CPC07 Lupus comedonicus: a not so common entity

Abstract

Lupus comedonicus (LC) is an exceedingly rare variant of chronic cutaneous lupus erythematosus (CCLE), with only 13 reported cases in the literature to date. While its aetiology remains unknown, hallmarks include the presence of comedones on erythematous plaques, particularly in seborrhoeic areas. We report a case of LC involving the scalp, concha bowl and upper back. A 53-year-old female smoker with a 20-pack-year history and previous unprovoked pulmonary embolism presented to dermatology with a 2-year history of alopecia and rash affecting her face and upper back. She was initially reviewed by oral medicine for ulcers, where erythematous buccal mucosal plaques with white striations were seen. The initial biopsy showed a patchy lichenoid inflammatory infiltrate, raising suspicions for lichen planus; however, repeat biopsy highlighted perivascular inflammation and keratin plugging suggestive of lupus. Full skin examination revealed patchy scarring alopecia with perifollicular scale and erythema. Erythematous infiltrated plaques were seen on the face with similar more indurated lesions on the upper back associated with open comedones. The eponymous Shuster sign was observed in the left conchal bowl, with associated follicular occlusion. Laboratory studies all returned within normal limits, including antinuclear antibody titres and complement levels. Differential diagnosis included lupus erythematosus tumidus, discoid lupus erythematosus and LC. Lesional biopsies taken from her back confirmed LC, highlighting lichenoid inflammation involving follicles and interfollicular skin, with superficial and deep perivascular infiltrate. We commenced oral hydroxychloroquine at 200 mg once daily for management, with topical mometasone furoate 0.1% to be used while awaiting its full effect. Smoking cessation has also been advised given the potentially antagonistic effect of smoking with lupus and hydroxychloroquine. Hypotheses of the pathogenesis of LC include the effect of sun exposure. Ultraviolet radiation is known to not only enhance the activity of CCLE but may also contribute to the formation of comedones. Actinic damage alters collagen of normal skin, promoting sebum retention and follicular plugging. Given its infrequency, LC could be mistaken for benign conditions, including acne vulgaris, naevus comedonicus and Favre–Racouchot disease. It is plausible that the small case numbers are due to current underdiagnoses. It is important for dermatologists to be aware of and accurately diagnose LC. Apart from its potentially destructive, scarring complications, especially in untreated and misdiagnosed cases, it is associated with systemic lupus in 30% of cases. Delay in diagnosis and therapeutic management can be associated with significant potential morbidity and even mortality.