Hypomelanosis of Ito (HI) is a rare neurocutaneous disorder characterized by hypopigmented macules along the Blaschko line and multiple abnormalities, including seizures, developmental retardation, ophthalmologic defects, and chromosome mosaicism. [ncbi.nlm.nih.gov]

He was observed to have short extremities, and radiographs were consistent with achondroplasia. The serum alkaline phosphatase level was 2 IU/dL. [ncbi.nlm.nih.gov]

On the tenth day of treatment, he developed frequent partial seizures, characterized by being motionless during the seizure with eye deviation to the right. [ncbi.nlm.nih.gov]

[…] clinical spasms may manifest in absence of hypsarrhythmia [infantile spasms without hypsarrhythmia (ISW)]. [ncbi.nlm.nih.gov]

Interictal The background EEG is often highly disorganized with high voltage irregular slow waves intermixed with multifocal spikes and polyspikes, this is termed 'hypsarrhythmia'. [epilepsydiagnosis.org]

The interictal EEG pattern is described as hypsarrhythmic as it is characterised by asynchronous and high-amplitude slow waves and multifocal spikes. Both fast and slow variants, depending on the aetiology, have been reported. [orpha.net]

Hypsarrhythmia is a characteristic interictal pattern of chaotic, high to extremely high-voltage polymorphic delta and theta rhythms with superimposed multifocal spikes and wave discharges. [patient.info]

[…] and slow-wave activity (Gibbs and Gibbs 1952). [medlink.com]

Interictal EEG recording during n-REM sleep and wakefulness displayed diffuse and asynchronous high voltage spikes and slow waves suggesting the hypsarrhythmic pattern (Figure 1 A). Figure 1 A. [bmcneurol.biomedcentral.com]

(B) Representative EEG with spike and slow waves. (C) Representative EEG with a normal background. [nrronline.org]

It associates IS with a typical EEG pattern called hypsarrhythmia consisting of random, high-voltage, nonsynchronous spikes and slow waves and developmental delay. [nature.com]

Other patterns, such as multifocal independent spike discharges (MISD), are present in the remainder. Although infantile spasms may be associated with other EEG abnormalities, hypsarrhythmia virtually never occurs in other epilepsy syndromes. [ncbi.nlm.nih.gov]