Bardet-Biedl Syndrome – Understanding the Disease

Bardet-Biedl Syndrome (BBS) is a life-limiting orphan disease resulting from multiple gene variants that affect many organs of the body.

The Rare Disease Odyssey

BBS is part of what is known as the “rare disease odyssey”. It has been determined that on average, it takes five to seven years to come up with the right diagnosis. During this time, patients probably see anywhere between six and eight different doctors and receive an average of four different alternative diagnoses.

BBS is a Ciliopathy

BBS is part of a recently described disease category called ciliopathies that together affect up to 1 in 700 individuals spread across at least 35 diseases. Ciliopathies share a common etiology arising from dysfunction of cilia, finger-like appendages projecting from the apical surface of most cells in the body.

Cilia are ubiquitous throughout the animal kingdom and come in two broad types – motile and non-motile (primary), which are most abundant and important for cellular signaling. Primary cilia are essential components of many cell types and we are increasing our understanding of their function. Common overlapping phenotypes include defective sensory, renal, neurocognitive, and endocrine/metabolic components.

The Impact of BBS

Click the green dots for more detail.

Developmental Delay/Learning Difficulties

Speech and motor skill deficits, impaired social skills, behavioral issues, and learning difficulties are all common in patients and can persist into adulthood.

Rod Cone Dystrophy

Night vision difficulties arise by mid-childhood, followed by blind spots in the periphery of vision. Most patients are legally blind by mid-teens due to progressions in central vision loss.

Anosmia/Hyposmia

Patients can have a reduced sense of smell or inability to smell anything.

Dental Anomalies

A majority of patients experience dental anomalies due to abnormal tooth development, with thin enamel covering, dental crowding and small roots. Many also have a high-arched palate.

Endocrine Disorders

These range from an underactive thyroid to insufficient sex hormones, such as low testosterone or oestrogens.

Congenital Heart Disease

Patients are occasionally born with congenital heart anomalies (ASD, VSD) or acquire thickening of the heart’s muscular walls (LVH).

Diabetes Mellitus

From our own natural history data we see that a quarter of patients develop Type 2 diabetes mellitus at some point in their life.

Renal Anomalies

Structural renal and urinary tract anomalies, cysts and renal dysfunction affect roughly 50-80% of patients.

Genital Anomalies

Patients suffer from genital and urinary abnormalities. Males show undescended testis with small penis and infertility. Females have ovaries, uterus fallopian tubes and vagina affected.

Central Obesity

Weight gain is quickly evident in the first two years of life and becomes a life-long problem, driven by excessive eating.

Polydactyly

Patients are often born with extra fingers or toes, or digit variations such as shorter, mildly webbed or fused digits.

How Can BBS Be Diagnosed?

Prof. Beales published a set of signs and symptoms that have become the criteria for making a diagnosis of BBS. These symptoms are used to diagnose BBS in an individual before genetic testing has been completed or if the genetic testing does not reveal a mutation in a gene known to cause BBS.

BBS Communities & Additional Resources

For UK based BBS support

For U.S based BBS support

For BBS resources and clinical trials

For rare genetic obesity disorder resources and support

For rare disease resources and support