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 chromosome 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. . The severity of these effects 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 Patella radiograph in Nail Patella Syndrome

Patella radiograph in Nail Patella Syndrome

* 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 Scoliosis (: scolioses) is a condition in which a person's Vertebral column, spine has an irregular curve in the coronal plane. The curve is usually S- or C-shaped over three dimensions. In some, the degree of curve is stable, while in others ...

, scapular hypoplasia, and the presence of

cervical ribs Cervical ribs are the ribs of the neck in many tetrapods. In most mammals, including humans, cervical ribs are not normally present as separate structures. They can, however, occur as a pathology. In humans, pathological cervical ribs are usually no ...

. 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 File:Nail-patella.jpg, link=, alt= Glaucoma is also closely associated with nail-patella, specifically open-angled glaucoma (OAG). Side effects 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 renal failure or end-stage renal disease (ESRD), 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 fa ...

occurs in around 5% of NPS patients.

Hypothyroidism Hypothyroidism is an endocrine disease in which the thyroid gland does not produce enough thyroid hormones. It can cause a number of symptoms, such as cold intolerance, poor ability to tolerate cold, fatigue, extreme fatigue, muscle aches, co ...

irritable bowel syndrome Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by a group of symptoms that commonly include abdominal pain, 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 symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple con ...

(ADHD), and thin tooth enamel are associated with NPS, but whether these are related or simply coincidences are unclear.

Genetics

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 DN ...

'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 The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes (red blood cells). For human blood transfusions, it is the most important of the 47 different blood type (or group) cla ...

locus Locus (plural loci) is Latin for "place". It may refer to: Mathematics and science * Locus (mathematics), the set of points satisfying a particular condition, often forming a curve * Root locus analysis, a diagram visualizing the position of r ...

. 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 domain, LIM homeobox transcription factor which plays a central role in Limb development#Dor ...

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, kidney disease, and abnormally shaped pelvic (hip) bones.

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 high blood pressure and heart failure. This class of medicine works by causing relaxation of blood vessels as well as a decr ...

s are taken to treat

proteinuria Proteinuria is the presence of excess proteins in the urine. In healthy persons, urine contains very little protein, less than 150 mg/day; an excess is suggestive of illness. Excess protein in the urine often causes the urine to become fo ...

and

hypertension Hypertension, also known as high blood pressure, is a Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not cause symptoms i ...

in NPS patients. *

Dialysis Dialysis may refer to: * Dialysis (chemistry), a process of separating molecules in solution **Electrodialysis, used to transport salt ions from one solution to another through an ion-exchange membrane under the influence of an applied electric po ...

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 transplantat ...

. * Physical therapy, bracing and

analgesic An analgesic drug, also called simply an analgesic, antalgic, pain reliever, or painkiller, is any member of the group of drugs used for pain management. Analgesics are conceptually distinct from anesthetics, which temporarily reduce, and in s ...

s for joint pain.

References

External links