In the majority of people with Nail Patella Syndrome, the fingernails are partly or entirely missing (80-100% of cases). This is most severe on the thumb and decreases in severity toward the 5th finger. The crescent "moons" at the base of the nail are often triangular. Creases over the joint nearest the tip of the finger may be absent and fingers may seem double-jointed. The 5th finger may be slightly hooked (click here to see a picture). Toenails can also be affected but to a lesser degree than fingernails.
Knees:
Abnormality of the knee cap (patella) represents the second most common finding in NPS (60-100% of cases). In approximately half of the people, the patellae are completely absent, with various degrees of size reduction reported in the remainder. If present, the patella often slips to the outside when the knee is straightened. Some of the tendons and ligaments in the leg may be missing or attached incorrectly. (Click here to see a picture.)
Pelvis:
A feature unique to Nail Patella Syndrome is the presence of Iliac Horns in approximately 80% of the people. These boney projections are clearly visible on X-Ray, are sometimes palpable, but are asymptomatic. The shape of the pelvic bones may be slightly altered, leading to a sway-back appearance (lordodis).
Elbows:
Many people with Nail Patella Syndrome are unable to fully straighten their arms because the bones in the elbow joint do not meet properly. Tendon and ligaments may be misplaced and webbing sometimes forms around the elbow. (Click here to see a picture.)
Feet and Ankles:
Many children with NPS are born with club foot deformities due to misplacement of tendons around the foot and ankle. Although these may respond to physiotherapy, surgery may be required. Due to tight heel cords (Achilles Tendons) people with NPS may tend to walk on their toes.
The orthopedic findings in people with Nail Patella Syndrome can be interpreted as a loss of patterning across the dorso-ventral axis of the limb. Since the primary effect in the knee and elbow is mislocalization of tendons and ligaments, it is imperative that Magnetic Resonance Imaging (MRI), in addition to X-ray, be performed prior to surgery.
Kidney Disease:
The incidence of Kidney disease in NPS is approximately 30-50%. This is usually more apparent later in life, although there are reports of renal problems in childhood. The earliest sign is usually the presence of protein in the urine. Kidney disease is progressive and potentially fatal. People with NPS should have regular urinalysis to monitor changes in kidney function.
Eye Disease:
It has recently become apparent that open angle glaucoma is also part of NPS. Open angle glaucoma can be described as a condition caused by progressive blockage of the outflow of fluid from the front chamber of the eyes. If this is left untreated, the increase in fluid pressure results in permanent irreversible damage to the optic nerve.
People with NPS should have regular ophthalmologic examinations since the progression of glaucoma can be limited by treatment.
Genetics:
Although recognized as a hereditary disorder for over 100 years, the gene mutated in people with NPS, called LMX1B, was only identified in 1998. LMX1B encodes a transcription factor which is primarily involved in specification of dorsal-specific structures (such as nails and patellae) in the developing limb. The proper placement of tendons and ligaments within the limb also requires the proper expression of LMX1B. LMX1B is also expressed in the anterior chamber of the developing eye and in the kidney throughout life, explaining the findings of glaucoma and kidney disease in NPS patients. The variation in symptoms among people with NPS is not believed to be associated with the different mutations found in LMX1B, but may be the result of variation in the genes with which LMX1B interacts.
Other Conditions Reported In People With NPS:
There appears to be a strong association between NPS and symptoms of hypothyroidism, irritable bowel syndrome, attention deficit disorder, and thin tooth enamel. The precise nature of these associations remains unclear at this time.
Exercise is often difficult for people with Nail Patella Syndrome Muscles, tendons, and ligaments could be misaligned making certain types of exercise all but impossible. It is important to understand 'your body mechanics' and follow basic rules for stretching & exercising. Christine Brown Sargent, MEd, PT., Physical Therapy Consultant has submitted an exercise regime designed for the NPS patient (click here to view).
If you have and questions or comments concerning a medical issue,
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