Nail-patella syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Nail-patella syndrome is characterized by abnormalities of the nails, knees, elbows, and pelvis. The features of nail-patella syndrome vary in severity between affected individuals, even among members of the same family.

Nail abnormalities are seen in almost all individuals with nail-patella syndrome. The nails may be absent or underdeveloped and discolored, split, ridged, or pitted. The fingernails are more likely to be affected than the toenails, and the thumbnails are usually the most severely affected. In many people with this condition, the areas at the base of the nails (lunulae) are triangular instead of the usual crescent shape.

Individuals with nail-patella syndrome also commonly have skeletal abnormalities involving the knees, elbows, and hips. The kneecaps (patellae) are small, irregularly shaped, or absent, and dislocation of the patella is common. Some people with this condition may not be able to fully extend their arms or turn their palms up while keeping their elbows straight. The elbows may also be angled outward (cubitus valgus) or have abnormal webbing. Many individuals with nail-patella syndrome have horn-like outgrowths of the iliac bones of the pelvis (iliac horns). These abnormal projections may be felt through the skin, but they do not cause any symptoms and are usually detected on a pelvic x-ray. Iliac horns are very common in people with nail-patella syndrome and are rarely, if ever, seen in people without this condition.

Other areas of the body may also be affected in nail-patella syndrome, particularly the eyes and kidneys. Individuals with this condition are at risk of developing increased pressure within the eyes (glaucoma) at an early age. Some people develop kidney disease, which can progress to kidney failure.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the LMX1B gene cause nail-patella syndrome. The LMX1B gene provides instructions for producing a protein that attaches (binds) to specific regions of DNA and regulates the activity of other genes. On the basis of this role, the LMX1B protein is called a transcription factor. The LMX1B protein appears to be particularly important during early embryonic development of the limbs, kidneys, and eyes. Mutations in the LMX1B gene lead to the production of an abnormally short, nonfunctional protein or affect the protein's ability to bind to DNA. It is unclear how mutations in the LMX1B gene lead to the signs and symptoms of nail-patella syndrome.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Nail-patella syndrome is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person inherits the mutation from one affected parent. Other cases may result from new mutations in the LMX1B gene. These cases occur in people with no history of the disorder in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

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

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormal digit morphology · Very frequent (99-80%)

A morphological abnormality of a digit, i.e., of a finger or toe.

Abnormal nail morphology · Very frequent (99-80%)

Abnormal structure or appearance of the nail.

Abnormal iris pigmentation · Frequent (79-30%)

Abnormal pigmentation of the iris.

Abnormality of the elbow · Frequent (79-30%)

An anomaly of the joint that connects the upper and the lower arm.

Abnormality of the kidney · Frequent (79-30%)

An abnormality of the kidney.

Abnormality of the knee · Frequent (79-30%)

An abnormality of the knee joint or surrounding structures.

Arthritis · Frequent (79-30%)

Inflammation of a joint.

Back pain · Frequent (79-30%)

An unpleasant sensation characterized by physical discomfort (such as pricking, throbbing, or aching) localized to the back.

Other findings in the same source

From: Orphanet

Additional reported features include Constipation (Frequent (79-30%)); Elbow flexion contracture (Frequent (79-30%)); Fingernail dysplasia (Frequent (79-30%)); Flexion contracture (Frequent (79-30%)); Iliac horns (Frequent (79-30%)); Morphological abnormality of the gastrointestinal tract (Frequent (79-30%)); Pes planus (Frequent (79-30%)); Decreased muscle mass (Frequent (79-30%)); Equinovarus deformity (Frequent (79-30%)); Abnormal cranial nerve physiology (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Nail-patella syndrome is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Nail-patella syndrome. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.