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].