1. Clinical and laboratory studies are reported on a 13½ year old boy, the offspring of a consanguinous marriage, who, after having been afflicted with a celiac syndrome in early childhood, developed a progressive ataxic neuropathy associated with a peculiar malformation of most of his circulating erythrocytes. Similar observations were previously described in the literature in two siblings also of consanguinous parents. The latter patients, however, had in addition, retinitis pigmentosa.
2. The erythrocytic anomaly consisted of an unusual type of "crenation"; the deformed red cells showed several, irregularly spaced, large and coarse projections on their surface which varied in width and length. Many of the cells resembled spherocytes with pseudopods. The term acanthrocyte (thorny red cell) is proposed for this particular type of misshapen erythrocyte.
3. The acanthrocytes exhibited a slightly decreased osmotic, a markedly increased lysolecithin and mechanical fragility, hut a normal heat and acid fragility.
4. The hemolytic index was within normal range, a finding which seems to preclude the existence of an exaggerated hemolytic process in vivo.
5. It is suggested that acanthrocytosis is genetically conditioned, and due to a mutant recessive allele for a gene which controls the normal architecture of the red cell.
6. Further observations are required to establish whether the association of acanthrocytosis, celiac disease in early childhood, and ataxic neuropathy with or without retinitis pigmentosa constitutes a new hereditary syndrome.