[Keratosis lichenoides chronica in two siblings with marked response to UVB phototherapy].

BACKGROUND: Keratosis lichenoides chronica (KLC) is a rare chronic keratinisation disorder. Out of almost 60 published cases of KLC, only two report its occurrence in siblings. We report a new case in which a brother and sister present KLC that improved markedly with UVB phototherapy. PATIENTS AND METHODS: A 10-year-old girl presented with hyperkeratotic papules symmetrically arranged in a reticular pattern on the face and the extremities. Onset occurred at the age of six months. For a number of years, minimum sunlight was allowed owing to a diagnosis of lupus. However, KLC was our first diagnostic assumption, confirmed by an elbow lesion biopsy sample. The patient's brother, one and a half years old, had been presenting similar lesions since the age of two months. Sibship was demonstrated by DNA analysis using short tandem repeat markers. No consanguinity was found. After one month of narrow-band UVB phototherapy, most of the papules had flattened. DISCUSSION: KLC is uncommon in childhood and familial occurrence is very rare. Clinically, thick keratotic papules arranged in parallel lines or small networks cover the dorsal aspects of the limbs symmetrically. The face may be affected by a seborrhoea-like dermatitis. Histology typically shows alternating acanthosis and atrophy, with focal parakeratosis. An extensive lichenoid lymphohistiocytic and plasmocytic infiltrate is demonstrated in the dermis. The course is chronic. Spontaneous resolution may occur. Sunlight has been shown to be effective in the few paediatric cases reported. Narrow-band UVB phototherapy appears to be an effective therapeutic option.