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Nail-Patella Syndrome

Nail Patella Syndrome

Nail-Patella Syndrome (NPS) is a rare autosomal dominant disorder that affects nails and bones. Some individuals have mild presentations while others experience serious renal and ocular complications. 


Presentation

NPS is either present at birth or in early childhood. The features of the disease vary from one person to another. 

Nails

Nail changes are observed in most patients and are usually bilateral [5]. The most commonly involved fingernails are on the first, third, and fifth digits. Furthermore, the thumbnail deformity is more prominent than the others. Specifically, the nails are characteristically small, narrow, thin or thick, ridged, split and possibly discolored. Most cases feature a malformed lunula with a characteristic triangle shape. In contrast to fingernails, the toenails are less affected.

Bones

A majority of patients with NPS exhibit bone abnormalities in the patella. Specifically, one or both patellas are either absent, abnormally small, hypoplastic, or shaped incorrectly [8]. Additionally, the patella may be displaced laterally and superiorly. Knee manifestations are seen in 74% of affected patients according to one study [5].

Other lower extremity bones may also have deformities. Hypoplasia of the fibula and femur causes subluxation or partial dislocation of the knee, which contribute to the restriction of movement. Moreover, patients exhibit genu varum, or "bow-leg" of the affected leg(s). This condition may result in complications such as progressive bone degeneration, knee pain, stiffness, and osteoarthritis.

Elbow involvement is also common in patients with NPS [5]. The deformities are seen in the head of the radius and capitellum of the humerus, of which either can be small and hypoplastic. Some also have webbing of the skin at the antecubital region of the elbow. These patients exhibit a limited range of movement in arm extension, pronation, or supination as well as subluxation. 

In affected hipbones, abnormal projections arise from the superior portions of the bilateral iliac horns. In fact, this is pathognomonic of the disease [5] and can be seen on fetal ultrasound [9]. It is can also be observed on X-rays in affected babies and children. Other skeletal features are scapular hypoplasia, scoliosis, and pectus excavatum [5].

Eyes

Glaucoma is a potentially serious clinical manifestation that occurs secondary to fluid blockage. With increasing fluid pressure, patients may experience headaches, blurry vision, and other visual problems. This condition may progress to loss of peripheral vision and blindness. Other eye abnormalities include the hyperpigmentation of the pupillary margin of the eye called Lester’s sign [5]. In addition, cataracts and microcornea could develop.

Kidneys

Nephropathy, which may present in childhood or later stages, is demonstrated in approximately 30% to 40% of patients. This manifestation is attributed to the degeneration of renal tubules and/or glomeruli. Hence, nephrotic and/or glomerular disease develop.

The first clinical signs of nephropathy are hematuria, hypertension, and possibly edema. While kidney disease could be benign, it has the potential to progress to renal failure. In those with nephropathy, they may develop nephrotic syndrome. Some progress to kidney failure but this is less likely to occur before the fourth decade of life.

Other

There are neurologic symptoms in NPS such as numbness, tingling, and burning sensations represented in a glove and stocking pattern. Furthermore, epilepsy has been reported in a small percentage of patients [5]. Vasomotor symptoms due to poor circulation such as Raynaud’s phenomenon may be present. Also, patients can experience gastrointestinal problems such as constipation and irritable bowel syndrome. Often the former is seen in infancy [5]. Finally, dental issues may arise resulting in weak teeth and thin enamel. The overall general appearance of these individuals is depicted by lean body with little muscle. These patients may have curved spines.

