Background: Hypochromic streaks can be the only cutaneous sign of incontinentia pigmenti (IP) in adulthood (stage IV). Discovery of such lesions in an adult female with no family history of IP is essential for appropriate genetic counselling.
Objective: To describe and to validate the histological features of residual skin lesions in adult IP.
Methods: The analysis and comparison of skin biopsies of 26 women affected with molecularly confirmed IP.
Results: Most biopsies showed slight atrophy and some scattered apoptotic cells in the epidermis, epidermal hypopigmentation and reduced melanocyte number. The dermis appeared thickened and homogeneous and revealed a complete absence of hair follicles (23/26) and sweat glands (22/26). There was no melanin incontinence or inflammatory cells, and the elastic network was normal.
Conclusion: These features lead unequivocally to the diagnosis of a stage IV IP skin lesion. Consequently, histology is a major confirmatory criterion for diagnoses of these mild clinical forms of IP. It is therefore a useful tool in genetic counselling and prenatal diagnosis. Moreover, the observations described here may contribute to understanding the physiopathology of the late stages of IP.