[Fatal nanism: 3 different entities].

Three cases of congenital dwarfism are presented. All of them are lethal and represent the three better known nonviable nosologic entities: Achondrogenesis I, Achondrogesis II and Thanatophoric dwarfism. According to clinical features and radiologic data it is possible to approach the diagnosis accurately. We comment genetic, clinic, radiologic and histologic aspects of these processes. It is important to establish a differential diagnosis as these entities have different genetic basis, what influences genetic counsel.