Nail–patella syndrome is a
genetic disorder
A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...
that results in small, poorly developed
nails and kneecaps, but can also affect many other areas of the body, such as the elbows, chest, and hips. The name "nail–patella" can be very misleading because the syndrome often affects many other areas of the body, including even the production of certain proteins.
[Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. .] Those affected by NPS may have one or more affected areas of the body, and its severity varies depending on the individual. It is also referred to as iliac horn syndrome, hereditary onychoosteodysplasia (HOOD syndrome), Fong disease or Turner–Kieser syndrome.
[James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). Saunders. Page 786-7. .]
Diagnosis of NPS can be made at birth but is common for it to remain undiagnosed for several generations. While there is no cure available for NPS, treatment is available and recommended.
Signs and symptoms
The skeletal structures of individuals who have this disorder may have pronounced deformities. As reported by several medical doctors, the following features are commonly found in people who with nail–patella syndrome:
Bones and joints
![Posterior iliac horn](https://upload.wikimedia.org/wikipedia/commons/d/d6/Posterior_iliac_horn.jpg)
* Patellar involvement is present in approximately 90% of patients; however, patellar aplasia occurs in only 20%.
* In instances in which the patellae are smaller or luxated, the knees may be unstable.
* The elbows may have limited motion (e.g., limited pronation, supination, extension).
* Subluxation of the radial head may occur.
* Arthrodysplasia of the elbows is reported in approximately 90% of patients.
* General hyperextension of the joints can be present.
* Exostoses arising from the posterior aspect of the iliac bones ("iliac horns") are present in as many as 80% of patients; this finding is considered pathognomonic for the syndrome.
* Other reported bone changes include scoliosis, scapular hypoplasia, and the presence of cervical ribs.
File:Nail-patella syndrome (NPS) Elbow1.JPG, An elbow of a man with nail–patella syndrome (NPS)
File:Nail-patella Elbow2.JPG, This is a view from a different angle of the same man's other elbow
Glaucoma is also closely associated with nail-patella, specifically open-angled glaucoma (OAG). Side affects may include frequent headaches, blurred vision, or total vision loss. This occurs gradually over time and symptoms may not be evident in children.
Kidney issues may arise such as
deposition of protein in the urine and nephritis. Proteinuria is usually the first sign of kidney involvement. It can reveal itself either rapidly or years after having asymptomatic deposition of protein in the urine,
kidney failure
Kidney failure, also known as end-stage kidney disease, is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney failure is classified as eit ...
occurs in around 5% of NPS patients.
Hypothyroidism
Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormone. It can cause a number of symptoms, such as po ...
,
irritable bowel syndrome
Irritable bowel syndrome (IBS) is a "disorder of gut-brain interaction" characterized by a group of symptoms that commonly include abdominal pain and or abdominal bloating and changes in the consistency of bowel movements. These symptoms may ...
,
attention deficit hyperactivity disorder
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inap ...
(ADHD), and thin tooth enamel are associated with NPS, but whether these are related or simply coincidences are unclear.
Genetics
![Autosomal dominant - en](https://upload.wikimedia.org/wikipedia/commons/4/4e/Autosomal_dominant_-_en.svg)
Nail–patella syndrome is inherited via
autosomal dominancy linked to aberrancy on human
chromosome 9
Chromosome 9 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome, as they normally do with all chromosomes. Chromosome 9 spans about 138 million base pairs of nucleic acids (the building blocks of D ...
's q arm (the longer arm), 9q34. This autosomal dominancy means that only a single copy, instead of both, is sufficient for the disorder to be expressed in the offspring, meaning the chance of getting the disorder from an affected heterozygous parent is 50%. The frequency of the occurrence is 1/50,000. The disorder is linked to the
ABO blood group locus
Locus (plural loci) is Latin for "place". It may refer to:
Entertainment
* Locus (comics), a Marvel Comics mutant villainess, a member of the Mutant Liberation Front
* ''Locus'' (magazine), science fiction and fantasy magazine
** ''Locus Award' ...
.
It is associated with random mutations in the
LMX1B
LIM homeobox transcription factor 1-beta, also known as LMX1B, is a protein which in humans is encoded by the ''LMX1B'' gene.
Function
LMX1B is a LIM homeobox transcription factor
In molecular biology, a transcription factor (TF) (or s ...
gene. Studies have been conducted and 83 mutations of this gene have been identified.
Diagnosis
The hallmark features of this syndrome are poorly developed fingernails, toenails, and patellae (kneecaps). Sometimes, this disease causes the affected person to have either no thumbnails or a small piece of a thumbnail on the edge of the thumb. The lack of development or complete absence of fingernails results from the loss of function mutations in the LMX1B gene. This mutation may cause a reduction in dorsalising signals, which then results in the failure to normally develop dorsal specific structures such as nails and patellae.
Other common abnormalities include elbow deformities, abnormally shaped pelvic (hip) bones, and kidney disease.
Treatment
Treatment for NPS varies depending on the symptoms observed.
* Perform screening for kidney disease and glaucoma, surgery, intensive physiotherapy, or genetic counseling.
*
ACE inhibitor
Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of hypertension, high blood pressure and heart failure. They work by causing relaxation of blood vessels as well as a decrease i ...
s are taken to treat
proteinuria
Proteinuria is the presence of excess proteins in the urine. In healthy persons, urine contains very little protein; an excess is suggestive of illness. Excess protein in the urine often causes the urine to become foamy (although this symptom ma ...
and
hypertension
Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
in NPS patients.
*
Dialysis and
kidney transplant
Kidney transplant or renal transplant is the organ transplant of a kidney into a patient with end-stage kidney disease (ESRD). Kidney transplant is typically classified as deceased-donor (formerly known as cadaveric) or living-donor transplantati ...
.
* Physical therapy, bracing and
analgesic
An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...
s for joint pain.
See also
*
List of cutaneous conditions
Many skin conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against t ...
*
References
External links
GeneReview/NCBI/NIH/UW entry on nail–patella syndrome
{{DEFAULTSORT:Nail-Patella Syndrome
Syndromes affecting the kidneys
Rare diseases
Conditions of the skin appendages
Autosomal dominant disorders
Transcription factor deficiencies
Patella
Syndromes affecting bones