Nail–patella syndrome

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Nail–patella syndrome
Synonyms	Hereditary onycho-osteodysplasia (HOOD), Fong disease
Pronounce
Specialty	Medical genetics
Symptoms	Nail dysplasia, absent or underdeveloped patellae, elbow abnormalities, iliac horns
Complications	N/A
Onset	Congenital
Duration	Lifelong
Types	N/A
Causes	Genetic mutation in the LMX1B gene
Risks	Family history
Diagnosis	Clinical diagnosis, genetic testing
Differential diagnosis	Osteogenesis imperfecta, Ehlers-Danlos syndrome
Prevention	None
Treatment	Symptomatic management
Medication	Pain management
Prognosis	Generally good with management
Frequency	1 in 50,000 individuals
Deaths	Rarely life-threatening

Nail–patella syndrome (NPS), also known as hereditary onycho-osteodysplasia, is a rare genetic disorder that affects the development of the nails, bones, and other parts of the body. It is an autosomal dominant condition, meaning that only one copy of the altered gene is necessary to cause the disorder. The syndrome is caused by mutations in the LMX1B gene, which plays a crucial role in the development of various tissues.

Signs and Symptoms

Individuals with Nail–patella syndrome typically exhibit a range of symptoms, which can vary widely in severity. Common features include:

• Abnormalities of the nails, such as underdeveloped, split, or absent nails.
• Skeletal abnormalities, particularly affecting the kneecaps (patellae), which may be small, irregularly shaped, or completely absent.
• Elbow abnormalities, including limited range of motion and underdeveloped or absent radial heads.
• Iliac horns, which are bony projections on the pelvis that can be detected through X-ray.
• Kidney involvement, which can lead to proteinuria and, in severe cases, renal failure.
• Eye abnormalities, such as glaucoma and Lester's sign (a pigmentation of the eye).

Genetics

Nail–patella syndrome is caused by mutations in the LMX1B gene located on chromosome 9q34. The LMX1B gene encodes a transcription factor that is essential for the proper development of the limbs, kidneys, and eyes. The condition follows an autosomal dominant inheritance pattern, meaning that an affected individual has a 50% chance of passing the mutation to their offspring.

Diagnosis

Diagnosis of Nail–patella syndrome is based on clinical evaluation, family history, and genetic testing. The presence of characteristic physical features, such as nail and patella abnormalities, can lead to a clinical diagnosis. Genetic testing can confirm the diagnosis by identifying mutations in the LMX1B gene.

Treatment

There is no cure for Nail–patella syndrome, and treatment is symptomatic and supportive. Management may include:

• Physical therapy to improve joint function and mobility.
• Pain management for joint discomfort.
• Regular monitoring of kidney function to detect and manage renal complications.
• Ophthalmologic evaluations to monitor and treat eye abnormalities.

Prognosis

The prognosis for individuals with Nail–patella syndrome varies depending on the severity of symptoms and the presence of complications, particularly those affecting the kidneys. With appropriate management and monitoring, many individuals can lead relatively normal lives.

See also

• Genetic disorder
• Autosomal dominant
• LMX1B
• Kneecap
• Proteinuria
• Renal failure
• Glaucoma

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