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Congenital Anosmia

What is Congenital Anosmia?

Congenital anosmia is a rare condition characterized by a complete lack of the ability to smell from birth. Congenital means “from birth” and anosmia is formed from the antithesis of the Greek word osme meaning “to smell.” Many may experience a form of anosmia during their lifetime, as it can occur temporarily due to congestion obstructing the nasal passage or the result of an accident severing an olfactory nerve (the olfactory bulb is the portion of the brain that receives signals from the nasal cavity and relays them to the brain as a “smell”). However, congenital anosmia is much less common, occurring in only about 1 in 10,000 people. Patients diagnosed with congenital anosmia have no concept of what a smell is, and often don’t discover they have this abnormality until informed by someone else. School-aged children with the rare disease discover it when their peers identify distinctive odors and they cannot share in the sensation. The lack of a sense of smell from birth can be related to other rare genetic disorders such as Kallmann syndrome (abnormalities in cognition that affect the senses) and congenital insensitivity to pain or may be an isolated finding with no other abnormalities.

 

Synonyms

  • Kallmann Syndrome
  • Congenital hypogonadotropic hypogonadism

Congenital anosmia is a rare condition characterized by a complete lack of the ability to smell from birth. Congenital means “from birth” and anosmia is formed from the antithesis of the Greek word osme meaning “to smell.” Many may experience a form of anosmia during their lifetime, as it can occur temporarily due to congestion obstructing the nasal passage or the result of an accident severing an olfactory nerve (the olfactory bulb is the portion of the brain that receives signals from the nasal cavity and relays them to the brain as a “smell”). However, congenital anosmia is much less common, occurring in only about 1 in 10,000 people. Patients diagnosed with congenital anosmia have no concept of what a smell is, and often don’t discover they have this abnormality until informed by someone else. School-aged children with the rare disease discover it when their peers identify distinctive odors and they cannot share in the sensation. The lack of a sense of smell from birth can be related to other rare genetic disorders such as Kallmann syndrome (abnormalities in cognition that affect the senses) and congenital insensitivity to pain or may be an isolated finding with no other abnormalities.

Acknowledgement of Congenital Anosmia has not been added yet.

Congenital anosmia and other closely related genetic disorders affecting the sense of smell are estimated to occur in 1 in 10,000 people. Only 15 people have been described as having congenital anosmia unrelated to Kallmann syndrome or other rare genetic disorders (Kallmann syndrome affects 1 in 10,000 men and 1 in 50,000 women).

Name Abbreviation
Kallmann Syndrome
Congenital hypogonadotropic hypogonadism

An individual living with congenital anosmia can experience loss of smell as either an isolated incident or as the symptom of another rare disorder. Isolated congenital anosmia (ICA) refers to the lack of only one’s sense of smell from birth. Isolated anosmia is not associated with other abnormalities, nor is the exact genetic cause known. It is thought to be related to defects during the development of the olfactory bulbs in the brain (neural structure involved in producing a sense of smell) prior to birth, or the replacement of the cells specialized in detecting smells in the nasal cavity in the airway. The human sense of smell is actually a process of recognizing compounds with an odor and signaling the brain to detect a scent. The odor compounds enter the nostril(s) of the nose, are absorbed into the skin (epithelium) layer in the nasal passage, recognize and bind to specific proteins on the surface of olfactory cells called olfactory receptors, and the olfactory receptor produces an electrochemical signal that passes to the brain via neuron cell signaling. ICA can be caused by disrupted activity or development in three levels of smell signal transduction from the nose to the brain:

  1. Defects in the transportation of odors to the cells in the nasal cavity that detect the presence of odorous molecules and send nervous signals to the brain (olfactory neuroepithelium) caused by congenital malformations in the nasal cavity that obstruct the nose

  2. Disruption of signal transduction or propagation in olfactory cells that carry the nervous signal from the nasal cavity to the brain

  3. Malformation of olfactory regions of the brain

Congenital anosmia may also be associated with other abnormalities in development or senses. While the exact genetic mutation causing congenital anosmia is unknown, studies have indicated that CNGA2 gene mutations may lead to the reported symptoms. These genetic mutations may also play a role in the development of other rare diseases that cause congenital anosmia as one of the symptoms. A case study involving twin boys with diagnosed congenital anosmia determined that they each had a shortened, damaged copy of CNGA2 on the X-chromosome. A shortened gene lacks important information to form a protein, leading to a non-functional protein product. The CNGA2 gene encodes a part of an olfactory channel located in olfactory sensory neuron cells that is responsible for responding to odors and transmitting messages to the brain to perceive “smell”. There is some evidence that the genes GNA1, ADCY3, and CNGA2 may be involved in detecting smell and that mutations may cause anosmia. Several syndromes in which congenital anosmia presents as one of the traits include Kallmann syndrome, congenital insensitivity to pain, CHARGE syndrome, Bardet -Biedl syndrome, Leber congenital amaurosis, Refsum disease and additional syndromes.

