Nail-patella syndrome is rare disease with a genetic cause. Despite its name, it doesn't affect only the nails but also the eyes, bones or kidneys. Its symptoms are varied and quite unpredictable, even people from the same family can have different degrees of severity.
Most people who suffer from the nail-patella syndrome will have nail problems, which is the most common effect of this condition. The nails can be too small or even completely absent in some cases. When they are developed, the nails will have various deformities such as splits, ridges or pits. It is more common in the fingernails than on toenails and the nails of the thumbs are usually the most vulnerable. Usually, it also causes the lunula to have a strange triangular shape instead of the normal crescent one.
Nail-patella syndrome often affects the bone structure as well. The skeleton of patients can have various issues, especially on the elbow, knees or hips. The patellae, or kneecaps, are undeveloped, deformed or can be completely missing. This makes then unstable and easily dislocated. The same thing happens with the elbows and makes it impossible for some people to straighten the arms or execute certain movements with the palms. Another possible effect is the so-called cubitus valgus, which is an unusual outward angle of elbows. Iliac horns are also a common problem, formed by abnormal growths from the pelvic iliac bones. In most cases, these growths are not visible and might only be detected on an x-ray scan, but some can be felt through the skin. Iliac horns are considered to be a trademark of this disease, since they are almost never caused by any other condition.
The nail-patella syndrome can also affect the kidneys, eyes and other parts of the body. The nail-patella syndrome greatly increases the risk of glaucoma, which is a higher than normal eye pressure. The disease can make glaucoma start earlier than normal. On the kidneys, the nail-patella syndrome can eventually lead to their failure.
The nail-patella syndrome is known for having unpredictable symptoms that vary from one person to another. Some people who suffer from it don't have any symptoms at all. Some of them only become aware of it after genetic testing, for example studies done to establish family history.
The fingernails are usually the most obvious sign of the nail-patella syndrome. They can be deformed, undeveloped or simply missing. Almost all of the kids who suffer from nail-patella syndrome have abnormal nails of some kind. It is rare for all fingernails to be affected, usually only some of them are deformed. The nails on the thumbs and index fingers have the highest risk to be abnormal. By contrast, the pinky fingernail is usually normal. The condition can also affect toenails, but this is rare. Nails might be absent, smaller than normal, with an unusual color or a surface covered by splits, ridges and pits.
The second most common symptom of the disease is an abnormal kneecap, which is found in more than 90% of all kids affected by the nail-patella syndrome. It can affect only one kneecap or both of them. The kneecap can be missing or with a deformed shape, which causes constant dislocation. Due to the unusual shape, knees of patients sometimes appear to be square. The entire structure of the knee can also be affected, for example the bones, tendons or ligaments. These issues make walking very difficult or even impossible in some cases. Other bones can also be affected by the nail-patella syndrome. The most vulnerable to deformities are the feet and the hips.
Between 30 and 50% of people with nail-patella syndrome also experience kidney problems. These can sometimes start in childhood but are more common during adult life. In most cases, kidney diseases begin after the age of 30.
The nail-patella syndrome can cause eye problems as well, but the symptoms are varied. Doctors suspect that it blocks the flow of a fluid known as aqueous humor from the frost part of the eyes, which is a disease named open-angle glaucoma in medical terms. The syndrome sometimes leads to eyes that have more than one color. Other possible problems are astigmatism, cataracts and an abnormal development of the cornea.
Since the nail-patella syndrome is a genetic disease, it can't be treated directly. The only thing doctors can do is to address every symptom separately. All of the available therapies are symptomatic and only aim to support the patient. Bone surgery can correct abnormal joints and restore mobility in many cases. The elbow is rarely subjected to surgery but the knees, feet and ankles can usually be fixed. Kidney problems are treated just like other similar conditions, using hemodialysis or peritoneal dialysis. In severe cases of renal insufficiency, a transplant is also possible.