Neuronal ceroid-lipofuscinosis: ultrastructural study of lymphocytic dense bodies.

We studied the ultrastructural alterations of the dense bodies of peripheral blood lymphocytes in one case of neuronal ceroid-lipofuscinosis. These cytoplasmic vesicles were characterized by vacuolar transformation and "fingerprint" content. When we tilted the specimens, the "fingerprint" arrangement was shown to be the same as the arrangement of the crystalloid inclusions found in the same cells. Both vacuoles and periodic cytoplasmic inclusions could be due to a disorder of secondary lysosomes--the lymphocytic dense bodies.