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Congenital deafness with labyrinthine aplasia, microtia, and microdontia (also called LAMM syndrome) is a condition that affects development of the ears and teeth. In people with this condition, the structures that form the inner ear are usually completely absent (labyrinthine aplasia). Rarely, affected individuals have some underdeveloped inner ear structures in one or both ears. The abnormalities of the inner ear cause a form of hearing loss called sensorineural deafness that is present from birth (congenital). Because the inner ear is important for balance as well as hearing, development of motor skills, such as sitting and crawling, may be delayed in affected infants. In addition, people with LAMM syndrome often have abnormally small outer ears (microtia) with narrow ear canals. They can also have unusually small, widely spaced teeth (microdontia).
LAMM syndrome is a rare condition, although its prevalence is unknown. Approximately a dozen affected families have been identified.
LAMM syndrome is caused by mutations in the FGF3 gene, which provides instructions for making a protein called fibroblast growth factor 3 (FGF3). By attaching to another protein known as a receptor, the FGF3 protein triggers a cascade of chemical reactions inside the cell that signal the cell to undergo certain changes, such as dividing or maturing to take on specialized functions. During development before birth, the signals triggered by the FGF3 protein stimulate cells to form the structures that make up the inner ears. The FGF3 protein is also involved in the development of many other organs and structures, including the outer ears and teeth.
FGF3 gene mutations involved in LAMM syndrome alter the FGF3 protein. The altered protein likely has reduced or absent function and is unable to stimulate signaling. The loss of FGF3 function impairs development of the ears and teeth, which leads to the characteristic features of LAMM syndrome.
Changes in this gene are associated with congenital deafness with labyrinthine aplasia, microtia, and microdontia.
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
These resources address the diagnosis or management of LAMM syndrome and may include treatment providers.
You might also find information on the diagnosis or management of LAMM syndrome in Educational resources (http://www.ghr.nlm.nih.gov/condition/congenital-deafness-with-labyrinthine-aplasia-microtia-and-microdontia/show/Educational+resources) and Patient support (http://www.ghr.nlm.nih.gov/condition/congenital-deafness-with-labyrinthine-aplasia-microtia-and-microdontia/show/Patient+support).
General information about the diagnosis (http://ghr.nlm.nih.gov/handbook/consult/diagnosis) and management (http://ghr.nlm.nih.gov/handbook/consult/treatment) of genetic conditions is available in the Handbook. Read more about genetic testing (http://ghr.nlm.nih.gov/handbook/testing), particularly the difference between clinical tests and research tests (http://ghr.nlm.nih.gov/handbook/testing/researchtesting).
To locate a healthcare provider, see How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.
You may find the following resources about LAMM syndrome helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines (http://ghr.nlm.nih.gov/ConditionNameGuide) and How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
Ask the Genetic and Rare Diseases Information Center (http://rarediseases.info.nih.gov/GARD/).
agenesis ; autosomal ; autosomal recessive ; cell ; congenital ; fibroblast ; gene ; growth factor ; motor ; prevalence ; protein ; receptor ; recessive ; sensorineural ; syndrome
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.