 

An individual affected by congenital anosmia will have no ability to smell odors. This lack of a sense of smell is present from birth, and often the individual will be unaware of odors. Due to lack of smell, individuals with anosmia have reported that their sense of taste is also diminished or affected. Food may be distinguished by general qualities such as texture and strong flavors, but lack subtle differences such as the difference in sweetness between fruit and chocolate. This can cause individuals to lose interest in food. 

 

Name Description
Lack of smell Present from birth, an individual with anosmia will lack the ability to smell
Lack of taste Due to lack of smell, an individual with anosmia have an altered or no ability to taste

A diagnosis of congenital anosmia involves ruling out all other known conditions that cause lack of smell (injury, lack of development of nasal cavities, blockage, etc.). For example, hyposmia is the loss of a sense of smell during one’s lifetime, usually due to accidents, injury, or in the temporary case congestion. Typically, a person with congenital anosmia will have no known recollection of smell. This will result in administration of different tests to determine the level of affliction and the possibility of other related inherited disabilities.

 

In order to determine that a person experiencing anosmia has isolated congenital anosmia, a doctor may prescribe one or several tests. These diagnostic tests are designed to evaluate the individual’s sense of smell and whether other factors are contributing to its loss. To test an individual for ability (if any) to smell:

  1. Smell tests (Sniffin’ Sticks or UPSIT test): The University of Pennsylvania developed a smell identification test to determine the smallest amount of odor that a person is capable of detecting. The individual is instructed to “scratch and sniff” a number of surfaces with varying odors and concentrations and then select from a list of multiple options matching the odor description and/or source.

  2. Odorant confusion matrix: An individual is exposed to 10 random smells a total of 10 times, and instructed to identify the odor. Anyone scoring less than 10% of correct answers is believed to have total anosmia

  3. Threshold testing: Designed to test the degree of anosmia that someone experiences, this test exposes a person to two sprays: one with an odorant (often rubbing alcohol) and one with only water. They must identify which spray contains the odorant. With each round, the concentration of odorant in water will be decreased to determine the minimum amount necessary for the individual to effectively smell. 

To test an individual for abnormalities in the olfactory region (area of the brain that receives signals from the nose and translates them to smell) or other areas of the nasal passage:

  1. CT scan: A CT scan of the brain may or may not involve the use of a contrast agent (a harmless chemical injected through IV designed to allow better visualization of an organ in the body). The individual’s brain is examined using x-rays to determine whether their olfactory region has abnormalities or lack of development.

  2. Nasal endoscopy: A small tube and camera is inserted through the nostril into the nasal passage to evaluate it for abnormalities.

  3. Olfactory nerve test: While the olfactory bulb may have developed normally, disruptions in the neural pathways to the proper processing centers in the brain would result in the inability to discern smells. This test can be conducted by exposing an individual to a smell while blindfolded (inhibiting other senses) or while keeping their nose pinched (testing changes caused by blockage).

There is currently no treatment available to individuals with isolated congenital anosmia. The primary method to cope with this lack of sense is to find ways to interact with one’s surroundings without relying on smell. Individuals that have been born without a sense of smell or lose it during their lifetime attempt to enjoy food in other ways, such as overseasoning or focusing on the sensation or “mouth-feel” when eating. 

 

While individuals with isolated congenital anosmia may not have symptoms of discomfort or other related health problems, they may lack the ability to discern certain situations involving smell. This may present dangers that go unnoticed such as a gas burner left on the stove, smoke from a nearby fire, spoiled or rotten food, and other signals meant to stimulate the brain and warn the person. A patient should be mindful of this lack of smell and rely on other senses and the help of others. In addition, patients with an affected sense of taste as a result of anosmia should seek other ways to enjoy food and eating. If the congenital anosmia is associated with another underlying syndrome, the prognosis would vary and may affect the quality of life or lifespan due to factors contributed by the underlying condition.

 

Individuals with anosmia may find it helpful to seek enjoyment in food in new and different ways. The website Anosmic Chef contains recipes written by a person with anosmia for others living without a lack of smell or taste https://anosmicchef.wordpress.com/

  1. https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Expert=88620&lng=EN

  2. https://rarediseases.info.nih.gov/diseases/9486/congenital-anosmia#:~:text=In%20most%20familial%20cases%20of%20isolated%20congenital%20anosmia%2C%20the%20genetic,manner%20as%20the%20associated%20condition.

