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Disease Profile

Congenital anosmia

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.
<1 / 1 000 000

< 331

US Estimated

< 514

Europe Estimated

Age of onset

Infancy

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ICD-10

Q07.8

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

Isolated congenital anosmia; ANIC

Categories

Congenital and Genetic Diseases; Ear, Nose, and Throat Diseases

Summary

Congenital anosmia is a condition in which people are born with a lifelong inability to smell. It may occur as an isolated abnormality (no additional symptoms) or be associated with a specific genetic disorder (such as Kallmann syndrome or congenital insensitivity to pain). Isolated congenital anosmia is usually sporadic, although some familial cases have been reported. In most cases of isolated congenital anosmia, the genetic cause in unknown.[1] Unfortunately, there is currently no cure or treatment for congenital anosmia.[2]

Symptoms

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
Percent of people who have these symptoms is not available through HPO
Anosmia
Lost smell
0000458
Autosomal dominant inheritance
0000006

Cause

Congenital anosmia may occur as an isolated abnormality or be associated with specific genetic disorders (such as Kallmann syndrome and congenital insensitivity to pain).[1]

Most cases of isolated congenital anosmia (not associated with additional symptoms) occur sporadically in people with no family history of the condition. In these people, the exact underlying cause of the condition is unknown. Scientists suspect that the condition is due to abnormal development of the olfactory system (the sensory system used for sense of smell) prior to birth. This may include abnormalities of the nasal cavity; disruptions in the pathway that carries information from the nose to the brain; or malformations of the portion of the brain that processes sense of smell.[1]

When isolated congenital anosmia affects more than one family member, it may have a genetic component. One study found that some people affected by isolated congenital anosmia have changes (mutations) in the PROKR2 gene or PROK2 gene. These genes have previously been reported in people with Kallmann syndrome (an inherited condition associated with congenital anosmia and other symptoms).[1][3] Another study found that two brothers with anosmia had a mutation in the CNGA2 gene.[4] However, in most familial cases of isolated congenital anosmia, the cause remains unknown.

Diagnosis

Isolated congenital anosmia (not associated with other symptoms) is a diagnosis of exclusion. This means that the diagnosis is made by ruling out all known conditions that may cause an absent sense of smell. When an affected person has no recollection of ever being able to smell, the following tests may be ordered to support a diagnosis of congenital anosmia:[2][7][8]

  • A thorough physical examination and medical history to look for other conditions that may interfere with sense of smell
  • Smell tests, particularly those that determine the smallest amount of odor that someone can detect
  • Brain Imaging (such as CT scan and MRI scan) to look for malformations in the portion of the brain that processes smell
  • Nasal endoscopy to look for abnormalities of the nasal cavity which may interfere with sense of smell
  • Olfactory nerve testing to evaluate disruptions in the pathway that carries information from the nose to the brain

Treatment

Unfortunately, there is currently no known cure or treatment for congenital anosmia.[2]

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.

In-Depth Information

  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Congenital anosmia. Click on the link to view a sample search on this topic.

References

  1. Karstensen HG, Tommerup N. Isolated and syndromic forms of congenital anosmia. Clin Genet. March 2012; 81(3):210-215. https://www.ncbi.nlm.nih.gov/pubmed/21895637.
  2. Donald Leopold, MD. Disorders of Taste and Smell. Medscape Reference. April 2014; https://emedicine.medscape.com/article/861242-overview#aw2aab6b5.
  3. Moya-Plana A, Villanueva C, Laccourreye O, Bonfils P, de Roux N. PROKR2 and PROK2 mutations cause isolated congenital anosmia without gonadotropic deficiency. Eur J Endocrinol. December 2012; 168(1):31-37. https://www.ncbi.nlm.nih.gov/pubmed/23082007.
  4. Karstensen HG, Mang Y, Fark T, Hummel T, Tommerup N. The first mutation in CNGA2 in two brothers with anosmia. Clin Genet. September, 2015; 88(3):293-296. https://www.ncbi.nlm.nih.gov/pubmed/25156905.
  5. Kallmann syndrome. Genetics Home Reference. 2008; https://ghr.nlm.nih.gov/condition/kallmann-syndrome. Accessed 12/22/2011.
  6. Congenital insensitivity to pain. Genetics Home Reference. November 2012; https://ghr.nlm.nih.gov/condition/congenital-insensitivity-to-pain.
  7. Frasnelli J, Fark T, Lehmann J, Gerber J, Hummel T. Brain structure is changed in congenital anosmia. Neuroimage. December 2013; 83:1074-1080. https://www.ncbi.nlm.nih.gov/pubmed/23927902.
  8. Vowles RH, Bleach NR, Rowe-Jones JM. Congenital anosmia. Int J Pediatr Otorhinolaryngol. August 1997; 41(2):207-214. https://www.ncbi.nlm.nih.gov/pubmed/9306177.

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