CPC10 An unusual case of bilateral periorbital lesions
Authors: Adiotomre Moira , Simpson Rosalind , Bishton Mark , Elsheikh Somaia 
Published: June 2023

Abstract
A 45-year-old man was referred to the dermatology department for a 5–10-year history of enlarging periorbital xanthelasma-like lesions with a non-significant lipid profile. The periorbital lesions episodically and spontaneously became swollen and were associated with a throbbing sensation. After exercise and minimal motion, haemorrhage into the lesions occurred. Clinical examination revealed multiple coalescing, symmetrical, thick, yellow plaques and nodules with red–brown areas of discoloration associated with eyelid telangiectasia. His past medical history included hiatus hernia, lipoma and Osgood-Schlatter disease of the knee. The differential diagnosis included adult-onset xanthelasma, necrobiotic xanthogranuloma and amyloidosis. Punch biopsy of the lesions showed histological features consistent with a xanthogranuloma. Owing to the association of this entity with underlying haematological malignancy, computed tomography was performed, which revealed a subtle 33 × 70 mm low-attenuating mass within the posterolateral aspect of the right iliacus muscle. On further radiological investigation, including magnetic resonance imaging (MRI) and positron emission tomography, an avid, nonaggressive right iliac bone lesion and nonavid bilateral, symmetrical metaphyseal and diaphyseal sclerosis involving both distal femur and proximal tibia were seen. Previous MRI of his knee, performed 3 years earlier following a fall, was reviewed and found to show an incidental signal abnormality in his distal femur. Tissue from the periocular xanthogranuloma was positive for the BRAF V600E mutation and tissue from biopsy of the right iliac crest was consistent with focal osteosclerosis. Owing to the histopathological, clinical and radiological features, a diagnosis of Erdheim–Chester disease (ECD) was established. As a result, the haematology team initiated the patient on a reducing dose of oral prednisolone with long-term methotrexate (15 mg weekly). This led to an improvement in appearance of the periorbital lesions. The differential diagnosis for periocular xanthogranuloma includes adult-onset xanthogranulomas and adult-onset asthma with periocular xanthogranuloma, necrobiotic xanthogranuloma and ECD. ECD is a rare form of non-Langerhans cell histiocytosis that is highly associated with BRAF V600E and other mitogen-activated protein kinase pathway mutations (Diamond EL, Durham BH, Haroche J et al. Diverse and targetable kinase alterations drive histiocytic neoplasms. Cancer Discov 2016; 6:154–65). The clinical course of ECD is generally aggressive, but it can vary from indolent disease to fatal multiorgan failure. Although ECD can have multiorgan involvement, approximately 25% of these patients have cutaneous manifestations (Kobic A, Shah KK, Schmitt AR et al. Erdheim-Chester disease: expanding the spectrum of cutaneous manifestations. Br J Dermatol 2020; 182:405–9). This case highlights the importance of considering ECD when faced with atypical periorbital lesions as these lesions can mimic common benign xanthelasma.