A progressive neurological condition characterised by megalencephaly, spasticity, ataxia and seizures in two siblings of consanguineous parents is described. The electroencephalogram showed posterior discharges and an unusual photoparoxysmal response whereas brainstem auditory evoked potential findings were consistent with a white matter disorder. Computerized tomography scans revealed diffuse hypodensity of the white matter and a brain biopsy on one sibling showed features of dysmyelination without evidence of demyelination, Rosenthal fibres or the spongy changes characteristic of Canavan's disease. There was no detectable biochemical abnormality. This combination of clinical, neurophysiological and neuropathological abnormalities has not previously been described.

Two siblings with marked subcutaneous tissue atrophy, delayed dentition and a degenerative neurological condition characterised by nystagmus, ataxia and spasticity are described. Myelin was almost totally absent on the magnetic resonance image brain scan performed on one sibling. There was no history of photosensitivity and ultraviolet irradiation of cultured fibroblasts did not inhibit RNA synthesis. We believe that these children have a previously undescribed syndrome, which, although clinically similar to Cockayne syndrome, is readily distinguished from it.

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The association of microcephaly and mental retardation with a non-pigmentary retinopathy is described in three siblings of consanguineous parents. The electroretinogram showed the distinctive appearance of markedly attenuated "b" wave but normal "a" wave suggestive of a retinal dystrophy primarily affecting post-receptoral elements in the inner retina. This appears to be an autosomal recessive condition which has not been previously reported.