Nail patella syndrome is a rare genetic condition that can cause problems with the nails, bones and kidneys.
Almost everyone with nail patella syndrome has abnormal nails, and many people also have problems with their knee caps (patellae), elbows and pelvis.
Some of the problems will be obvious from birth, but others may not become apparent until later on.
There are several symptoms and problems associated with nail patella syndrome.
Nails may be missing, underdeveloped, discoloured, split, ridged or pitted.
Thumbnails are most severely affected, with each fingernail being less severely affected from the index finger to the little finger.
Toenails are usually less affected by the condition.
The kneecaps may be missing, small, irregularly shaped and easily dislocated, and can click, lock or may feel unstable or painful.
Some people aren't able to fully extend their arms or turn their palms up while keeping their elbows straight. The elbows may also angle outwards, and dislocations can occur.
Bony growths on the pelvic bone (visible on X-rays) are common, but don't usually cause problems.
People with nail patella syndrome may also have:
Nail patella syndrome is usually caused by a fault in a gene called LMX1B that's inherited from one parent.
But there isn't always a family history of nail patella syndrome. In some cases, an LMX1B gene mutation (alteration) occurs for the first time on its own.
Nail patella syndrome is usually diagnosed based on your or your child's symptoms. In most cases, a blood test to check for the faulty gene can confirm the diagnosis.
In about 5% of people diagnosed with nail patella syndrome, a fault in the LMX1B gene can't be found.
If you have nail patella syndrome, there's a 1 in 2 (50%) chance that any child you have will be born with the condition.
If you're planning to have a baby, talk to your GP about getting a referral to a genetic counsellor. They can explain the risks and what your options are.
These may include:
PGD is similar to in vitro fertilisation (IVF), but the embryos are tested to check that they don't have the faulty gene before they're implanted in the womb.
The Human Fertilisation and Embryology Authority (HFEA) has more information about PGD.
There's no cure for nail patella syndrome, but treatments are available to help manage the symptoms.
If your kneecaps are easily dislocated and painful, painkillers, physiotherapy, splinting and bracing may help.
But the long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) should be avoided because they can affect the kidneys.
Some people may need corrective surgery for problems with the bones and joints. This should be carried out after an MRI scan by a surgeon who understands the condition.
Urine tests should be carried out at birth to check for kidney problems. High levels of protein in the urine may need to be treated with medication.
Later on, your urine and blood pressure should be tested every year.
Kidney problems may occur during (or be made worse by) pregnancy in women who have nail patella syndrome.
It's recommended that pregnant women with the condition have their blood pressure taken and urine tested frequently.
If your kidneys aren't working properly, you may need dialysis, where a machine is used to replicate many of the kidney's functions.
If you have severe kidney disease, you may need a kidney transplant.
Screening for glaucoma should start as soon as a child is able to co-operate with the examination.
Treatment for glaucoma may involve using eye drops or having a procedure to reduce the pressure inside the eye.
A dental examination should be carried out at least every 6 months.
An assessment of bone density is recommended for young adults to check for osteoporosis.
If you or your child has nail patella syndrome, your clinical team may pass information on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).
This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.