Nail-Patella Syndrome

Signs and symptoms of NPS are usually apparent at birth or present during early childhood. Although the clinical manifestations can vary in range and severity, NPS patients typically appear very lean, with decreased muscle mass in the upper arms and legs. They usually find it challenging to gain weight, specifically muscle mass. 

Individuals with NPS usually present with abnormalities in the nails, elbows, knees, and hip bones. The most common sign is the absence or underdevelopment of fingers and toenails. Most often, the thumbnails and fifth toenails are affected. Typically, the nails are small, narrow, split, depressed, or discolored. However, they can also appear ridged, pitted, separated longitudinally, or thin. 

Patients may also have skeletal abnormalities, including the elbows and patellae. The arm bones (i.e., capitellum and radial head) that meet at the elbow may be malformed or underdeveloped, while there may also be excess skin webbing near the antecubital area. Due to these changes, the range of motion in the elbow may be limited; therefore, an affected individual might not be able to fully extend their forearm or supinate and pronate the forearm at the elbow joint. The patellae may also be malformed, underdeveloped, or completely absent. Further, like the bones that create the elbow joint, the bones in the knee joint (i.e., fibula and femur) may be malformed and underdeveloped, which can lead to subluxation of the patellae and bow-leg deformity. 

Another characteristic sign of NPS is having iliac horns, which are small horn-like outgrowths that develop on the bones of the pelvis. 

When it comes to the eyes, individuals with NPS can present with the Lester sign when there is dark pigmentation around the iris resembling a flower or clover leaf. Individuals with NPS may also develop increased pressure in their eyes, called open-angle glaucoma. If left untreated, glaucoma can lead to narrowing visual fields and significant vision loss. 

As there is no cure for NPS, treatment focuses on managing symptoms. For musculoskeletal abnormalities, treatment can include analgesics, such as nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen, if the kidneys are involved; physiotherapy; splinting; bracing; and surgery. For those with kidney disease, management may include medications (e.g., angiotensin-converting enzyme inhibitors), dialysis, and in more severe cases, renal transplantation. As for the eyes, glaucoma treatment focuses on reducing intraocular pressure and may involve using eye drops containing a combination of beta-blockers (e.g., timolol) and carbonic anhydrase inhibitors (e.g., dorzolamide, acetazolamide), or surgery (e.g., trabeculectomy). 

Due to the wide range of signs, symptoms, and presentations, individuals with NPS should be routinely monitored for new or worsening signs and symptoms. Children with the condition should be screened routinely for the development of scoliosis for early detection and treatment. All individuals should follow closely with an ophthalmologist to monitor for glaucoma, cataracts, or a visual impairment, in addition to close monitoring of kidney function for nephropathy.