Mixed gonadal dysgenesis is a genetic condition that causes abnormal development of the sex organs, often causing the sex organs to appear ambiguous (having features of both male and female). The most common sign of the condition is asymmetric gonads (some male and some female internal sex organs), with an individual having an undescended testis on one side of the body and a malformed or underdeveloped “streak” gonad on the other side (beginning of an ovary). The external genitalia also is ambiguous. Individuals with this condition are infertile, and the ambiguous sex organ appearance may make it difficult to classify them as male or female at birth. The abnormal sex organ development is most commonly caused by abnormal sets of sex chromosomes (the genetic material that determine whether a person is a male or female). Normal females have XX sex chromosomes and males XY sex chromosomes. People with this condition usually have a mix, with some cells having XY (the normal male set) and other cells having X0 (an abnormal female set). The expression of both male and female sex chromosomes causes the sex organs to develop abnormally. A genetic test called a karyotype that counts chromosomes can confirm a diagnosis of the condition. Although individuals with this condition are neither biologically male nor biologically female, sex assignment surgery can help individuals, if they so choose, maintain a normal female or male appearance. In addition to differences in sex organs, people with this condition are usually shorter than average and are at higher risk for gonadal cancer. Because of this risk, health care providers often recommend removal of gonads or frequent ultrasounds for cancerous growth. Talking with your baby’s physician as well as genetic and other specialist will help you understand the condition and determine the best care plan. Finding support from other families affected with mixed gonadal dysgenesis mixed may also be very helpful.