bardet - biedl syndrome ( bbs ) is a rare autosomal - recessive disorder characterized by abdominal obesity , mental retardation , dysmorphic extremities , retinal dystrophy , hypogonadism , and kidney structural abnormalities or functional impairment . it is now considered a significant cause of chronic and end - stage renal disease in children . to the best of our knowledge there have been no previous studies on the role of diet in the management of renal functions in patients with bbs . two siblings , aged 32 and 27 years , with bbs are presented . on admission both patients were obese , with body mass indexes ( bmi ) of 40 and 39 kg / m . after 2 years of follow - up with a diet consisting of 0.6 g / kg / day protein and 1400 kcal / day energy , their bmi s were decreased to 29 and 27 kg / m , whereas their crcl s were increased to 44 and 32 ml / min , respectively . since this syndrome most likely results in end - stage renal disease , follow - up of renal dysfunction is essential . low protein diet and/or obesity control may slow the progression of renal failure in patients with bbs . bardet - biedl syndrome ( bbs ) is a rare autosomal - recessive disorder characterized by abdominal obesity , mental retardation , dysmorphic extremities ( syndactyly , brachydactyly or polydactyly ) , retinal dystrophy or pigmentary retinopathy , hypogonadism or hypogenitalism ( limited to male patients ) , and kidney structural abnormalities or functional impairment . beales et al . reported an increased risk of renal agenesis and renal cancer among heterozygous carriers of a bbs mutation , although this finding was not supported by a very recent study . in the last 2 decades it is now considered a significant cause of chronic and end - stage renal disease ( esrd ) in children . to the best of our knowledge there is no data about the role of diet on the management of renal functions in patients with bbs . we report 2 patients with bbs whose renal functions were improved by low protein diet and obesity control at 2-years follow - up . the first patient , a 32-year old female patient with a history of bbs , was referred to our unit for renal function impairment on june 2005 . she was born to healthy consanguineous parents and diagnosed with bbs on the basis of obesity , polydactyly ( hexadactyly of the right hand , in which a 6 digit was surgically excised ) , slight mental retardation , hypogenitalism ( hypoplastic uterus and vaginal aplasia ) and visual loss since age 5 . she was obese on admission , with a body mass index ( bmi ) of 40 kg / m , and her blood pressure was 110/70 mmhg . blood results were as follows : hgb 14 g / dl , serum creatinine 1.5 mg / dl ( ref . her creatinine clearance ( crcl ) was 41 ml / min . with a daily urinary protein excretion of 300 mg . the second patient , the 27-year old sister of the previous patient , was referred to us at the same time for renal function impairment . she also was diagnosed with bbs on the basis of polydactyly ( hexadactyly of both hands and feet , in which all extra digits were surgically excised ) , slight mental retardation , and visual loss since age 1 . at age 11 she too was obese on admission , with a bmi of 39 kg / m , and blood pressure 110/80 mmhg . blood results were as follows : hgb : 13.8 g / dl , serum creatinine 2.4 mg / dl , and blood urea nitrogen 35 mg / dl . renal ultrasound showed small , slightly hyperechoic kidneys with parenchymal cysts of a maximal diameter of 13 mm . her crcl was 24 ml / min , with a daily urinary protein excretion of 198 mg . in both patients tc - mag3 scans were performed to evaluate the severity of renal function loss . in patient 1 , tc - mag3 scan revealed slightly decreased perfusion , extraction and excretion of the radioactive tracer ( figure 1a ) . in patient 2 , tc - mag3 scans also showed poor perfusion , decreased and delayed radioactive tracer accumulation , as well as poor excretion ( more severe than that of patient 1 ) ( figure 2a ) . both patients were diagnosed with chronic kidney disease ( ckd ) based on glomerular filtration rate , and were put on a diet of daily protein intake of 0.6 g / kg and daily energy intake of 1400 kcal . compliance to the diets was very good after a period of training , and they never missed an appointment . at the end of the 2 years follow - up , on june 2007 , the bmi of the first patient decreased to 29 kg / m , and daily protein excretion decreased to 182 mg , and