[Annular lichenoid dermatitis of youth: A case report and literature review].

BACKGROUND: Annular lichenoid dermatitis of youth (ALDY) is a rare form of dermatitis mainly affecting children and young people. All cases reported show a consistent clinical and histological picture. This is the first case described in the French literature.

PATIENTS AND METHODS: A 5-year-old girl presented an annular isolated patch of the lower abdomen with an erythematosquamous border and central hypopigmentation for one year. Topical corticosteroids and pimecrolimus proved effective but relapse occurred after treatment withdrawal.

DISCUSSION: Over sixty cases of ALDY are described in the English-language medical literature. The main differential diagnosis is childhood mycosis fungoides, particularly the hypopigmented variant. Biopsy is necessary for diagnosis since it can reveal typical histological features. Histopathology in all cases shows lichenoid reaction with CD4+ and CD8+ polyclonal lymphocytes. It is limited to the tips of rete ridges and associated with apoptosis of keratinocytes resulting in quadrangular-shaped rete ridges. Our case does not demonstrate either epidermotropism or atypical lymphocytes.

CONCLUSION: Annular lichenoid dermatitis of youth (ALDY) is a poorly known distinctive entity within the lichenoid dermatitis family. Clinical-histological correlation is essential to diagnosis. The etiology is still unknown and the course is mostly chronic.