Short Stature
  • Laboratory screening for short stature and a GH stimulation test were normal. We present a child with proven NPS with short stature and hypothyroi dism. We did not find publications that described this triple association.[ncbi.nlm.nih.gov]
  • Common features include disproportionate short stature with short limbs, particularly rhizomelic shortening, true megalencephaly with hydrocephalus in a minority, midface hypoplasia, a trident hand configuration, and joint hyperextensibility.[doi.org]
  • stature and hypothyroidism in a child with Nail-Patella Syndrome.[malacards.org]
  • stature ( Aarskog-Scott syndrome , Cockayne syndrome , Cornelia de Lange Syndrome , Dubowitz syndrome , Noonan syndrome , Robinow syndrome , Silver-Russell dwarfism , Seckel syndrome , Smith-Lemli-Opitz syndrome ) limbs ( Adducted thumb syndrome , Holt-Oram[wikidoc.org]
Nail Abnormality
  • All patients had nail abnormalities (100%), the most frequent finding being hyponychia. Triangular lunulae were observed in four patients.[ncbi.nlm.nih.gov]
  • Case Details Subluxation of the radial head and bilateral patellar hypoplasia Answer Diagnosis: Nail-Patella Syndrome Also termed Hereditary Osteo-onychodysplasia and Fong syndrome Features: Nails: 80-90% of patients have nail abnormalities, with absent[pedsradiology.com]
  • Nail abnormalities are the characteristic feature of Nail-Patella Syndrome. In this condition, the nails may be entirely absent or not fully developed. They might even be discolored or split.[epainassist.com]
  • On further questioning, it was established that a first‐degree relative had nail abnormalities that were similar to the propositus. Fig. 1. Several dystrophic nails in nail‐patella syndrome. Fig. 1. Several dystrophic nails in nail‐patella syndrome.[ndt.oxfordjournals.org]
Respiratory Distress
  • One child had seizures on day 2 of life and both had significant respiratory distress. The features of these cases can be explained in the context of what we now know about mutations in FGFR3.[doi.org]
Brachydactyly
  • (D) There is generalised brachydactyly with a trident hand configuration. Developmental progress was normal with only the expected gross motor delay associated with achondroplasia. Cognitive function was normal.[doi.org]
Limitation of Elbow Movement
  • She was assessed for limitation of elbow movements at 3 weeks of age and underwent physiotherapy for thickened biceps tendon. She subsequently developed laxity of knees and ankles, and x-ray revealed absent patellae at 32 weeks.[ncbi.nlm.nih.gov]
Normal Stature
  • His father presented a similar phenotype with normal stature. His bone age was equivalent to his chronological age. Laboratory screening for short stature and a GH stimulation test were normal.[ncbi.nlm.nih.gov]
Hypoplastic Nails
  • The most common clinical findings are a hypoplastic patella, elbow dysplasia, iliac horns, and hypoplastic nails. Because renal and ophthalmologic complications are prevalent, the management of NPS is multidisciplinary.[journals.lww.com]
  • Clinically, the key feature is absent/hypoplastic nails from birth. Individuals may have flexion contractures and recurrent knee dislocations .[radiopaedia.org]
  • nails, bowed elbows, and nephrotic syndrome.[malacards.org]
Nail Deformity
  • Nail Patella Syndrome can usually be diagnosed with the naked eye, because there are obvious bone structure and nail deformalities. Pelvic bone mutations found in 80% of Nail Patella patients are not associated with any other disease.[torresbioclan.pbworks.com]
Kidney Failure
  • Development of symptomatic kidney failure is rare in this group, and proteinuria (present in approximately one-third) does not appear to be progressive.[ncbi.nlm.nih.gov]
  • Kidney failure is a concern among patients with this condition, and an early diagnosis is important to prolong the use of the kidneys. Early symptoms of kidney failure include blood in the urine. The skin can also be affected by this rare disorder.[brighthub.com]
  • About half of patients with NPS may have problems with their kidneys ranging from proteinuria (passing protein in the urine), to nephrotic syndrome (proteinuria and swelling), to kidney failure in about 3 per cent of people.[cafamily.org.uk]
  • However, in about 5% of those affected, progressive kidney failure may result, causing potentially life-threatening complications.[rarediseases.org]
Hematuria
  • Renal involvement occurs in 30-60% of patients and presents with proteinuria and/or microscopic hematuria, edema, hypertension.[ncbi.nlm.nih.gov]
  • Laboratory studies include urinalysis which reveals hematuria and proteinuria. Serum albumin measurement is important in nephrotic patients, in which hypoalbuminemia is demonstrated.[symptoma.com]
  • An early sign of kidney involvement is the presence of protein or blood in the urine (chronic, benign proteinuria and hematuria.) Kidney involvement is progressive, so early diagnosis and treatment of renal disease is important.[medical-dictionary.thefreedictionary.com]
  • Renal disease that manifests as proteinuria with or without hematuria occurs in 30-50% of patients, but progression to end-stage renal disease occurs in less than 5%.[emedicine.com]
Renal Insufficiency
  • Blood work revealed a creatine kinase of 389 U/L (normal, 175 U/L), renal insufficiency, anemia, and reduced calcium, phosphorus, and magnesium. Electrocardiogram showed complete heart block with an escape rhythm of 30/min.[ncbi.nlm.nih.gov]
  • Of these patients, 10% die of renal insufficiency. Both sexes are equally affected. The Cause of Nail Patella Syndrome Nail-patella syndrome has been recognized as an inherited disorder for over a hundred years.[steadyhealth.com]
  • . • 10% of the people die because of renal insufficiency. • ACE inhibitors are used to treat proteinuria and hypertension . Prevention The patients suffering with this disease should take the genetic concerns.[skin-diseases-and-skin-care.imedpub.com]
  • Laboratory tests may confirm certain findings that may indicate renal insufficiency, such as blood tests to check BUN and creatinine levels.[rarediseases.org]
  • Of these patients, 10% die of renal insufficiency. Patient Education Genetic counseling is recommended. Little EM. Congenital absence or delayed development of the patella. Lancet. 25 Sep. 1897. 150:781-784.[emedicine.medscape.com]

Workup

The workup includes a thorough physical exam, detailed patient and family history, imaging, and laboratory testing [8]. Fetal ultrasound can detect NPS prenatally with findings suggestive of characteristic limb abnormalities.

