Polymorphic dermatosis

Paediatric dermatology

Dr. Emmanuelle Bourrat

Saint-Louis Hospital

The clinical case
Now it's your turn!
Co-prescription and advice

Clinical case presentation

This 10-year-old child had been treated for familial scabies a year earlier and considered cured despite the persistence of asymptomatic bilateral axillary lesions.

Over the past few months, he had noticed the appearance of painless, non-pruritic papules multiplying in the suprapubic region.

Dermatological examination showed markedly different lesions in the two areas: in the armpits, normal skin-colored papules measuring 3 to 5 mm (1), and on the abdomen, millimetric flat yellow-brown papules (2). There were no signs of active scabies and the rest of the examination was unremarkable.

Your turn

What is your diagnosis?

Select 1 answer(s) from the following choices:

Pseudoxanthoma elasticum (PXE)

Histiocytosis of the xanthogranuloma group (juvenile xanthogranuloma, JXG)

Co-occurrence of PXE and JXG

Eruptive syringomas

Wrong answer!

Good answer!

Selected diagnosis

Histologically, in the superficial and mid-dermis, an epithelial proliferation was observed, consisting of small cord-like structures and glandular cavities within densified collagen.
These cavities were bordered by a double layer of regular, non-atypical cells.

These are therefore eruptive syringomas of the trunk, with slow progression, currently of no aesthetic concern, and requiring no investigation. Even in familial, and therefore probably genetic forms, there is no extracutaneous or syndromic involvement.

Explanation of wrong answers

Pseudoxanthoma elasticum (PXE) is a genodermatosis that begins in childhood, although clinical expression in dermatology and ophthalmology is rarely evident until adulthood. Skin involvement is manifested by asymptomatic ivory or yellow papules located in the major folds (neck and armpits in particular). Histologic confirmation is essential.
Histiocytosis of the xanthogranuloma group is not uncommon in children of all ages, in the form of juvenile xanthogranulomas (JXG), which may vary in number and distribution but are most often characterized by a papular appearance and yellow discoloration.
Co-occurrence of PXE and JXG: The clinical diagnostic hypotheses were therefore axillary pseudoxanthoma elasticum and suprapubic juvenile xanthogranulomas. Two skin biopsies were performed, as the clinical appearance was far from typical for either diagnosis and the coexistence of two different conditions seemed unlikely. The histological appearance was identical at both sites and allowed elimination of both hypotheses.

Treatment

We explain to parents that these are benign, non-syndromic adnexal tumors whose purely cosmetic treatment (laser or electrocautery) is often long and disappointing (risk of scarring and recurrence).

Message from the expert

Eruptive syringomas are small, monomorphic, non-itchy papules that are often highly hyperpigmented on genetically darker skin and less visible (and perhaps underdiagnosed?) on fairer skin.
In all cases, histologic confirmation is required.