological malignancy. After 2 years, given the worsening skin symptoms, it was decided to commence bortezomib, cyclophosphamide and dexamethasone (VCD) chemotherapy. Despite four cycles of VCD treatment, the skin lesions worsened and as the paraprotein levels did not reduce, treatment was stopped. Subsequently, further elevations in serum free light chains prompted treatment with lenalidomide. This resulted in a marked improvement in the skin and reduced pain from the oral lesions, as well as a reduction in serum free light chains. Acrokeratosis paraneoplastica (Bazex syndrome) is characterized by digital hyperkeratosis and paronychia, which may progress to involve the limbs and trunk. Eosinophilic dermatosis of haematological malignancy is characterized by a pruritic, papular skin eruption with a vesiculobullous component. This case presents a diagnostic conundrum, with evolving features of two different paraneoplastic conditions.