Anosmia is the loss of the sense of smell. Some people have congenital anosmia, meaning they were born without the ability to detect odors. Other times, people develop anosmia as a result of other disorders. In some diseases, such as allergies or colds, the anosmia is only temporary. But there are other diseases where it may not be reversible.
Chronic Rhinitis
Rhinitis is the inflammation of the mucous membrane in the nose. People with rhinitis usually have a congested nose, low-grade fever, runny nose, cough and sneeze. If the rhinitis lasts for a long period of time, this is referred to as chronic rhinitis. It is usually the result of a long-term inflammation or viral infection of the nose, according to Marvin Fried, M.D., chair of the Department of Otorhinolaryngology--Head and Neck Surgery at Albert Einstein College of Medicine in The Merck Manual for Healthcare Professionals. Those with chronic rhinitis can have anosmia because the mucous membrane gets larger and there is an increase in blood flow. This can interfere with odors reaching the nerve cells that pass on information about smell to the brain.
Kallman Syndrome
Kallman syndrome is a hereditary disease that usually affects boys. They have a defect in a KAL gene on chromosome 22. Their symptoms may include neurological problems, kidney problems, deafness, color blindness and a cleft palate. But they also detect fewer smells or have a total loss of smell. The olfactory nerves pass information about smell to the olfactory bulb in the brain. People with Kallman syndrome have an underdeveloped olfactory bulb or one that did not develop at all, explains Shlomo Melmed, M.D., associate dean at the David Geffen School of Medicine at UCLA in Harrison's Principles of Internal Medicine. If the olfactory bulb is underdeveloped, people detect fewer smells than normal. If it did not develop at all, they have anosmia.
Wegener's Granulomatosis
This is a vasculitis, or the inflammation of a blood vessel. One person in every 25,000 people has Wegener's granulomatosis, writes Carmen Gota, M.D., of the Cleveland Clinic Foundation in The Merck Manual for Healthcare Professionals. There is inflammation in the capillaries of the kidneys, and inflammation and granulomas in the lungs. Granulomas are groups of white blood cells that have changed to a different form surrounded by cells that are part of the immune system. People with this disorder may also have infections in their ears and sinuses. They may have anosmia if the inflammation of this disease affects the lining of the nose or the olfactory nerves.
Parkinson's Disease
Elizabeth Corwin, Ph.D. writes in the Handbook of Pathophysiology that Parkinson's disease is the result of low levels of dopamine in the substantia nigra area of the brain. Dopamine is a chemical that the nerves use to send signals. For people to be able to move in a normal way, dopamine and another chemical called acetylcholine must be in balance with each other. This balance is not achieved in persons with Parkinson's disease. The symptoms include slow movements, tremors when a limb is not moving, rigid movements and a very unstable posture. They may also have anosmia if there are changes in the olfactory bulb.
References
- "Handbook of Pathophysiology"; Elizabeth Corwin, MSN, Ph.D., FNP; 2000
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
- The Merck Manual for Healthcare Professionals: Rhinitis
- The Merck Manual for Healthcare Professionals: Wegener's Granulomatosis
