AN ULTRASTRUCTURAL STUDY OF THE RETINA IN HUMAN LATE INFANTILE NEUROAXONAL DYSTROPHY

Abstract

A case involving a girl who died at 11 years of age and who had developed normally until the age of 18 months, at which time further psychomotor maturation stopped and then regressed, is reported. The patient appeared hypotonic and showed loss of deep tendon reflexes, as well as bulbar signs and increasing immobility. Visual impairment resulted in blindness at the age of 7 years. Her disease was diagnosed as late infantile neuroaxonal dystrophy (LINAD) after examination of sural nerve biopsy samples and after autopsy. Under electron microscopy, retinal axons were filled with tubulocisternal profiles and occasional large lamellar clefts close to or distant from synaptic complexes. These lesions, typical of LINAD, were largely found in interior layers of the retina rather than in outer ones. As photoreceptors were preserved and their synaptic contacts within the outer nuclear layer appeared somewhat intact, blindness in LINAD is of the neuronal type, possibly all along the pathway from the bipolar retinal layer to the striate cortex. The findings also indicate that only particular types of axons or synaptic complexes may be involved in LINAD, and that the formation of lesions characteristic of LINAD is not ubiquitous within the retina. The cause for this selective involvement of retinal structures in LINAD remains to be resolved.