DP04 A case of elastosis perforans serpiginosa in a patient with trisomy 21

Abstract A 16-year-old girl with a background medical history of trisomy 21, psoriatic arthritis and scalp psoriasis was referred from rheumatology for assessment of a rash. Regular medications were notable for tofacitinib to treat her psoriatic arthritis, moderately potent topical steroid preparations, and coal tar shampoo to treat her scalp psoriasis. The rheumatologists queried whether this rash was a psoriasiform eruption in the setting of tofacitinib and whether a change of immunosuppression was warranted. On examination, she had an annular rash with studded keratotic papules around the periphery. This rash was asymptomatic. The clinical differential diagnosis included granuloma annulare and elastosis perforans serpiginosa (EPS). Initial histology revealed mild hyperkeratosis and mild epidermal acanthosis. It was nonspecific and she was treated with topical corticosteroids with no benefit. Repeat histology from one of the keratotic papules revealed prominent degenerative elastic fibres with aggregates of neutrophils in the follicles consistent with EPS. EPS is a rare skin disorder first described in 1953 and is characterized by transepithelial elimination of elastin fibres and focal dermal elastosis. It is one of four classic primary perforating dermatoses, including reactive perforating collagenosis, perforating folliculitis and Kyrle disease. Noted associations with EPS include connective tissue diseases such as cutis laxa, pseudoxanthoma elasticum, Ehlers–Danlos syndrome (EDS), Marfan syndrome and systemic sclerosis; trisomy 21; Rothmund–Thompson syndrome; and medications such as D-penicillamine. The exact pathomechanism of EPS is unknown, but it has been suggested that a 67-kDs elastin receptor is present in keratinocytes associated with the elimination of elastin in EPS, which may explain the role of the elastin–keratinocyte interaction in the transepidermal elimination of elastin. Regarding EPS in the setting of trisomy 21, it is hypothesized that there is known premature skin ageing and joint hyperlaxity in trisomy 21, indicating a subtle disorder of connective tissue. Treatment of EPS often proves unsatisfactory. Reported treatments include topical corticosteroids, topical retinoids, cryotherapy, topical imiquimod, narrowband ultraviolet B radiation, oral isotretinoin and ablative carbon dioxide laser, with variable results. This case highlights that EPS should be considered in patients with trisomy 21 given the association. It also highlights that when undertaking a biopsy in suspected EPS it is important to take samples from the keratotic papules to ensure diagnostic accuracy.