Laurence-Moon-Bardet-Biedl syndrome

Laurence-Moon-Bardet-Biedl Syndrome

Laurence-Moon-Bardet-Biedl syndrome (LMBBS) is a rare genetic disorder that affects multiple body systems. It is characterized by a combination of symptoms that can include retinal degeneration, obesity, polydactyly, hypogonadism, renal abnormalities, and intellectual disability. LMBBS is considered a ciliopathy, as it involves dysfunction of the cilia, which are hair-like structures on the surface of cells that play a crucial role in cell signaling and function.

History

The syndrome was first described in 1866 by John Zachariah Laurence and Robert Charles Moon, who noted the association of retinal degeneration and obesity. Later, in the 1920s, Georges Bardet and Arthur Biedl independently described additional features of the syndrome, including polydactyly and hypogonadism. The condition was initially thought to be two separate syndromes, Laurence-Moon syndrome and Bardet-Biedl syndrome, but it is now recognized as a single entity with variable expression.

Genetics

LMBBS is inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to be affected. Several genes have been associated with LMBBS, including BBS1, BBS2, BBS4, and others. These genes are involved in the function of cilia, and mutations lead to the diverse symptoms seen in the syndrome.

Clinical Features

The clinical presentation of LMBBS can vary widely among affected individuals, but common features include:

• Retinal degeneration: Progressive loss of vision due to retinitis pigmentosa, often leading to blindness.
• Obesity: Typically begins in childhood and can be severe.
• Polydactyly: Extra fingers or toes, which may be present at birth.
• Hypogonadism: Underdeveloped genitalia and delayed or absent puberty.
• Renal abnormalities: Structural kidney defects or functional impairment, which can lead to kidney failure.
• Intellectual disability: Ranges from mild to moderate.

Diagnosis

Diagnosis of LMBBS is based on clinical evaluation and the presence of characteristic features. Genetic testing can confirm the diagnosis by identifying mutations in one of the associated genes. Early diagnosis is important for managing symptoms and preventing complications.

Management

There is no cure for LMBBS, and treatment is symptomatic and supportive. Management may include:

• Regular monitoring and treatment of vision problems.
• Weight management through diet and exercise.
• Surgical correction of polydactyly if necessary.
• Hormone replacement therapy for hypogonadism.
• Monitoring and treatment of renal function.
• Educational support for intellectual disability.

Prognosis

The prognosis for individuals with LMBBS varies depending on the severity of symptoms and the presence of complications. Early intervention and comprehensive management can improve quality of life.

Also see

• Retinitis pigmentosa
• Ciliopathy
• Autosomal recessive disorder
• Polydactyly