**7.1 Medical history**

A detailed and solid medical history is one of the pillars of the diagnosis. It should include information about the environment in which the mother lives or lived, maternal diseases

Preventing dysmorphisms involves three main points: *genetic counseling, screening* and *monitoring during pregnancy*. The former two apply when the defect is hereditary or is

The basic recommendation in the case of genetic diseases in animals is that affected individuals should not breed and that normal couples with affected descendents should not breed again. However, owners of normal animals that have had affected descendents are not usually willing to follow this advice. With this in mind, when there is a correct diagnosis and the genetic nature of the defect is known, other decisions are possible, but the risk of recurrence should be taken into consideration. To avoid autosomal recessive phenotypes, an important strategy is never to mate individuals who are known to be heterozygotes one with another, such as those who have already had an affected descendent. For recessive Xlinked phenotypes, daughters of affected individuals are all carriers (heterozygotes) and should not be mated, even when the males are normal. When there is a family history of a recessive defect and the zygosity of an individual is unknown, consanguineous unions

When breeding small or large animals, identifying heterozygotes (recessive phenotypes and dominant phenotypes with reduced penetrance) can be an economically advantageous procedure and allows people to make appropriate preventive decisions concerning the mating of such individuals. For several recessive heredopathies commercial DNA tests are now available, significantly reducing costs. For instance, there is a test for arthrogryposis multiplex in cattle; for pulmonary hypoplasia with anasarca (PHA) in Dexter cattle; for polycystic kidney disease in cats, for Sly disease (mucopolysaccharidosis VII) in dogs; for hereditary microphthalmia in sheep. In abnormalities in which there is incomplete dominance between the mutant and normal allele, the heterozygotes can be identified visually because they have an abnormal phenotype, although it is less serious than that of homozygotes for the mutant allele. For example, there is a type of chondrodysplasia in cattle, common in the Dexter breed, in which the heterozygotes have shorter than normal limbs. If two chondrodysplasic individuals breed, there is a 50% risk of recurrence of the parents' phenotype (heterozygotes) and a 25% risk of a very serious and lethal chondrodysplasia, popularly known as a "bulldog calf", when the affected animals have

very short limbs and spine, and their heads somewhat resemble that of a bulldog.

Several aspects deserve attention during pregnancy: 1) Care should be taken not to expose the pregnant animal to teratogens in the environment (mercury, herbicides, toxic plants, organochlorides, etc.); 2) The animals should not be given medicine with teratogenic potential; 3) They should not be submitted to radiographic examinations. If this cannot be avoided, the abdomen of the pregnant animal should be protected with a lead apron or the

influenced by genetic factors. The latter is useful in any situation.

**8. Prevention of dysmorphisms** 

**8.1 Genetic counseling** 

should be avoided.

**8.3 Monitoring during pregnancy** 

**8.2 Screening** 

(metabolic disorders, infectious diseases, etc.), the mother's food, any medication given to the mother during pregnancy, and particularities of pregnancy and labor. Whenever possible, the veterinarian should seek not only similar cases but also different defects between sibs of the affected animal and other relatives. A pedigree should be drawn that is as complete as possible to facilitate the genetic analysis and enable the identification of an inheritance pattern when there is one.