Imaging modalities can be utilized. Radiographs, CT, and/or MRI are used to identify bone abnormalities characteristic of NPS such as those found in the patella, radial head or ilium.

Laboratory studies include urinalysis which reveals hematuria and proteinuria. Serum albumin measurement is important in nephrotic patients, in which hypoalbuminemia is demonstrated. Additionally, a complete blood count will detect anemia if present. A combination of anemia, edema, and hypoalbuminemia is highly suspicious of nephrotic syndrome

A renal biopsy will display structural abnormalities that may be present even in asymptomatic patients [10]. Histologically, the findings include capillary wall thickening, collagen deposition, and focal and segmental sclerosis.

Microalbuminuria
  • Microalbuminuria was detected in 21.7% of subjects without overt proteinuria. Interestingly, nephropathy appeared significantly more frequent in females.[ncbi.nlm.nih.gov]

Treatment

Treatment of NPS consists of symptomatic and supportive measures. Patients with nephropathy are treated with ACE inhibitors for proteinuria. Also, a nephrology consult is indicated in these cases. Patients with open-angle glaucoma are treated the same as the general population. 

In some cases, physical therapy and other early orthopedic interventions are indicated such as knee replacement surgery and/or knee reconstruction. Also, elbow reconstruction surgery may be appropriate. Moreover, management of scoliosis may involve braces, casts or surgery.

Genetic counseling is beneficial in providing information and education for the patient and family members. Genetic screening may be offered, too. Clinicians should consider examination of family members.

NPS patients should undergo surveillance tests to monitor the progression of the disease. Yearly exams include [5]:

Further management includes monitoring scoliosis in children and adolescents. Caution with NSAIDS, longterm use may have damaging renal effects.

Prognosis

Patients with NPS generally lead ordinary lives but will need close monitoring and surveillance. Those with nephropathy that progresses to end-stage renal disease may require a transplant. Consequently, they do well afterwards.

Etiology

The etiology of NPS is due to mutations in LMX1B gene, which is a homeobox transcription factor that plays a significant role in the development of limbs, kidneys, and eyes. Specifically, this gene controls the dorsal-ventral pattern of embryological development [3] [4]. Approximately 80% of those with NPS inherited it from an affected parent. One study showed that 87.5% of NPS patients inherited the disorder while the remainder were sporadic. [5]. 

Epidemiology

The incidence of NPS is 22 per 1,000,000 population [6]. There is no gender preference in NPS. Abnormalities of nails, knees, and elbows are usually found at birth. However, patellar deformities are noted in childhood while renal manifestations can develop at any age. Also, glaucoma usually develops in adulthood.

Sex distribution
Age distribution

Pathophysiology

NPS occurs as a result of a mutated transcription factor. Various bones are affected such as the patella, ilium, radius, and humerus. Additionally, the nails are affected. Severe features include nephropathy and glaucoma [7]. Approximately 30% to 55% develop nephropathy [5] and about 5% of those with nephropathy progress to end-stage renal failure. It is thought that pathogenic variants of the LMX1B genes may be linked to proteinuria

Prevention

This disease cannot be avoided since it is genetic. However, renal problems and eye abnormalities such as glaucoma could be prevented with close surveillance. Hence, it is paramount for the patient to maintain close follow up with the medical team. Individuals with NPS and their family members may undergo genetic counseling and testing to learn about their chances of inheriting the disease and what NPS entails for future offspring.

Summary

Nail-Patella Syndrome (NPS), an autosomal dominant disorder, is characterized by a gene mutation in the transcription factor LMX1B, which results in deformity of nails and bones. Specifically, NPS affects bones in the knees, hips, and elbows. While some presentations are mild and benign, the sequelae vary from one individual to another [1] [2]. Complications include nephropathy and glaucoma.

Diagnosis is achieved through a comprehensive history and physical. Furthermore, it is pertinent to test for any renal or ocular disease through appropriate studies. Early identification of abnormalities results in more prompt treatment and delay of progression. Therefore, surveillance such as annual blood pressure measurement and studies assessing for proteinuria are highly recommended.

