Nail-patella syndrome: symptoms, kidney checks, genetics and management

Nail-patella syndrome (NPS) is a rare genetic condition that can cause problems with the nails, the kneecaps (patellae), the elbows, the pelvis, the kidneys and the eyes. Contact, a UK charity for families with disabled children, notes that it is also known as Fong's disease, hereditary osteo-onycho-dysplasia and Turner-Kieser syndrome.

It is extremely variable, even between members of the same family. Some people have only minor nail changes and never know they have a problem, while others have a combination of joint and kidney problems. Some features are obvious from birth, while others only become apparent later on.

The information adapted from the NHS website by nidirect, and the clinical text from Contact written by a consultant clinical geneticist, list the main features.

• Nails: missing, underdeveloped, discoloured, split, ridged or pitted. Thumbnails are most severely affected, with each fingernail less affected from the index finger to the little finger, and toenails usually less affected.

• Kneecaps: they may be missing, small, irregularly shaped and easily dislocated, and can click, lock or feel unstable or painful. Dislocation of the patella is common, and there may be early arthritis of the knees.

• Arms and elbows: some people cannot fully extend their arms or turn their palms up with elbows straight. The elbows may angle outwards and dislocations can occur.

• Pelvis: bony growths (iliac horns) on the pelvic bone are visible on X-rays and are common but do not usually cause problems.

• Kidneys: protein in the urine, sometimes with blood, which can sometimes progress to kidney disease.

• Other: glaucoma at an early age, numbness or tingling in the hands and feet, poor circulation in the hands and feet, constipation or IBS, difficulty putting on weight, thin bones and back pain in adults.

NPS is usually caused by a fault in a gene called LMX1B, which is located on chromosome 9. The inheritance pattern is autosomal dominant: a person with the condition has a 1 in 2 (50 per cent) chance that any child will inherit it. The severity cannot be predicted, so a child may be more or less affected than the parent.

There is not always a family history. In some cases an LMX1B gene mutation occurs for the first time in the person affected. nidirect says that in about 5 per cent of people diagnosed with NPS, a fault in the LMX1B gene cannot be found.

NPS is usually diagnosed from the symptoms of the person or their child. The Contact text says the diagnosis is made by identifying common features during a clinical examination, and genetic testing is possible if required. nidirect says that in most cases a blood test to check for the faulty gene can confirm it.

The Contact text notes that bony changes such as pelvic horns and elbow differences can show on X-rays, which can support the clinical picture.

There is no cure, but treatments help manage symptoms, according to nidirect. The recommendations it lists are as follows.

• Kneecap and joint problems: painkillers, physiotherapy, splinting and bracing may help. Long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) should be avoided because they can affect the kidneys. Some people need corrective surgery, which should be done after an MRI scan by a surgeon who understands the condition.

• Kidneys: urine tests should be carried out at birth to check for kidney problems, and later urine and blood pressure should be tested every year. High levels of protein in the urine may need treatment with medication. Kidney failure, if it occurs, can be treated with dialysis or kidney transplantation, according to Contact.

• Pregnancy: kidney problems may occur or worsen during pregnancy, so blood pressure and urine should be checked regularly. Contact also notes an increased chance of pre-eclampsia.

• Eyes: screening for glaucoma should start as soon as a child can co-operate with the examination, and it can be treated with eye drops or a procedure to reduce eye pressure.

• Teeth and bones: a dental examination at least every 6 months, and a bone density assessment in young adults to check for osteoporosis.

nidirect advises that if you have NPS and are planning a baby, you should talk to your GP about a referral to a specialist who can explain the risks and options. These may include tests during pregnancy to see if the baby will have NPS, or pre-implantation genetic diagnosis (PGD), in which embryos are tested before being placed in the womb. Contact notes that most features of NPS would not be possible to detect on a prenatal ultrasound scan, and that it is not possible to predict how severely a baby would be affected.

Genetic counselling is a way to talk through these options without any pressure to choose one path over another.

The main long-term issues described in the sources are kidney health, eye pressure and joint function, which is why regular checks are recommended. Severity varies widely, so a specialist team is best placed to give an individual outlook.

Care in the UK is usually arranged through the NHS, with a GP referring to genetics, kidney, eye or orthopaedic and physiotherapy services as needed. The Contact text, last updated in 2012, says there was then no UK support group for NPS and that families could use Contact's helpline for advice and links to other families; this may have changed, so ask your clinical team about current support.