[Retroauricular dermatitis of the "milia en plaque" type].

We report 3 cases of very rare dermatoses with retroauricular location, having lesions of "milia en plaque" type. These dermatoses are the retroauricular follicular lichen planus tumidus, the retroauricular "milia en plaque" and an exceptional case of sebocystomatosis (steatocystoma multiplex) with exclusively retroauricular location, which is unique in the literature. In this group of retroauricular dermatoses can also be included the small retention cysts and comedones of the retroauricular area, attributed to paraffin products in shaving soap inadequately rinsed from this region. On the occasion of these cases we make a review of the literature and a detailed study of the retroauricular follicular lichen planus tumidus and retroauricular milia en plaque and we discuss the differential diagnosis emphasizing the clinical and histologic features, which permit to make the accurate diagnosis.