Nephronophthisis (NPHP) begins in early life, usually affecting babies and young children. Before birth The first signs of NPHP may be detected during the growth (antenatal) ultrasound scans of babies, routinely performed at the 18th week of pregnancy. These scans may show bright kidneys or kidneys containing a number of cysts. However, the kidneys may also appear normal. In the womb, the baby is normally surrounded and protected by a watery fluid – the amniotic fluid. This fluid is made by the baby’s kidneys and is in fact very dilute urine. With NPHP, the baby’s kidneys sometimes do not produce enough amniotic fluid. This can be seen on an antenatal scan. Newborn babies NPHP can affect a baby’s kidneys in different ways. They may be poorly developed with small cysts or be enlarged kidneys so that the baby’s tummy looks swollen and the kidneys can be felt during a physical examination. An ultrasound scan may show that the kidneys contain many small cysts, a key feature of the diagnosis. Blood tests may show that kidney function is already low. Children Children with NPHP often have excessive thirst, preferring water to food. Partly because of this, they risk poor nutrition and reduced growth. Bed-wetting is common in school-aged children due to increased urine production. Kidney function can decline and dialysis may be needed. High blood pressure may also develop. Children with NPHP should therefore have regular blood pressure tests so that this is picked up and treated before it causes problems. Adults Although usually diagnosed in childhood, NPHP can sometimes go undetected for decades and present later in life as kidney failure.
As yet there are no treatments that can reverse or slow the progression of NPHP. Treatment is therefore aimed at controlling symptoms and should be managed by a specialist center with expertise in this disease and availability of various specialists working as a team. Individual assessment is extremely important, as the disease presents in various combinations of other organ involvement and severity. Regular blood tests are needed to find out the exact level of kidney function. This is described as Stages of Chronic Kidney Disease (CKD). Children with mild kidney problems (CKD stages 1-3) may only need simple treatment and regular monitoring by a kidney specialist. This may involve adjustments to the diet and nutritional supplements, as well as regular checks on blood pressure. Advanced kidney failure (CKD stages 4-5) will need to be treated by dialysis or transplantation. Occasionally the kidneys are so enlarged that one or other may have to be removed to make space in the abdomen for comfort and for feeding.
here are various active patient support groups in the UK and beyond. The following websites are a useful resource for anyone wanting to know more about the help and support available. www.ciliopathyalliance.org www.jsrdf.org www.lmbbs.org.uk www.alstrom.org.uk/ciliopathy There is also a very active Facebook group that users can request to join.
Nephronophthisis is a form of renal ciliopathy – genetic conditions that affect the cilia – tiny hair-like structures on the surface of the cells that help with transmitting messages. In ciliopathy, these cilia are abnormal so signaling between and within the cells does not work as it should. In the kidneys this may lead to cyst formation or large areas of scarring (fibrosis). These affect the proper functioning of the kidney. In the long term this can reduce the function of the kidney and eventually lead to kidney failure. How is it inherited? Most types of ciliopathy are inherited conditions, caused by a genetic alteration in the genes that are involved in the normal development and functioning of the cilia. Everyone has two copies of these genes – one from each of our parents. Ciliopathies such as NPHP usually occur when both parents pass on a copy of a mutated gene to their child. Boys and girls are affected equally. This pattern is called autosomal recessive inheritance. The parents of affected children do not have the disease themselves because they each have one normal copy of the gene which overcomes the effect of the mutated one. They are therefore known as carriers of the condition. If both parents are carriers, then the chances of a child receiving two faulty genes, one from each parent, is 1 in 4 (or 25%). If the child receives only one copy of the mutated gene, then they will be unaffected by the condition but will be a carrier of the disease just like their parents. This diagram shows how this condition can be passed on to the children of two carrier parents.
Genetic testing can be helpful. It is usually offered when there are grounds to suspect that parents are carriers of the mutated gene, for example when an ultrasound scan during pregnancy suggests ciliopathy conditions or if a couple already has a child with the condition. Currently not all mutations are identifiable due to the complexity of the genes and various unknown mutations. Testing is becoming more reliable with improvements in genetic techniques. Antenatal counselling provides an opportunity to discuss options about the future of a pregnancy. When both parents are confirmed carriers of a known gene mutation, it is possible to discuss pre-natal and/or pre-implantation genetic diagnosis (PGD). In this technique, embryos are tested during a cycle of in vitro fertilization (IVF) and only unaffected embryos are transferred into the mother’s womb to enable the birth of a child without the condition.
The ARPKD/NPHP Rare Disease Group (RDG) is working with international partners with the aim of finding new and improved treatments and to empower patients. A first step is to compile the symptoms, treatments used and markers of ciliopathies such as NPHP. To do this the RDG is registering patients with NPHP in the National Renal Rare Disease Registry (RaDaR).The database will be used to find suitable participants for future research trials into the effectiveness of new treatments. If you are interested in finding out more about the registry RaDaR or the activity of the RDG please visit the ARPKD/PHP RDG page.