Bardet-Biedl syndrome 2 (BBS2), a variant of Bardet-Biedl syndrome (BBS), is a genetic condition that causes many different clinical symptoms. BBS is a ciliopathy disorder with several sub-types that result from different genetic mutations in at least 19 proteins, and displays a wide range of clinical features [1]. The pathogenesis of BBS stems from defective or limited functioning of cilia, due to deficiencies of the mutant proteins. This affects any organ in which cilia are found, such as the eyes and kidneys, in addition to other systems.

Features of BBS develop over time, and a few may be apparent in early childhood. Major features of the condition are retinal degeneration, obesity, polydactyly, hypogonadism and underdeveloped genitalia, intellectual impairment, and renal involvement [2]. If four of the major signs are present, then BBS can be diagnosed. It can also be diagnosed with three of the above features being present, in addition to at least two minor features [3]. The latter may include pigmentary retinopathy (retinitis pigmentosa), polycystic kidney disease, cardiovascular anomalies, aganglionic megacolon, diabetes, and hypertension [4]. Polydactyly may be the only obvious feature of BBS2 at birth.

Visual problems, in both acuity and color perception, may progress to total blindness. This is usually precipitated by retinitis pigmentosa. Affected individuals often become blind during childhood or adolescence. They may also experience delayed puberty and atresia of certain reproductive structures.

Children suffering from BBS may display behavioral abnormalities, and psychiatric illness such as autism. They may also experience developmental difficulties, exemplified by speech impairment and ataxia.

• Recurrent Urinary Tract Infection

  urinary tract infections (30% of patients) Polydactyly of hands and/or feet (major) Brachydactyly of hands Speech delays Ataxia Developmental delay Learning disabilities (major) Diabetes mellitus (15-45% of patients) A clinical diagnosis is made with [en.wikibooks.org]

• Pneumonia

  Since her birth, the child had frequent occurrences of bronchitis and pneumonia, as well as persistent auscultatory changes such as wheezing and buzz. Based on a bronchoscopic material ciliary dyskinesia was diagnosed. [omicsonline.org]

• Macrocephaly

  According to them, BBS patients display a long philtrum, thin upper lip, small mouth, brachycephaly, macrocephaly, large ears, palpebral fissures, bitemporal narrowing, and front baldness in male patients 1, 13, 16. [dentalnews.com]

• Large Ears

  According to them, BBS patients display a long philtrum, thin upper lip, small mouth, brachycephaly, macrocephaly, large ears, palpebral fissures, bitemporal narrowing, and front baldness in male patients 1, 13, 16. [dentalnews.com]

• Anger

  It is not possible to cure this condition, but regular follow-up for symptoms can improve quality of life. [ edit ] Guilt, fear, anger, anxiety, sadness, desperation, and depression are common feelings associated with this diagnosis. [en.wikibooks.org]

  Recherche Public-Santé, Luxembourg, Luxembourg Jean Muller Unité de Génétique Médicale, Université Saint Joseph Faculté de Médecine, Beirut, Lebanon Sandra Corbani, Nadine Jalkh, Nabiha Salem, Eliane Chouery & André Mégarbané Service de Génétique, CHU, Angers [nature.com]

• Psychomotor Retardation

  Clinical differential diagnoses of an obese child with psychomotor retardation and without polydactyly involve a wide range of possibilities, until visual impairment appears. 3 GENETICS OF THE BARDET-BIEDL SYNDROME There are at least 16 genes related [revistanefrologia.com]

Diagnosis of BBS is made by evaluation of the presenting symptoms, and molecular genetic testing [5]. Prenatal testing and diagnosis is possible. Genotyping may be necessary to distinguish BBS from other hereditary conditions with similar presentation.

Further tests and examinations should be conducted, as these assist physicians in gauging the extent of the illness, and thus management objectives. These procedures include:

• Ophthalmological exam
• Examination of the reproductive organs
• Determination of body mass index (BMI) and dietary needs
• Cardiovascular evaluation, including blood pressure readings and echocardiogram (ECG)
• Assessment of developmental milestones

It has been suggested in the literature that diagnosis of BBS can be made if a patient presents with at least four primary features, or a combination of three of the primary as well as two secondary features [6] [7].

1. Marion V, Schlicht D, Mockel A, et al. Bardet-Biedl syndrome highlights the major role of the primary cilium in efficient water reabsorption. Kidney Int. 2011;79(9):1013-1025.
2. Khan SA, Muhammad N, Khan MA, Kamal A, Rehman ZU, Khan S. Genetics of Human Bardet-Biedl Syndrome, an Update. Clin Genet. 2016;90(1):3-15.
3. Madireddi J, Acharya V, Suryanarayana J, Hande HM, Shetty R. Bardet-Biedl syndrome: multiple fingers with multiple defects! BMJ Case Rep. 2015; 2015: bcr2015211776.
4. M'hamdi O, Ouertani I, Chaabouni-Bouhamed H. Update on the genetics of bardet-biedl syndrome. Mol Syndromol. 2014;5(2):51–56.
5. Redin C, Le Gras S, Mhamdi O, et al. Targeted high-throughput sequencing for diagnosis of genetically heterogeneous diseases: efficient mutation detection in Bardet-Biedl and Alstrom syndromes. J Med Genet. 2012;49(8):502-512.
6. Beales PL, Katsanis N, Lewis RA, et al. Genetic and mutational analyses of a large multiethnic Bardet-Biedl cohort reveal a minor involvement of BBS6 and delineate the critical intervals of other loci. Am J Hum Genet. 2001;68:606–616.
7. 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(6):437-446.