External and internal genitalia can be malformed by genetic and environmental factors without involvement of sex chromosomes or fetal gonads. Thus, genital dysmorphology may be part of many syndromes of various etiology, such as monogenetic disorders, autosomal chromosomal abnormalities and non-random malformation syndromes of unknown etiology. Genital dysmorphology may also occur as a result of teratogenic effects following maternal ingestion of synthetic progestins. The genital manifestations in all these syndromes occur more commonly in males than in females. Penetrance and expression of these abnormalities tend to show great variability.