An autopsy case of cyclopia with 13 trisomy with special reference to histological abnormalities of the eyeball

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We present an autopsy case of cyclopia and alobar holoprosencephaly and Polydactyly with 13 trisomy. A 27 year‐old Japanese female at the 27th gestational week was diagnosed as hydramnios and the fetus showed hydrocephalus and intrauterine growth retardation. The fetus was suspected to be cyclopic and holoproscncephalic by ultrasonograph and MRI images. The mother delivered a stillborn male baby at the 30th week of gestation. At autopsy, the baby showed true cyclopia having one eyeball and two irides in a single ocular opening, and one proboscis. On histological analysis of the eye, there was marked dysplastic hyperplasia of the retina with rosettes, focal degeneration of the retina with calcification, and prominent proliferation of glial cells beneath the hyperplastic retina. Multiple glomerular structures in the cerebral cortex and aplasia of the corticospinal tract were observed. In the spinal cord, a few neurons with pyknosis were observed in the ventral horn. Although no mutation was detected in the Sonic hedgehog in the present case, we reviewed recent studies concerning the molecular mechanisms of cyclopia and holoprosencephaly.