Involvement of the white matter in hypomelanosis of Ito (incontinentia pigmenti achromiens).
We report our clinical and neuroradiologic findings in 13 patients affected by hypomelanosis of Ito. Seven patients were boys and six were girls; their ages ranged from 11 months to 16 years. Neurologic signs were present in all but two cases, and they consisted of language disabilities, seizures, hypotonia, mental retardation, and autistic behavior. MRI was performed in all patients. We observed anomalies of the white matter in seven of the 13 patients; all but one of these seven had neurologic signs that included seizures, hypotonia, language disabilities, and mental retardation. The abnormal signals in the white matter were mostly located in the parietal periventricular and subcortical regions of both hemispheres. Moreover, we found asymmetry of the cerebral hemispheres in one of our 13 patients and atrophy of the cerebellar vermis in another patient, with no involvement of the white matter in either. In the remaining four of the 13 patients results of MRI appeared normal. There was a relationship between the anomalies in the central nervous system at MRI, as a whole, and the neurologic manifestations, even though two patients with apparently normal images on MRI had partial and generalized tonic clonic seizures, respectively. A correlation was also found between white matter anomalies and neurologic signs; extended and deep changes in white matter images were associated with more severe neurologic abnormalities and delayed language milestones appeared to be a constant finding in this group of patients. These anomalies of the white matter, which did not progress over time, resembled those seen in other neurocutaneous syndromes. The hypothesis is presented that underlying disarray of cortical lamination or neuronal loss with subsequent wallerian degeneration and altered or delayed myelination could be the cause of the abnormal findings on MRI.