Bilateral renal stones associated with nail-patella syndrome

Arthropathy and proteinuria: nail-patella syndrome revisited

Nail-patella syndrome (NPS) is a pleiotropic autosomal-dominant disorder due to mutations in the gene LMX1B. It has traditionally been characterized by a tetrad of dermatologic and musculoskeletal abnormalities. However, one of the most serious manifestations of NPS is kidney disease, which may be present in up to 40% of affected individuals. Although diagnosis can be made at birth, it is often missed, presumably due to the rarity of the condition.

A 35-year-old female presented to our clinic with history of small joint pain of 6 months duration. In addition she complained of pedal edema off and on for the last 12 years. Prior to her current presentation she had been managed by a local doctor symptomatically. On evaluation, a nephrotic syndrome was obvious, but no secondary cause could be found. However, her physical examination was characteristic of NPS and keeping in view the autosomal dominant nature of the disorder all her three siblings were screened who too showed classical features of NPS. This rare syndrome as a cause of nephrotic range proteinuria is discussed in this report. The report underlines the importance of a good physical examination in a given clinical setting.

Kidney disease in nail-patella syndrome

Nail-patella syndrome (NPS) is a pleiotropic autosomal-dominant disorder due to mutations in the gene LMX1B. It has traditionally been characterized by a tetrad of dermatologic and musculoskeletal abnormalities. However, one of the most serious manifestations of NPS is kidney disease, which may be present in up to 40% of affected individuals. Although LMX1B is a developmental LIM-homeodomain transcription factor, it is expressed in post-natal life in the glomerular podocyte, suggesting a regulatory role in that cell. Kidney disease in NPS seems to occur more often in some families with NPS, but it does not segregate with any particular mutation type or location. Two patterns of NPS nephropathy may be distinguished. Most affected individuals manifest only an accelerated age-related loss of filtration function in comparison with unaffected individuals. Development of symptomatic kidney failure is rare in this group, and proteinuria (present in approximately one-third) does not appear to be progressive. A small minority (5-10%) of individuals with NPS develop nephrotic-range proteinuria as early as childhood or young adulthood and progress to end-stage kidney failure over variable periods of time. It is proposed that this latter group reflects the effects of more global podocyte dysfunction, possibly due to the combination of a mutation in LMX1B along with an otherwise innocuous polymorphism or mutation involving any of several genes expressed in podocytes (e.g. NPHS2, CD2AP), the transription of which is regulated by LMX1B.