Feline Large Granular Lymphoma

there is disproportionate lengthening of the fibulae. The bone changes present in homozygous achondroplasia even more closely resemble thanatophoric dwarfism, but this can be easily ruled out by the case history since this entity only results from the mating of two heterozygous achondroplastic parents. Achondroplasia usually is compatible with life and is not considered a lethal dwarfism. Achondroplasia and thanatophoric dwarfism are readily distinguishable by histopathology. Unfortunately, due to the numerous diagnoses of thanatophoric dwarfism as achondroplasia prior to 1967, there is considerable confusion in the literature about the histopathologic appearance of achondroplasia. There is now general agreement that achondroplasia has a relatively normal appearing growth plate with only minor qualitative changes in contrast to the marked distortion of the growth plate in thanatophoric dwarfi~m.~,l~ The defect in achondroplasia is a quantitative defect in endochondral ossification, whereas in thanatophoric dwarfism there is a severe qualitative defect with subsequent quantitative reduction in endochondral ossification. Although thanatophoric dwarfism has not been previously reported as such in animals, we agree with Rimoin9 that hereditary achondroplasia in rabbits may be an example of thanatophoric dwarfism in animals rather than achondroplasia. It is a congenital lethal dwarfism with radiographic and histologic features similar to thanatophoric dwarfism in man and to those reported here.8 t