Severe neuroimaging anomalies are usually associated with random X inactivation in leucocytes circulating DNA in X-linked dominant Incontinentia Pigmenti

Incontinentia Pigmenti (IP) is a skin disorder with neurological impairment in 30% of cases. The most common disease causing mutation is a deletion of exons 4-10 of the IKBKG gene, located on chromosome Xq28, with skewed X-chromosome inactivation in females, but few cases of random X-inactivation have been reported. We have correlated brain anomalies with X-chromosome inactivation status determined on leucocytes circulating DNA. We reviewed MRI of 18 girls with genetically proven IP. We found three patterns of MRI, normal MRI (n = 5), mild white matter abnormalities with cortical and corpus callosum atrophy (n = 6), and severe cortical abnormalities suggesting a vascular disease (n = 7). Most patients with severe abnormalities had random X-inactivation (6/7,86%), while 80% (4/5) of patients with normal MRI and 100% (6/6) of patients with mild white matter abnormalities had skewed inactivation. These results suggest that skewed chromosome X-inactivation may protect brain from damage, while in case of random inactivation, expression of the mutated IKBKG gene may lead to severe brain lesions.