  3. https://www.fifthsense.org.uk/congenital-anosmia/

  4. https://www.nature.com/articles/s41598-017-02947-y

  5. Alkelai, A. et al. Next-generation sequencing of patients with congenital anosmia. Eur. J. Hum. Genet. 25, (2017).

  6. Karstensen, H. G. & Tommerup, N. Isolated and syndromic forms of congenital anosmia. Clinical Genetics vol. 81 (2012).

  7. Karstensen, H. G., Mang, Y., Fark, T., Hummel, T. & Tommerup, N. The first mutation in CNGA2 in two brothers with anosmia. Clin Genet 88, 293–6 (2015).

  8. Vowles, R. H., Bleach, N. R. & Rowe-Jones, J. M. Case report: Congenital anosmia. Int. J. Pediatr. Otorhinolaryngol. 41, (1997).

Anosmia.net - What happened? Created by RSLancastr
Last updated 27 Nov 2011, 03:25 PM

Posted by RSLancastr
27 Nov 2011, 03:25 PM

At one time, I was a moderator for anosmia.net, known as The Congenital Anosmia Forum. Then, on August 4, 2008, I was hospitalized (see my thread "My Stroke" for details). Once I was discharged back home (June 30 2009), I tried to log into anosmia.net, only to find that it no longer existed! Unfortunately, my PC suffered a hard drive crash while I was in hospital, so I lost all of the contact info I had for my friends at Anosmia.net. :( Does anyone here have any contact with anyone from the old Anosmia.net? If so, please contact me with them at RSLancastr@aol.com. Sadly, all I remember of the people from there is this: The owner and administrator of the site was a woman named Steph, who lived (I believe) in Hawaii. The other moderators on the site were: 1. Polarbear - he was fond of (what he referred to as "wielding the Banhammer - banning any miscreants (such as Spammers) from the site. His avatar was a graphic of a polar bear using an innertube as a sled. 2. Breanne18 - A woman I corresponded with a fair amount.. Her avatar was a female D&D-type character holding a sword. Any info anyone may have on the site, or these people, would be greatly appreciated. Thanks, RSL

My Stroke Created by RSLancastr
Last updated 26 Nov 2011, 05:12 AM

Posted by RSLancastr
26 Nov 2011, 05:12 AM

Please forgive the typos in that last post. I'll blame them on the stroke, only because it's a convenient excuse.

Posted by RSLancastr
26 Nov 2011, 05:09 AM

During my extended hospital stay following the stroke, I occasionally wondered if the damage the stroke had done to my brain might somehow effect my anosmia. Would I develop a sense of smell, even if only partially, perhaps only via one nostril? Would my anosmia be even more pronounced on the left side of my body? (how more prounced that "non-existant could it possibly be? The answer, in my case anyway, was that the stroke has caused no discernible difference in my anosmia one way or the other. But had my stroke imapted another area of my brain (the area dealing with sense of smell), who knows what might have happened?

Posted by RSLancastr
26 Nov 2011, 04:59 AM

On August 4, 2008, I suffered a MASSIVE stroke. It put me in a coma-like state for two months, and in various hospitals, physical rehab centers and such for a total of eleven months, and made me a "left-side hemiplegic" (I have very little control over the left half of my body), and I've lived my life in a motorized wheelchair ever since. Fortunately for me, I have The Bestest Wife In The World, My Susan. She possibly saved my life, and at minimum saved me from further brain damage by immediately calling 911, despite my objections ("Don' call 911. Ahm prfckly fahn...") She was my tireless healthcare advocate for those eleven months I was in hospitals and such, and has been my tireless (okay, she tires now and then) caregiver ever since. I'm not a religious man, but if I were in charge of the dictionary, The word "blessing" would have a picture of My Susan next to it. I mention my stroke here because I think it was caused, indirectly, by my Anosmia. As a child, I learned that food tasted better to me if I salted it. I ended up salting the bejeebers out of EVERYTHING I ate - compensating, I think, for my anosmia's blunting the flavor of food. Over thedecades, this sodium intake resulted in an insanely high blood pressure (300/180 at one point). I also think that anosmics tend to attach far more importance to food's texture than other people do, perhaps compensating for the missing "aroma" piece of the Flavor Equation. For me, the preferred texture was CRUNCHY. This translated to a love of fried foods, which, along with my huge sodium intake, made me pack on the pounds. At the time of my stroke, I weighed 398 pounds. For a 6'1" tall man, that put me beyond Morbidly Obese. So, a morbidly obese 50-year-old man with insanely high blood pressure made me a stroke or heart attack just waiting to happen. So yes, I believe that my stroke (and my subsequent heart attack this year) is definitely liked (though indirectly) to my anosmia. I'm not saying that it is a foregone conclusion that an anosmic will eventually have a stroke or heart attack. Not all anosmics have the love of salt and fried foods that I had for nearly 50 years, so not all anosmics are morbidly obese or are hypertensive. But I think other anosmics (especially young ones) could benefit from the above cautionary tale, which is why I have shared it here.

