Nail-patella syndrome is characterized by abnormalities of the nails, knees, elbows, and pelvis. The features of nail-patella syndrome vary in severity between affected individuals, even among members of the same family.
Nail abnormalities are seen in almost all individuals with nail-patella syndrome. The nails may be absent or underdeveloped and discolored, split, ridged, or pitted. The fingernails are more likely to be affected than the toenails, and the thumbnails are usually the most severely affected. In many people with this condition, the areas at the base of the nails (lunulae) are triangular instead of the usual crescent shape.
Individuals with nail-patella syndrome also commonly have skeletal abnormalities involving the knees, elbows, and hips. The kneecaps (patellae) are small, irregularly shaped, or absent, and dislocation of the patella is common. Some people with this condition may not be able to fully extend their arms or turn their palms up while keeping their elbows straight. The elbows may also be angled outward (cubitus valgus) or have abnormal webbing. Many individuals with nail-patella syndrome have horn-like outgrowths of the iliac bones of the pelvis (iliac horns). These abnormal projections may be felt through the skin, but they do not cause any symptoms and are usually detected on a pelvic x-ray. Iliac horns are very common in people with nail-patella syndrome and are rarely, if ever, seen in people without this condition.
Other areas of the body may also be affected in nail-patella syndrome, particularly the eyes and kidneys. Individuals with this condition are at risk of developing increased pressure within the eyes (glaucoma) at an early age. Some people develop kidney disease, which can progress to kidney failure.
The prevalence of nail-patella syndrome is estimated to be 1 in 50,000 individuals.
Mutations in the LMX1B gene cause nail-patella syndrome. The LMX1B gene provides instructions for producing a protein that attaches (binds) to specific regions of DNA and regulates the activity of other genes. On the basis of this role, the LMX1B protein is called a transcription factor. The LMX1B protein appears to be particularly important during early embryonic development of the limbs, kidneys, and eyes. Mutations in the LMX1B gene lead to the production of an abnormally short, nonfunctional protein or affect the protein's ability to bind to DNA. It is unclear how mutations in the LMX1B gene lead to the signs and symptoms of nail-patella syndrome.
Nail-patella syndrome is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person inherits the mutation from one affected parent. Other cases may result from new mutations in the LMX1B gene. These cases occur in people with no history of the disorder in their family.
Other Names for This Condition
- Fong disease
- hereditary onycho-osteodysplasia
- hereditary osteo-onychodysplasia
- Osterreicher syndrome
- pelvic horn syndrome
- Turner-Kieser syndrome
Additional Information & Resources
Genetic Testing Information
Genetic and Rare Diseases Information Center
Research Studies from ClinicalTrials.gov
Scientific Articles on PubMed
- Bongers EM, Huysmans FT, Levtchenko E, de Rooy JW, Blickman JG, Admiraal RJ, Huygen PL, Cruysberg JR, Toolens PA, Prins JB, Krabbe PF, Borm GF, Schoots J, van Bokhoven H, van Remortele AM, Hoefsloot LH, van Kampen A, Knoers NV. Genotype-phenotype studies in nail-patella syndrome show that LMX1B mutation location is involved in the risk of developing nephropathy. Eur J Hum Genet. 2005 Aug;13(8):935-46. Citation on PubMed
- Marini M, Bocciardi R, Gimelli S, Di Duca M, Divizia MT, Baban A, Gaspar H, Mammi I, Garavelli L, Cerone R, Emma F, Bedeschi MF, Tenconi R, Sensi A, Salmaggi A, Bengala M, Mari F, Colussi G, Szczaluba K, Antonarakis SE, Seri M, Lerone M, Ravazzolo R. A spectrum of LMX1B mutations in Nail-Patella syndrome: new point mutations, deletion, and evidence of mosaicism in unaffected parents. Genet Med. 2010 Jul;12(7):431-9. doi: 10.1097/GIM.0b013e3181e21afa. Citation on PubMed
- McIntosh I, Dunston JA, Liu L, Hoover-Fong JE, Sweeney E. Nail patella syndrome revisited: 50 years after linkage. Ann Hum Genet. 2005 Jul;69(Pt 4):349-63. Citation on PubMed
- Sweeney E, Fryer A, Mountford R, Green A, McIntosh I. Nail patella syndrome: a review of the phenotype aided by developmental biology. J Med Genet. 2003 Mar;40(3):153-62. Citation on PubMed or Free article on PubMed Central
- Sweeney E, Hoover-Fong JE, McIntosh I. Nail-Patella Syndrome. 2003 May 31 [updated 2014 Nov 13]. In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2020. Available from http://www.ncbi.nlm.nih.gov/books/NBK1132/ Citation on PubMed