Author: Dr Ian Coulson, Consultant Dermatologist and Editor-in-Chief, 2022.
Edited by the DermNet content department
This seven-day-old girl has developed a rash distributed only on the left forearm in the last few days. There are some vesicles and pustules, and a biopsy of one of these has shown an epidermal vesicle full of eosinophils.
This is the early vesicular phase of incontinentia pigmenti, an inherited condition which affects the skin, eyes, teeth, and central nervous system.
It is inherited as a sex-linked dominant condition on the X chromosome. It is usually incompatible with life in utero in males, and therefore manifests only in females.
Early in life, the rash is vesicular with eosinophil-filled vesicles. Later, lesions become warty (verrucous phase), before becoming hyperpigmented. In all phases, the rash follows the lines of Blaschko.
