Hypomelanosis of Ito (HI) is characterised by hypochromic unilateral skin lesions, hemi‐hypertrophy, mental retardation (MR) and seizures.1 We describe a young woman with HI with interesting and hitherto unreported magnetic resonance imaging (MRI) changes.
A 22 year old woman presented with a history of uncontrolled generalised tonic clonic seizures and myoclonic jerks since the age of 2 years. She had hypopigmented macular lesions in streaks and whorls on her right side in a dermatomal distribution (fig 11 A–D). There was hemihypertrophy of the right upper extremity, and it measured 15 mm longer than the left (fig 1C1C).
She had moderate to severe MR with an intelligence quotient of 33.3 on the Binet‐Kamat test of intelligence, and a and social quotient of 32.3 on the Vineland Social Maturity scale. MRI brain revealed right hemimegalencephaly, temporoparieto‐occipital pachygyria, and absence of the anterior limb of the sylvian fissure (fig2A–D). Scalp EEG revealed slowing of background activity and bihemispheric epileptiform discharges.
The term "hypomelanosis" was introduced by Ito and is perhaps the fourth most common neurocutaneous syndrome.2,3 Characteristically these patients have hypochromic unilateral or bilateral lesions in whorls, patches, and streaks, with a midline cutoff. Neurological involvement is noted in 76% of patients, with seizures and MR being common. Other features include ataxia, neuropathy, distal spinal muscular atrophy, torticollis, deafness, and spina bifida occulta. Hemimegalencephaly on either side of skin lesions, hemihypertrophy often ipsilateral to hypomelanotic lesions,5 arm and leg length discrepancy, and scoliosis are also noted. Neuroimaging may reveal hypoplastic corpus callosum, heterotopias, periventricular white matter changes, vascular malformations, medulloblastoma, and choroid plexus papilloma.4,5
Our patient had the classical phenotype of HI and a few novel findings such as ipsilateral pachygyria and absence of the anterior limb of the sylvian fissure.