A rare cause of hyperpigmentation in children

In the epidermis of normal thickness, there is neither keratinocyte necrosis nor vacuolation of basal keratinocytes. The underlying dermis contains abundant melanin pigment deposits, either free or taken up by melanophages. There is discrete perivascular lymphocytic and histiocytic inflammation.

This histological appearance is compatible with the clinical hypothesis of idiopathic eruptive macular pigmentation in children, which meets De Galdeano's anatomoclinical diagnostic criteria.

The identification of this benign but rare dermatosis, whose pathophysiology is poorly understood, has the main advantage of reassuring parents and avoiding unnecessary check-ups and follow-up; however, there is no known effective treatment. The spontaneous prognosis is assumed to be favorable, as this dermatosis is little or not described in adults. In the latter, erythema dyschromicum perstans and ashy dermatosis are mainly described, possibly as semiological variants but with a more chronic course.

• The macules of cutaneous mastocytosis can sometimes be highly pigmented in darker phototypes. Darier’s sign is used to make the diagnosis, which is confirmed by biopsy in cases of doubt.
   
• Multiple café-au-lait spots are suggestive of a genodermatosis, primarily neurofibromatosis type 1, especially if congenital or of very early onset. When the phenotype becomes complete (by around age 7 at the latest), these spots must be more than six in number and are always associated with another dermatological sign (lentigines, neurofibromas) or extracutaneous sign, or with a family history.
   
• The pigmented sequelae of fixed erythema pigmentosum are always preceded by an elementary inflammatory lesion (erythema, bulla) and medication.