Nail-patella syndrome
Synonyms and keywords:Iliac Horn syndrome; hereditary osteoonychodysplasia; Fong disease; Turner-Kiser syndrome

# Overview
Nail-patella syndrome (NPS) is a genetic disorder 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.:666  It is also referred to as iliac horn syndrome, hereditary onychoosteodysplasia, Fong disease or TurnerKieser syndrome..

# Historical Perspective
Chatelain first described the syndrome in 1820, and its genetics was first documented by Little in 1897.

# Pathophysiology

## Genetics
The Nail-Patella syndrome is inherited via autosomal dominancy  (see autosomal dominant) linked to aberrancy on human chromosome 9's q arm  (q stands for longer arm), 9q34.  This autosomal dominancy means that only a single copy, instead of both, is sufficient for disorder to be expressed in the offspring, meaning that the chance of getting the disorder from an affected parent is 50%. The frequency of the occurrence is 1/50,000. The disorder is linked to the ABO blood group locus.

# Differentiating Nail-patella syndrome from Other Diseases

# Epidemiology and Demographics
The prevalence of nail-patella syndrome is estimated to be 1 in 50,000 individuals.

# Diagnosis

## Symptoms
- Poorly developed fingernails, toenails, and patellae (kneecaps).
- The nails may be absent, pitted, rigged, discolored or a small piece of a thumbnail may be found on the edge of the thumb. The area at the base of the nail is triangular instead of usual crescent shape.
- Elbow deformities
- Some patients are unable to keep their elbow extended or keep their palms up with elbow extended
- Abnormally shaped pelvis bone (hip bone) or outgrowths causing no symptoms
- Knee may be small, deformed or absent
- Some research shows that people with NPS are more prone to glaucoma and scoliosis, due to poorly developed spines.

## Physical Examination

### Appearance of the Patient
- May have pronounced skeletal deformities

### Skin
- Nail changes:
Presentation varies from no thumbnail or small piece of a thumb nail at the edge of the finger to minor pitting or discoloration
- Presentation varies from no thumbnail or small piece of a thumb nail at the edge of the finger to minor pitting or discoloration

### Eyes
- Glaucoma

### Extremities
- Patellar apalsia may be seen
- Unstable knees from patellar subluxation
- Limited range of motion of elbow joint
- Arthodysplasia of the elbow joint may be present
- General hyper-extension of the elbow noted
- Exostosis from the iliac bones : pathognomic feature of the syndrome
- Scoliosis
- Scapular apalsia
- Cervical ribs may be present
- Subluxation of radial head

## Laboratory Findings

### Blood tests
- Raised serum creatinine
- Increased BUN
- Increased serum urea
- Decreased creatinine clearance

### Urinalysis
- Proteinuria

# Treatment
- Medical treatment:
Enalapril plus Losartan can help decrease proteinuria
No treatment is available for the dermatological manifestations of the disease
- Enalapril plus Losartan can help decrease proteinuria
- No treatment is available for the dermatological manifestations of the disease
- Surgical treatment:
Orthopedic correction for knee deformities
- Orthopedic correction for knee deformities