SNP Shot: Genomic Insights

Nail-patella syndrome (NPS) is defined by a set of abnormalities affecting the nails, knees, elbows, and pelvis. The expression of these characteristics varies significantly from person to person, even within the same family.

Almost all individuals with NPS exhibit nail irregularities. These can include absent or underdeveloped nails, discoloration, splitting, ridges, or pitting. Fingernails tend to be more affected than toenails, with the thumbnails typically showing the most severe changes. Often, the lunulae, the crescent-shaped areas at the base of the nails, are triangular instead of their normal shape.

Skeletal abnormalities are also frequently observed in people with NPS, affecting the knees, elbows, and hips. The kneecaps (patellae) may be small, irregularly shaped, or absent altogether, and patellar dislocation is common. Some individuals may have limited arm extension or difficulty supinating (turning palms upward) with straight elbows. Additionally, the elbows may be angled outward (cubitus valgus) or display abnormal webbing. A characteristic feature of NPS is the presence of horn-like bony projections (iliac horns) on the iliac bones of the pelvis. These projections are often palpable through the skin but are asymptomatic and usually discovered during pelvic x-rays. Iliac horns are strongly associated with NPS and rarely found in individuals without the condition.

Beyond the nails and skeletal system, NPS can also impact other areas, particularly the eyes and kidneys. Individuals with NPS have an increased risk of developing early-onset glaucoma (elevated pressure within the eyes). Furthermore, some individuals may develop kidney disease, which can potentially lead to kidney failure.

Inheritance:

NPS follows an autosomal dominant inheritance pattern. This means that inheriting just one copy of the mutated gene in each cell is enough to cause the disorder. Typically, an affected individual inherits the mutation from a parent who also has NPS. However, in some instances, NPS can arise from a new, spontaneous mutation in the LMX1B gene. These cases occur in individuals with no prior family history of the condition.