There are many different inherited kidney diseases. Often patients and doctors do not know the cause of an inherited kidney disease in their family.
There are two things that are important to know about an inherited kidney disease:
How is the kidney disease inherited?
It is important to know which relatives have kidney disease, including brothers, sisters, and parents - but also grandparents, aunts, uncles, and cousins. It is important to go back as far as possible in the family tree to identify affected and unaffected individuals. From this information, an inheritance pattern can be determined.
Autosomal dominant inheritance pattern: Except for genes on the X or Y chromosome, we have two genes (alleles) for each protein that the body makes. For each protein in the body, children will inherit one allele from the father and one from the mother. In autosomal dominant disorders, symptoms and signs of the disease occur when there is only one abnormal (mutated) copy of a gene. Thus, an affected individual will have one normal and one abnormal copy. In autosomal dominant disorders, the child will get one of the two normal alleles from the unaffected parent and either the normal allele from the affected parent (resulting in two normal alleles and no disease) or the abnormal allele from the affected parent (resulting in one normal and one affected allele and the presence of disease). Thus, children of an affected individual have a 50:50 chance of inheriting the disease.
For autosomal dominant diseases, there are usually many affected family members, with at least one parent and child affected.
Autosomal recessive inheritance pattern: For autosomal recessive disorders, the affected individual must have two abnormal gene (alleles). Thus, the affected individual inherits one abnormal allele from one parent and one abnormal allele from the other parent. Usually in these conditions, the mother is a carrier, has one mutated allele, and is unaffected. Similarly, the father also is a carrier, has one mutated allele, and is unaffected. Thus, in autosomal recessive disorders, both parents are usually unaffected carriers, and one or more children may be affected. In autosomal recessive disorders, there are many less affected individuals in the family - usually just one child is affected, sometimes 2.
X-linked inheritance pattern: X-linked disorders involve genes that are on the X chromosome. Females have two X chromosomes, and men have one X chromosome. Thus, men have only one copy of genes that are on the X chromosome. When there is a gene with a mutation (mistake) on the X chromosome, females who have the mutation will have it on one X chromosome, and the other will be normal. Thus, females are unaffected or mildly affected because they have one abnormal gene and one normal gene that compensates. The female children of a female carrier will have one normal X chromosome from the father. If they inherit the abnormal allele on the X chromosome from the mother, they will be carriers like the mother. The son of an affected female will have a normal Y chromosome from the father. If the son inherits the mutant allele from the mother, he will have one mutated gene and will have the disease. If he inherits the normal allele from the mother, he will not have disease. Thus, individuals with X-linked disease will affect men predominantly, and women will usually be unaffected. In some X-linked diseases, women may be mildly affected.
Nonspecific inheritance pattern: Sometimes it is difficult to tell the inheritance because some family members may be mildly affected and thought not to have the disease.
What are the characteristics of the urine?
It is extremely important to know for each affected family member if there is a history of blood in the urine (seen under the microscope - usually not just by looking at the urine) or protein in the urine. This helps doctors to identify what group of diseases are present.
The following table shows examples of diseases according to inheritance pattern:
Symptoms of Inherited Kidney Disease
Common symptoms associated with inherited kidney disease include hearing or vision problems, gout, anemia, a solitary kidney or problems with kidney drainage. These can be clues to diagnosis.
How Can I Find a Diagnosis For My Family?
- A good first step is to classify the conditions as described above and put together a family tree that lists affected individuals and ages that they needed dialysis or a kidney transplant. It is useful to talk personally to as many family members as possible with the condition. Who is their doctor? What diagnoses were they given?
- Determine if any family members have undergone genetic testing and try to obtain a copy of the results for your doctor
- Determine if any families have ever undergone a kidney biopsy to make a diagnosis. If a biopsy has been done, obtain a copy of the report
- When you go to your kidney doctor, make sure to bring as much information as possible and make sure to tell your doctor about your family history. Many kidney doctors fail to ask about a family history.
- Make use of various Internet sites to help find a diagnosis. It is important to start your search with key words that include the type of inheritance and the urinary findings, as well as any other features of the disease.
We are very interested in helping identify the cause of inherited kidney disease for families in whom the cause is unknown. We have helped over 400 families identify the cause of kidney disease in their family. If you have an inherited kidney disease and do not know the cause, please feel free to contact us at [email protected].