Diagnosis of neuronal ceroid lipofuscinosis by ultrastructural examination of peripheral blood lymphocytes.

A 7-year-old child with a history of seizures, psychomotor regression, and progressive visual loss was found to have juvenile type neuronal ceroid lipofuscinosis on the basis of characteristic ophthalmoscopic and electroretinographic findings. Although transmission electron micrographs of two separate skin biopsy specimens were normal, peripheral blood lymphocytes were vacuolated and demonstrated, by ultrastructural examination, characteristic "fingerprint profiles" confirming the diagnosis. Peripheral blood lymphocytes from the patient's mother, who had an acquired seizure disorder, demonstrated vacuolated lymphocytes with membranous formations and osmophilic granular bodies, as revealed by electron microscopy. Examination of peripheral blood lymphocytes can be a sensitive diagnostic test in suspected neuronal ceroid lipofuscinosis and may be useful in identifying carriers or family members in the early clinical stages of the disease.