A New Ultrastructural Finding in Oral Submucous Fibrosis

Summary.— Oral submucous fibrosis and progressive systemic sclerosis (scleroderma) show clinical and histological similarities, but there are also differences in distribution and prognosis. So far there has been no evidence of any connection between these diseases. Transmission electron microscopy of connective tissue from a patient with oral submucous fibrosis shows, however, that the normal pattern of uniform size fibrils gathered together in bundies is replaced by an excess of fine (im‐mature) fibrils and of interfibrillar matrix. The average flbril diameter was 36.2 nm compared with the normal of 49.7 nm from the same area, while the concentration was 210 to 240 fibrils/μm2 compared with 170 to 180 in the normal. Though the ultimate causes of progressive systemic sclerosis and of oral submucous fibrosis probably differ, it seems likely that they share a defect of collagen maturation which gives rise to a clinically similar lesion.