1. ¹Service de dermatologie, Hôpital Tenon, Paris, France
2. ²UPRES EA2396, Pierre et Marie Curie (Paris VI) School of Medicine, Paris, France
3. ³Service d'anatomie pathologique, Hôpital Necker, Paris, France
4. ⁴Service de dermatologie, Hôpital Necker-Enfants Malades, Paris, France

Correspondence: Dr Christine Bodemer, Service de Dermatologie, Hôpital Necker Enfants Malades, 149 rue de Sèvres, 75015 Paris, France. E-mail: christine.bodemer@nck.aphp.fr

⁵These two authors contributed equally to this work and share senior authorship

Received 21 March 2005; Revised 6 June 2005; Accepted 14 July 2005; Published online 29 December 2005.

Abstract

During pregnancy, maternal cells may enter the fetal circulation and persist until adulthood. The fate of these cells remains unknown. As unexplained T-cell-mediated conditions such as pityriasis lichenoides (PL) may occur in children, we aimed at identifying maternal cells in lesional skin of PL and controls. Archived skin biopsy specimens from young males with PL, atopic dermatitis, or normal skin were scanned for the presence of female (presumably maternal) cells using fluorescence in situ hybridization (FISH) with X and Y chromosome-specific probes. Phenotyping of maternal cells relied on FISH combined with anti-CD45, anti-CD1a, or anti-cytokeratin labelling, identifying leukocytes, Langerhans cells, and keratinocytes, respectively. Maternal cells were found in PL (11/12) and controls (4/7), but their average frequency was higher in PL: 99 per million cells as compared to 5 per million cells in controls (P=0.005). In the epidermis, the maternal microchimeric cells were labelled by anti-cytokeratin in all cases. We identified maternally derived keratinocytes in the skin of male children with inflammatory skin disorders. These cells may either help repair the damaged skin or home initially in the skin and trigger a host (child) versus graft (mother) disease.