Patient Consultation: My family’s ichthyosis probably started with my grandmother’s father, who was not sick. Grandma had two sons with the disease (including my dad), and three aunts without the disease. Dad had two daughters, my sister and I, and we are symptom-free. My sister gave birth to two sons, the eldest son is very serious, born with peeling skin, currently very serious, the youngest son is currently one year old, no symptoms for now. I gave birth to a daughter who is now seven years old and has small patches of ichthyosiform skin on her lower legs. Is this sex-linked ichthyosis and why is it mild in my daughter, including my cousin’s child? My response: From the family history, it is indeed possible that this family is suffering from sexual interlocking ichthyosis. Her father had two daughters who did not have the disease, but her sister’s oldest son had severe ichthyosis, somewhat like what we often call intergenerational inheritance. However, the so-called intergenerational inheritance is not really intergenerational, but the male passes the disease causing gene to the female, and the female is the carrier, i.e. she has the disease causing gene and does not show the disease, but the female may have the disease if she has another boy. In this family, the disease is likely to be sex-linked ichthyosis. Both she and her sister inherited the X chromosome from their father, so both of them must be carriers, and therefore the boy born to her sister has a 50% chance of having the disease. Sex-linked ichthyosis, which is not a disease in women, but the consultant’s daughter has mild small patches of ichthyosis-like skin, it is possible that it is just a manifestation of common ichthyosis and not sex-linked ichthyosis. This is because sex-linked ichthyosis would not be a limited manifestation, but rather a generalized, smudgy colored scaling all over the body. It is possible here that she or her husband carries both the causative gene for common ichthyosis, causing her daughter to have mild symptoms, but it is certainly not sexual interlocking ichthyosis, but just common ichthyosis and sexual interlocking ichthyosis that happen to cross over in this family. However, if she has another child, it will depend on whether it is a male or female, if it is a female it will only be a carrier and will not show sex-linked ichthyosis, if it is a male there is a 50% chance that it will show more severe sex-linked ichthyosis, like the older child of the sister. Generally speaking, genetic testing is recommended that it is best to get blood samples from all relatives to get a higher accuracy. For this family, what is definitely needed are blood samples from her grandparents (if still alive), her father’s siblings, and her and her sister, as well as her sister’s oldest son and her daughter can be collected. The more complete the family’s blood samples, the more reliable the results of the genetic test will be. After collecting the blood samples, we first detect the defective loci in the patient’s blood samples, for example, we can detect the mutation of STS gene related to sex-linked ichthyosis from the sister’s oldest son or her father’s blood samples; after the testing is completed, we then extend the testing to detect the mutation loci of other related members of the family to make genotyping judgment, for example, she and her sister, and then we know that she and her sister are The genotyping will also suggest whether her daughter may also carry the disease-causing gene, because her daughter also has a 50% probability of carrying the disease-causing gene. On this basis, we will provide her with prenatal diagnosis, and if her next pregnancy is indeed a boy, DNA will be extracted from the chorionic villus or amniotic fluid during pregnancy, and the DNA will be analyzed to determine whether the child will inherit the same sex-linked ichthyosis as his father by analyzing whether the DNA carries the mutation loci of the family STS pathogenic gene. If the child is determined to be female in the early stages of pregnancy, then at least for the time being, we can rest assured that the disease will not be inherited, and at most, the child will be a carrier of the disease-causing gene, and if we get such a result, we can have a child with complete peace of mind; if the child is male, and the genetic test tells us that the fetus is normal for the STS gene, and no mutation loci of the family disease-causing gene are inherited, then we can have a child with peace of mind that the disease will not be transmitted.