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Nail-Patella Syndrome
Sunday, 25 January 2004
Sunday, 25 January 2004
Hereditary Onychoosteodyplasia, Fong's disease, Iliac Horn Syndrome, Turner-Kieser syndrome

What

Nail-Patella Syndrome (NPS) is a rare genetic disorder that affects the bones, joints and connective tissue, as well as the kidneys and the eyes. The fingernails and specific bones in the knee and elbow may be misshapen or absent, and the kidneys may not work properly.

Who

Nail-Patella Syndrome occurs in all ethnic groups and equally in both males and females. NPS occurs in 1 in 50,000 live births and is most commonly inherited from parents who have the disorder. NPS is inherited in an autosomal dominant pattern, which means that one parent with the altered gene can pass it to a child 50% of the time with each pregnancy. However, in approximately 20% of cases, NPS is the result of a new change in the gene, meaning that it did not come from either parent and thus, there will not be a history of the disease in other family members.

Signs and Symptoms

As the name suggests, the most common abnormalities of NPS involve the nails and the patella (kneecap), but kidney, iliac bone (hip bone), eye and elbow abnormalities can also occur. Nail abnormalities occur in 80-100% of cases. The nails can be absent or hypoplastic, meaning they are about 30-50% of normal size. If the nails are affected, the thumbnail is always affected and the nails from the index finger to the little finger are progressively less damaged. The toenails can also be affected. The knee is affected in 60-100% of cases and the patella is absent in approximately 50% of cases. In other cases, the patella is smaller than normal size and/or the tendons and ligaments may be missing or attached incorrectly. These knee abnormalities can lead to knee instability. The iliac bones are affected in 80% of cases. The iliac bones will develop bony spurs or spines, usually on the back. There can occasionally be a club foot as well. Kidney disease develops in 30-50% of cases and varies in severity. It may present as proteinuria (losing protein in urine), but in some cases may progress to kidney failure that requires a kidney transplant. The most common eye abnormality is open angle glaucoma (blockage of fluid from the front chamber of the eye), but cataracts, dark coloration of the iris, small corneas and ptosis (droopy eyelid) can also occur. In persons with elbow involvement, they can often not fully straighten the elbow because the bones do not meet properly or the tendons and ligaments are misplaced.

Possible Causes

In Nail-Patella syndrome a specific gene, called LMX1B, is mutated. This gene is located on chromosome 9. This gene normally makes a protein called a transcription factor, which helps in the development of nails and patella and also in the proper placement of tendons and ligaments. This gene is also expressed in the eye and in the kidney. When this gene does not work properly, the abnormalities found in NPS are seen.

Diagnosis

NPS is usually diagnosed by the presence of some or all of the typical physical abnormalities which are investigated, particularly when there is a family history of the disease. X-rays and more sophisticated imaging, like CT scan or MRI, will help in defining the patella, iliac bone and elbow abnormalities. All patients with NPS or suspected NPS should have regular urine tests to look for proteinuria. In some cases, a kidney biopsy will be performed by a specialist in order to determine the severity of kidney disease. An ophthalmologist (eye specialist) can perform special tests to look for glaucoma or cataracts.

Treatment

There are many aspects of NPS and the opportunities for treatment and management vary. Surgery is sometimes an option for the skeletal abnormalities and physical therapy can be helpful with knee stability. Kidney disease is monitored closely and usually treated as symptoms arise and are troublesome. If the kidney completely fails, dialysis is necessary and, ultimately, kidney transplant is performed. Transplant is a good option since the kidney abnormalities do not recur in the transplanted kidney. However, abnormal nails may regrow after the transplant. Currently there is no cure for NPS, but research is ongoing.

Prognosis

The long-term course of NPS is variable. Some people have only mild symptoms, which do not affect their daily lives. Others have difficulty with exercise due to knee instability or other skeletal problems. Some children and adults, however, require a wheelchair due to more severe skeletal involvement. Kidney disease varies between mild protein in the urine without other physical symptoms to end stage renal disease requiring a transplant. When renal failure develops, it is usually in teenagers or young adults, but can also develop after years of asymptomatic proteinuria.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Nail Patella Syndrome Worldwide
Provides information for patients, parents and doctors about Nail-Patella syndrome, links to other sites and information about current research.

Nail Patella Syndrome
Website written by a woman with NPS. Provides information, pictures and links to other sites.

Nail Patella Syndrome
Provides information, pictures and links to information about genetic research.

Google Search for Nail-Patella Syndrome

References and Sources

Author unknown, Chapter 669: Disorders of the Nails – nail-patella syndrome and Chapter 701: Disorders involving Transcripton Factors, (2000). In Behrman RE, Kliegman RM, & Jenson HB (eds) Nelson Textbook of Pediatrics, 16th edition. WB Saunders, p. 2026, 2125. Tunnessen W, and Krowchuk D (1999). Chapter 116: Pediatric Dermatology, Brewer E, and Berry P (1999). Chapter 327: Glomerulonephritis and Nephrotic Syndrome, Powell D. Chapter 334: Nail-Patella Syndrome. In McMillan J, DeAngelis C, Feigin R, & Warshaw J (eds) Oski’s Pediatrics: Principals and Practice, 3rd edition. p. 727, 1598, 1607. www.nailpatella.org