Bardet-Biedl Syndrome (BBS). BBS is a rare ciliopathic autosomal recessive genetic disorder with multi-system impairment primarily characterized by obesity, retinal dystrophy, polydactyly, learning difficulties, hypogonadism and renal malformations.
1 The diagnosis of BBS is based on the diagnostic criteria
2 which depends predominantly on the clinical features. For the diagnosis of this syndrome, at least four major or three major and two minor features must be found in a patient. Our patient had five primary features such as retinitis pigmentosa, polydactyly, obesity, learning disabilities, renal dysfunction and five secondary features such as speech and developmental delay, astigmatism, brachydactyly, hypodontia and high arched palate (Table 2).
As per the published reports, less than 15 cases of BBS are reported from India
1, out of which most of cases are picked up post-pubertally, which makes this case unique. Secondary features of BBS include speech delay, development delay, congenital heart disease, hepatic fibrosis, strabismus or cataract, neurological deficits, dental anomalies, diabetes mellitus and hypertension.
1,2 Apart from the secondary features, our patient had a congenital left sided complete cleft lip and palate which is not reported in any literatures associated with BBS. So far, only 3 cases of BBS has been reported to have chronic kidney disease (CKD) from India, which initially goes undetected.
3 Our case report was also similar in terms of deranged renal function tests and sonographically supported evidence of grade III chronic renal parenchymal disease with loss of cortico-medullary differentiation. Bilateral genu valgum in the child was attributed to the nutritional cause of Vitamin deficiency more than a renal cause which is chronic kidney disease (CKD) due to highly elevated alkaline phosphatase levels (>2000 IU/L). Vitamin D deficiency in this case was due to trapping of Vitamin D in the excess adipose tissue and the insufficient lipolytic stimulation causing immobilization of Vitamin D from the fat cells.
4
[Table2]
Note: For Diagnosis of Bardet Biedl syndrome, at least four major or three major and two minor features are required.
Among all the diagnostic features of BBS, the leading cause of morbidity and mortality is renal failure, where 25% die by the age of 44 years, hence such cases warrants attention.
5 These cases require a multi-disciplinary approach of management. The index case was advised to wear glasses for myopic astigmatism, speech therapy and to lose weight through proper controlled diet and exercises. Parents of the child were counselled for regular follow up to observe for response to treatment for rickets and metabolic acidosis, to watch for progressive renal changes, worsening visual disturbances, to monitor the blood pressure values, to prevent future development of diabetes mellitus and other metabolic syndrome complications. Though this patient had multiple consultations by several specialists in different facilities, the diagnosis had been missed, probably because of the rarity of this condition and by owing to the slow emergence of features like learning disabilities, retinitis pigmentosa and renal dysfunction. This index case warrants every pediatrician to track such doubtful cases on a long term basis.
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- Beales PL, Elcioglu N, Woolf AS, Parker D, Flinter FA. New criteria for improved diagnosis of Bardet-Biedl syndrome: results of a population survey. J Med Genet. 1999;36: 437-446.
- Kute VB, Vanikar AV, Gumber MR, Patel HV, Shah PR, Patil SB, et al. Bardet-biedl syndrome: a rare cause of chronic kidney disease. Indian J Clin Biochem. 2013;28:201-205.
- Migliaccio S, Di Nisio A, Mele C, Scappaticcio L, Savastano S, Colao A; Obesity Programs of nutrition, Education, Research and Assessment (OPERA) Group. Obesity and hypovitaminosis D: causality or casualty? Int J Obes Suppl. 2019;9:20-31.
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