BG09 A case of giant variant acquired reactive perforating collagenosis in a 94-year-old man with poorly controlled diabetes
Authors: Ashcroft Samuel , Watts Sophia , Sheraz Adil 
Published: June 2024

Abstract
A 94-year-old man was seen in the emergency clinic following the onset of a pruritic, slightly painful rash across the flanks and arms bilaterally. He had recently complained of generalized pruritis, and had been scratching aggressively. His past medical history was relevant for poorly controlled type 2 diabetes mellitus, previous renal cell carcinoma (treated with nephrectomy) and eczema. He was severely frail, with a clinical frailty score of 7, dependent for all activities of daily living. The lesions started as discrete round red patches, which became pustular and then nodular with a striking bright red violaceous border. The lesions then ulcerated centrally, developing a central necrotic exudate characteristic of a perforating collagenosis. The resulting well-defined, oval-shaped lesions measured 2–3 cm in size and coalesced into large complex plaques, which were widely distributed across both flanks, the upper arms and dorsum of the hands bilaterally. Blood tests demonstrated poorly controlled diabetes, with a haemoglobin A1c of 71 mmol mol−1. His renal function was preserved. Given the association of acquired perforating collagenosis with solid organ and haematological malignancy, especially in the context of the patient’s history of renal cell carcinoma, computed tomography of the chest–abdomen–pelvis was arranged, which revealed only a benign lung nodule. The endocrinology team started insulin for the management of his diabetes, with a resulting improvement in his glycaemic control. The management of his pruritis with intensive emollients and potent topical corticosteroids, alongside optimization of his glycaemic control and treatment of infection, resulted in a full resolution of the lesions with only evidence of scarring at follow-up after 4 months. Perforating collagenoses are a group of disorders characterized by the elimination of collagen or elastin through the epidermis, and include elastosis perforans serpiginosa, Kyrle disease, perforating folliculitis, and reactive perforating collagenosis. They may be primary or secondary. Acquired reactive perforating collagenosis is recognized as an unusual form of transepithelial elimination of collagen fibres, which are extruded through the epidermis in patients with a genetic predisposition or underlying diseases, such as diabetes mellitus or renal diseases. The giant variant of the condition, in which lesions measure more than 1 cm, is rarely reported. Interestingly, cases in the literature commonly affect older patients. The aetiology is incompletely understood, but epidermal trauma secondary to scratching aiding the elimination of altered collagen may be implicated, and koebnerization is widely recognized. Epidermal thinning as a natural part of ageing may predispose older patients to this trauma, especially when combined with age-related pruritis due to compromise of the barrier function of the stratum corneum. Older patients may also be at increased risk of renal dysfunction or poor glycaemic control due to age-related insulin sensitivity, decreased endocrine pancreatic function and lifestyle factors.