A description is made of the pathological findings of two fetuses affected by lethal congenital osteogenesis imperfecta. A review of the latest bibliography is made on the clinico-pathological, biochemical and genetic aspects of the four types of osteogenesis imperfecta (01) described in the classification of SILLENCE et al. The most constant skeletal alterations in lethal congenital 01 (type 11 of SILLENCE) are considered to be: a) Difficulty in the macroscopic identification of membranous bone of the cranial vault; b) Thin cortical regions consiting of reticular bony tissue with multiple chondrogenic fracture callus; c) Metaphyseal fractures with structural collapse; d) Absence of the RANVIER ossiflcation groove; e) Hyperosteocytosis with a decrease in the amount of bony tissue; f) lncrease in the size of the epiphyseal and growth cartilage vasculÍlr channels