crcl increased to 44 ml / min . the bmi of the second patient decreased to 27 kg / m , daily protein excretion decreased to 82 mg , and crcl increased to 32 ml / min . the tc - mag3 scans were repeated to evaluate the status of renal functions . in patient 1 , the scintigraphy revealed a mild improvement in the perfusion , extraction , and excretion capability of both kidneys ( figure 1b ) . in the second patient , the control scintigraphy revealed significant improvement in the perfusion , extraction , and excretion capability of both kidneys ( figure 2b ) . here , for the first time , the improvement of renal functions by low protein diet and obesity control is reported in 2 siblings with bbs . this is also the first imaging demonstration of the clinical response to low - protein diet and obesity control therapy in 2 cases with bbs , demonstrating the potential of tc - mag3 renal scintigraphy in the follow - up of this disease . renal structural and/or functional abnormalities not only constitute one of the principal manifestations of bbs ; renal impairment is frequent and an important cause of death , which contributes to the substantially reduced survival . the renal structural and functional abnormalities in bbs include : renal parenchymal cysts , calyceal clubbing , fetal lobulation , scarring , dysplastic kidneys , unilateral agenesis , vesicoureteral reflux , hypertension , chronic renal insufficiency , end - stage renal disease , urinary concentration defects , and renal tubular acidosis . both patients presented here had atrophic kidneys with increased echogenicity , and 1 also had renal parenchymal cysts . in the 2 cases presented , intervention resulted in improvement in renal function . in patients with ckd it is known that low protein diets are associated with slower progression of renal failure , or a delay in the necessity of renal replacement therapy . low protein diet manifests its effect by ameliorating proteinuria , decreasing workload on the remaining nephrons , reducing oxidant stress , and decreasing insulin resistance . however , there is not sufficient data on the use of low protein diets in patients with bbs . at this point it may be argued that low protein diet is beneficial in patients with bbs , as it is in patients with non - bbs related ckd . several abnormalities that can lead to kidney injury have been identified in obese subjects , including insulin resistance , inappropriate activation of the renin - angiotensin - aldosterone system , as well as increased oxidative stress , coagulability , and impaired fibrinolysis . it has been demonstrated that a higher bmi is also a strong and potentially modifiable risk factor for esrd . we therefore recommend aggressive obesity control in patients with bbs as well as in non - bbs obese subjects . more clinical studies with additional patients and long - term follow - up are needed to more accurately determine the effect of obesity control on renal functions . since this syndrome most likely results in esrd , follow - up of renal dysfunction is essential . low protein diet and/or obesity control may slow the progression of renal failure in patients with bbs .
summarybackgroundbardet - biedl syndrome ( bbs ) is a rare autosomal - recessive disorder characterized by abdominal obesity , mental retardation , dysmorphic extremities , retinal dystrophy , hypogonadism , and kidney structural abnormalities or functional impairment . 
 it is now considered a significant cause of chronic and end - stage renal disease in children . to the best of our knowledge 
 there have been no previous studies on the role of diet in the management of renal functions in patients with bbs.case reportstwo siblings , aged 32 and 27 years , with bbs are presented . on admission 
 both patients were obese , with body mass indexes ( bmi ) of 40 and 39 kg / m2 . 
 their creatinine clearances ( crcl ) were 41 and 24 ml / min . 
 after 2 years of follow - up with a diet consisting of 0.6 g / kg / day protein and 1400 kcal / day energy , their bmi s were decreased to 29 and 27 kg / m2 , whereas their crcl s were increased to 44 and 32 ml / min , respectively . 
 99mtc - mag3 scintigraphy also revealed improved renal function.conclusionssince this syndrome most likely results in end - stage renal disease , follow - up of renal dysfunction is essential . 
 low protein diet and/or obesity control may slow the progression of renal failure in patients with bbs .