Congenital anosmia

Title

Other Names:

Isolated congenital anosmia; ANIC

Categories:

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

Summary 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]

Last updated: 6/9/2015

Symptoms Symptoms

The Human Phenotype Ontology (HPO) provides the following list of features that have been reported in people with this condition. Much of the information in the HPO comes from Orphanet, a European rare disease database. If available, the list includes a rough estimate of how common a feature is (its frequency). Frequencies are based on a specific study and may not be representative of all studies. You can use the MedlinePlus Medical Dictionary for definitions of the terms below.

Signs and Symptoms	Approximate number of patients (when available)
Anosmia	-
Autosomal dominant inheritance	-

Last updated: 7/1/2017

Cause 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.

Last updated: 10/14/2016

Inheritance Inheritance

Most cases of isolated congenital anosmia (not associated with additional symptoms) occur sporadically in people with no family history of the condition. Rarely, more than one family member may be affected. In these families, inheritance appears to be autosomal dominant with reduced penetrance.^[1]^[3] Autosomal dominant inheritance means that having a change (mutation) in only one copy of the responsible gene in each cell is enough to cause features of the condition. Reduced penetrance means that not all people who have or inherit the mutation will be affected. When a person with a mutation that causes an autosomal dominant condition has children (whether they are affected or not), each child has a 50% (1 in 2) chance to inherit that mutation. For conditions with reduced penetrance, it is not possible to predict whether a child who inherits the mutation will be affected. In most familial cases of isolated congenital anosmia, the genetic cause is unknown.

Congenital anosmia can also by associated with hereditary genetic disorders such as Kallmann syndrome and congenital insensitivity to pain. In these cases, it is inherited in the same manner as the associated condition. For example, Kallmann syndrome can be inherited in an autosomal dominant, autosomal recessive or X-linked recessive manner depending on the underlying genetic cause (it can be caused by mutations in several different genes).^[5] Congenital insensitivity to pain has an autosomal recessive pattern of inheritance.^[6]

Last updated: 10/14/2016

Diagnosis 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

Last updated: 10/14/2016

Treatment Treatment

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

Last updated: 6/9/2015

Statistics Statistics

Studies suggest that approximately 1 in 10,000 people are affected by congenital anosmia. This includes people affected by isolated congenital anosmia (no additional symptoms) and those with congenital anosmia caused by a specific genetic disorder (such as Kallmann syndrome or congenital insensitivity to pain).^[3]

Last updated: 10/14/2016

Do you have updated information on this condition? Let us know.

Research Research

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

The Centers for Mendelian Genomics program is working to discover the causes of rare genetic disorders. For more information about applying to the research study, please visit their website.
ClinicalTrials.gov lists trials that are studying or have studied Congenital anosmia. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.
The Research Portfolio Online Reporting Tool (RePORT) provides access to reports, data, and analyses of research activities at the National Institutes of Health (NIH), including information on NIH expenditures and the results of NIH-supported research. Although these projects may not conduct studies on humans, you may want to contact the investigators to learn more. To search for studies, enter the disease name in the "Text Search" box. Then click "Submit Query".

Living With Living With

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Genetics Resources

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by GeneTests, the American College of Medical Genetics, and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.

Learn More 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.

GARD Answers GARD Answers

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

My husband was born without the sense of smell. It seems to run in his family in a hit and miss fashion. For example, his mother could not smell, his mother's sister cannot smell, two of her children cannot smell, but the 3rd one can. We have two children, a daughter who can smell, and an 8 year old son who cannot. The description of the condition seems to fit each affected person, except for the part about it affecting only one member of a family. Have you heard of a condition that is hereditary? See answer
Is there any hope for a return of smell for someone who has never smelled? I have been diagnosed by several neurologists and had the round of brain MRI with contrast and other tests. No one found a cause for my anosmia. I just wondered if there is anything that could be done to restore it after 45 years. See answer
How common is congenital anosmia? Is there a cure or any treatment?
See answer

Have a question? Contact a GARD Information Specialist.

References References

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.
Donald Leopold, MD. Disorders of Taste and Smell. Medscape Reference. April 2014; http://emedicine.medscape.com/article/861242-overview#aw2aab6b5.
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.
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.
Kallmann syndrome. Genetics Home Reference. 2008; http://ghr.nlm.nih.gov/condition/kallmann-syndrome. Accessed 12/22/2011.
Congenital insensitivity to pain. Genetics Home Reference. November 2012; http://ghr.nlm.nih.gov/condition/congenital-insensitivity-to-pain.
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.
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.