Therapy depends on the clinical picture. For individuals with bone deformities, physical therapy and surgical interventions may be indicated. Also, patients with nephropathy or glaucoma will be treated with appropriate medications. Most people commonly lead normal lives but should adhere to close follow up appointments with the medical team.

Patient Information

Nail-Patella Syndrome (NPS) is a disorder due to a mutated gene called LMX1B, which is involved in developing the limbs. NPS is an autosomally dominant disease. This means that one of the parents has a copy of the mutated gene and copy of the good gene. Therefore, there is a 50% chance of passing it to a child. 

This disease affects nails, bones and may even cause problems with kidneys and eyes. Usually, the presentation is at birth. Other cases present in childhood or later. Some individuals will have mild symptoms and signs while others may have more serious ones. The features are:

Nails

  • Nails are usually small, ridged, split, thickened, discolored or may be completely absent. 
  • Abnormal nails are most commonly found on the thumbs, index, and middle fingers. 

Bones

  • One or both patellas (kneecaps) may be abnormal, they could be too small or irregularly shaped.
  • Patella may be dislocated and deformed or even absent in one or both legs. The legs may even be bow legged.
  • There is knee pain, instability, and possibly limited movement.
  • In affected elbows, there is the inability to extend the arm and the elbow may angle outwards.

Kidney                                                      

  • Some patients will have protein in their urine without any clinical symptoms. In a small percentage of patients, this may progress to serious problems such as kidney failure although it is rare. 

Eye

Neurological

Gastrointestinal

  • Commonly found symptoms are irritable bowel syndrome (IBS) or constipation.

Circulation

  • Some patiemts will feel cold hand and feet due to inadequate blood supply.

Diagnosis depends on a thorough medical history of the patient and the patient’s family members as well as a detailed exam of the patient. Certain signs of NPS such as hip bone abnormalities can be seen on prenatal ultrasound. Also, X-rays or other imaging can detect abnormalities.

Early intervention to provide support and physical therapy is also impotant. In addition, the patient will have regular follow up appointments. The doctor will monitor blood pressure and perform urine tests to check for protein. Children and adolescents are checked for scoliosis. Also recommended are dental exams twice a year and eye exams to check for glaucoma, cataracts, and other eye problems. Treatment is reserved for signs and symptoms. 

Genetic counseling for the affected individual and family is available and usually beneficial. This involves assessment and discussion of passing on the disorder to future offspring. Parents can make informed decisions under the guidance of a medical professional. Genetic testing may be offered as well. Overall patients live normal lives, but close follow up is the key. 

References

Article

  1. Beals RK, Eckhardt AL. Hereditary onycho-osteodysplasia (nail-patella syndrome). A report of nine kindreds. Journal of Bone Joint Surgery American Volume. 1969;51(3):505–16.
  2. Turner JW. An hereditary arthrodysplasia associated with hereditary dystrophy of the nails. Journal of American Medical Association. 1933;100(12):882–4.
  3. Chen H, Lun Y, Ovchinnikov D, et al. Limb and kidney defects in Lmx1b mutant mice suggest an involvement of LMX1B in human nail patella syndrome. Nature Genetics. 1998; 19(1):51–5.
  4. Vollrath D, Jaramillo-Babb VL, Clough MV, et al. Loss-of-function mutations in the LIM-homeodomain gene, LMX1B, in nail-patella syndrome. Human Molecular Genetics. 1998; 7(7):1091.
  5. Sweeney E, Fryer A. Nail patella syndrome: a review of the phenotype aided by developmental biology. Journal of Medical Genetics. 2003; 40(3):153–162.
  6. Looij BJ Jr, te Slaa RL, Hogewind BL, et al. Genetic counselling in hereditary osteo-onychodysplasia (HOOD, nail-patella syndrome) with nephropathy. Journal of Medical Genetics. 1988; 25(10):682.
  7. Lichter PR, Richards JE, Downs CA, et al. Cosegregation of open-angle glaucoma and the nail-patella syndrome. American Journal of Ophthalmology. 1997;124(4):506–15.
  8. Bennett WM, Musgrave JE, Campbell RA, et al. The nephropathy of the nail-patella syndrome. Clinicopathologic analysis of 11 kindred. American Journal of Medicine. 1973; 54(3):304.
  9. Feingold M, Itzchak Y, Goodman RM. Ultrasound prenatal diagnosis of the nail-patella syndrome. Prenatal Diagnosis. 1998; 18(3):854–6.
  10. Chan PC, Chan KW, Cheng IK, et al. Living-related renal transplantation in a patient with nail-patella syndrome. Nephron. 1988; 50(2):164–6.

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Last updated: 2019-07-11 20:58