Introducing RSLancastr! Created by RSLancastr
Last updated 26 Nov 2011, 04:23 AM

Posted by RSLancastr
26 Nov 2011, 04:23 AM

Hello all. My name is Robert S. Lancaster. I was one of the moderators at The Congenital Anosmia Forums (www.Anosmia.net) before it got shut down in 2008. I'm a 53-year-old man, living in Salem, Oregon with my wife Susan. What follows is a post I created on another, non-anosmia-themed forum, to explain to those there about my anosmia. I am posting it here to get the reactions of fellow anosmics. ====================================== MY ANOSMIA I am congenitally anosmic. This means I was born without a sense of smell. I have not smelled anuthing in my life. Ever. Here is a FAQ, based on the usual questions I am asked when a person learns this about me: ========== FAQ ========== Q: You can't smell ANYTHING? A: No, I can't. Q: What about perfume? A: No. nothing. Q: Flowers? A: Nothing. [b]Q: Dog poop? A: Nothing. Not. a. thing! (This sometimes goes on and on, with the questioner listing what are, evidently, fouler and fouler smelling things, with them usually ending with something like Q: What about a broken sewer line? A: NOOOOO!!!!! There have been times when people have stuck something under my nose saying "This smells so bad you have to be able to smell it!!" I wonder if these people ever place, say, an awful painting in front of a blind person and say "This is so ugly you have to be able to see it!!" Q: What about smelling salts? A: Oddly enough, you really don't "smell" smelling salts. it is a fume which is not sensed by your olfactory (smelling) senses, but by centers higher up in the brain. So I will react to smelling salts, but no, I don't smell them. Neither do you, as I understand it. Q: So then you cannot taste either, right? A: wrong. taste and smell are two different senses. Taste consists of Sweet, Sour, Bitter, Salty and Umami. Q: What is Umami? A: It is best described as "Meaty" or "Savory." It is the taste of MSG. Anyway, you do not need a sense of smell to taste Sweet, Sour, Bitter, Salty or Umami. For instance, even if your nose was so stuffed up you couldn't smell anything, you could still taste the difference between a spoonful of sugar and a spoonful of salt, couldn't you? Q: Yes, but what about... A: The thing is, you probably think that a person needs a sense of smell to taste things because things taste very different to you when you have a stuffed-up nose, right? Q: They do! So why... A: you are confusing Taste with Flavor. Q: Huh? A: Taste, again, consists of Sweet, Sour, Bitter, Salty and ... [b]Q: Unami. A: UMami. right. Q: So what is "Flavor?" A: The Flavor of food consists of its Taste (Sweet, Sour, etc.), Temperature, Texture (wet/dry, crunchy/soggy, smooth/lumpy, etc.) and Aroma. And, you have roughly a thousand times more olfactory (smelling) sensors than you do taste buds, so Aroma plays a HUGE role in flavor to you. So, while my sense of Taste is as good as yours - maybe better - My appreciation of Flavor is severely blunted compared to yours. Q: What did you mean, your sense of taste may be better than mine? A: May be. You've heard it said that blind people sometimes develop more accute hearing to compensate? Q: Yes, but... A: Well, that may be an Urban Legend perpetrated by popular culture, but if there is any truth to it, it seems feasible that an anosmic person might compensate for their lack of a sense of smell by developing a keener sense of taste. I know of no studies done on this though. Q: When/How did you learn you were missing your sense of smell? A: typed in a long answer but lost it. will retype it later. Forumites: any questions? I will be glad to answer them. I didn't even know the word for the condition until around 2000, when I did a web search for "no sense of smell" and found anosmia web sites. One which I found was The Congenital Anosmia Forums (anosmia.net). Not only did I now know the word for what I had, but I found a whole community of others who had the same condition! I had never met another congenital anosmic, and it was fascinating to read their stories, many similar to my own. I ended up being a moderator there, and was until the site shut down for reasons unknown to me while I was in the hospital following my stroke.

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born with congenital anosmia. Same as my mother and my maternal great-grandfather.

 

Also recently diagnosed with Ankylosing Spondylitis
My name is Robert S. Lancaster. I was a moderator at the Congenital Anosmia Forums at www.anosmia.net before it shut down in 2008.
I am patiently awaiting the day that the scented candle industry tanks.

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Anosmia.net - What happened?

Created by RSLancastr | Last updated 27 Nov 2011, 03:25 PM

My Stroke

Created by RSLancastr | Last updated 26 Nov 2011, 05:12 AM

Introducing RSLancastr!

Created by RSLancastr | Last updated 26 Nov 2011, 04:23 AM


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