Discussion
Clinical diagnosis of BBS is based on a set of modified diagnostic criteria established by Beales J. et al . According to these criteria, either four primary features or three primary and two secondary features are required to diagnose the disease[4]. Retinitis pigmentosa, polydactyly and obesity appear to be the hallmark clinical presentation[5].
Symptoms characterized as primary and secondary features are shown inTable 1 . The initial clinical presentation occurs in the first decade of life with polydactyly present at birth. The age of diagnosis varies and depends on the age at which the onset of symptomatic rod-cone dystrophy occurs. This presents as night blindness, photophobia and loss of color vision. Most patients become legally blind by the third decade of life. Electroretinography is the gold standard investigation, and may show early changes in the first two years of life. Obesity is one of the most common findings that is reported. The incidence of truncal obesity in BBS patients is reported to be 72-86% [6].
Renal and urinary tract anomalies and renal dysfunction; causes of considerable morbidity, are reported to affect 53%–82% of patients with BBS [7]. Hypertension may occur in 50%-60% of cases [8]. Renal disease can also be secondary to hypertension and diabetes; two conditions frequently seen in this population. A study carried out in 2017 suggests that patients with BBS either develop chronic kidney disease in childhood or remain entirely free of it. The proportion that does develop adult onset renal disease may also have comorbidities associated to BBS such as hypertension and diabetes. Thirty-five percent of patients were hypertensive and the most commonly prescribed antihypertensives were angiotensin converting enzyme (ACE) inhibitors [9].
At present, patients with BBS can only be treated symptomatically. The primary focus is on the management of diabetes, hypertension and metabolic syndrome in order to reduce their effect on already affected organs such as the eyes and kidneys. Weight management is a constant struggle for most patients. Many opt to have bariatric surgery or use anti-obesity medications but the safest and most effective weight loss strategy is dietary restriction [10]. As it stands, there is no definitive treatment to prevent deterioration of vision. Early evaluation by a specialist can help limit disability by providing patients with vision aids and mobility training[11]. Surgical intervention is indicated for some of the associated physical conditions, including polydactyly, some genitourinary abnormalities and congenital heart defects. In the setting of severe kidney failure later in life, kidney transplantation may be advised.
Blood pressure should be measured six monthly or more often in the setting of hypertension. Treatment of hypertension in BBS is no different from that of essential hypertension. Lifestyle modifications should be implemented to prevent hypertension. Antihypertensives and lipid-lowering medication should be prescribed as appropriate. In children and adolescents, pharmacologic treatment should be started with ACE inhibitors, angiotensin receptor blockers, long acting calcium channel blockers or thiazide diuretics [5] [12].