Israel Medical Association Journal

Nail-patella syndrome (NPS, OMIM: #161200), also known as Fong disease, hereditary osteo-onychodysplasia (HOOD), and Turner-Kieser syndrome, is a rare pleiotropic, multisystemic condition with an estimated incidence of 1 per 50,000. It is characterized mainly by developmental defects of dorsal limb structures due to symmetrical mesodermal and ectodermal abnormalities. It manifests as a classic clinical tetrad of distal digital abnormalities and fingernail dysplasia, which are typically bilateral and symmetrical, hypoplasia or absence of the patella, presence of iliac horns, and elbow deformities. It can also affect other structures (e.g., tendons, ligaments, and muscles), and may impact ophthalmic (glaucoma, increased ocular pressure and subsequent blindness), renal (nephropathy), neurological, orthopedic, and gastrointestinal systems. NPS can lead to sensorineural hearing loss and vasomotor problems [1,2]. Clinical manifestations vary greatly in frequency and severity. The prognosis is relatively good when clinical features are mild and cause no disability. However, serious and even life-threatening complications can occur. NPS is usually clinically diagnosed based on physical examination and radiological imaging. Genetic testing and renal biopsy can also assist in diagnosis confirmation.

Background: Children and adolescents are commonly referred to an orthopedic surgeon to assess knee malalignment.

Objectives: To assess the prevalence of genu varum and valgum among adolescents, and to identify correlates of these conditions.

Methods: A medical database of 47,588 candidates for military service presenting to the northern recruitment center during an 11 year period was analyzed to identify clinical knee alignment. Based on the standing skin surface intercondylar distance (ICD) or intermalleolar distance (IMD), the prevalence rates of genu varum (ICD ≥ 3 cm) and genu valgum (IMD ≥ 4 cm) were calculated. The association of gender, body mass index (BMI), and place of residence to knee alignment was studied.

Results: The rates of genu varum and valgum were 11.4% (5427) and 5.6% (2639), respectively. Genu varum was significantly more prevalent among males than females (16.2% vs. 4.4%, P < 0.001). It was also more prevalent among underweight subjects and less prevalent among overweight and obese subjects (P < 0.001). Genu valgum was significantly more prevalent among females than males (9.4% vs. 2.9%) and in overweight and obese subjects compared to those with normal BMI, while less prevalent in underweight subjects (P < 0.001). Multivariate analysis revealed that genu varum was independently positively associated with male gender, underweight, and living in a rural area. Genu valgum was independently positively associated with female gender, overweight, and obesity.

Conclusions: This study establishes a modern benchmark for the cutoff and prevalence of genu varum and valgum as well as associations with gender and BMI.