Laurence-Moon syndrome
Encyclopedia
Laurence–Moon syndrome is a rare autosomal
recessive genetic disorder
associated with retinitis pigmentosa
, spastic paraplegia
, hypogonadism
and mental retardation
.
LMS is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome
, and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry
one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.
and Robert Charles Moon
who provided the first formal description of the condition in a paper published in 1866.
In the past, LMS has also been referred to as Laurence–Moon–Bardet–Biedl or Laurence–Moon–Biedl–Bardet syndrome, but Bardet–Biedl syndrome (BBS) is now usually recognized as a separate entity.
Recent advances in genetic typing
of the phenotypically
-wide variation in patients clinically diagnosed with either Bardet-Biedl Syndrome (BBS) or Laurence-Moon Syndrome (LMS) have questioned whether LMS and BBS are genetically distinct. For example, a 1999 epidemiological study of BBS and LMS reported that "BBS proteins interact and are necessary for the development of many organs." "Two patients [in the study] were diagnosed clinically as LMS but both had mutations in a BBS gene. The features in this population do not support the notion that BBS and LMS are distinct."
A more recent 2005 paper also suggests that the two conditions are not distinct.
Autosome
An autosome is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females. For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X and Y...
recessive genetic disorder
Genetic disorder
A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....
associated with retinitis pigmentosa
Retinitis pigmentosa
Retinitis pigmentosa is a group of genetic eye conditions that leads to incurable blindness. In the progression of symptoms for RP, night blindness generally precedes tunnel vision by years or even decades. Many people with RP do not become legally blind until their 40s or 50s and retain some...
, spastic paraplegia
Spasticity
Spasticity is a feature of altered skeletal muscle performance in muscle tone involving hypertonia, which is also referred to as an unusual "tightness" of muscles...
, hypogonadism
Hypogonadism
Hypogonadism is a medical term for decreased functional activity of the gonads. Low testosterone is caused by a decline or deficiency in gonadal production of testosterone in males...
and mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
.
Genetics
LMS is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome
Autosome
An autosome is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females. For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X and Y...
, and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry
Genetic carrier
A genetic carrier , is a person or other organism that has inherited a genetic trait or mutation, but who does not display that trait or show symptoms of the disease. They are, however, able to pass the gene onto their offspring, who may then express the gene...
one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.
Eponym and nomenclature
It is named after the physicians John Zachariah LaurenceJohn Zachariah Laurence
John Zachariah Laurence was an English ophthalmologist who practiced medicine in London. He was the founder of the South London Ophthalmic Hospital in 1857, which later became known as the Royal Eye Clinic....
and Robert Charles Moon
Robert Charles Moon
Robert Charles Moon was an ophthalmologist who practiced medicine in England and the United States. He was son of William Moon , inventor of Moon type, an embossed alphabet for the blind....
who provided the first formal description of the condition in a paper published in 1866.
In the past, LMS has also been referred to as Laurence–Moon–Bardet–Biedl or Laurence–Moon–Biedl–Bardet syndrome, but Bardet–Biedl syndrome (BBS) is now usually recognized as a separate entity.
Recent advances in genetic typing
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...
of the phenotypically
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
-wide variation in patients clinically diagnosed with either Bardet-Biedl Syndrome (BBS) or Laurence-Moon Syndrome (LMS) have questioned whether LMS and BBS are genetically distinct. For example, a 1999 epidemiological study of BBS and LMS reported that "BBS proteins interact and are necessary for the development of many organs." "Two patients [in the study] were diagnosed clinically as LMS but both had mutations in a BBS gene. The features in this population do not support the notion that BBS and LMS are distinct."
A more recent 2005 paper also suggests that the two conditions are not distinct.