Hyposmia, or microsmia, is a reduced ability to smell and to detect odors. A related condition is anosmia, in which no odors can be detected. Some of the causes of olfaction problems are allergies, nasal polyps, viral infections and head trauma. It is estimated that up to 4 million people in the United States have hyposmia or the related anosmia.
Hyposmia might be a very early sign of Parkinson's disease. Hyposmia is also an early and almost universal finding in Alzheimer's disease and dementia with Lewy bodies. Lifelong hyposmia could be caused by Kallmann syndrome.
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- Factor, Stewart A., & Weiner, William J., eds. (2008). Parkinson's Disease: Diagnosis and Clinical Management, 2nd ed., pp. 72-73. New York: Demos Medical Publishing.
- Arkoncel, ML; Arkoncel, FR; Lantion-Ang, FL (March 2011). "A case of Kallmann syndrome". BMJ Case Reports. 2011. doi:10.1136/bcr.01.2011.3727. PMC 3070321. PMID 22700069.
Kallmann syndrome (KS), a rare genetic disorder, refers to the association between hypogonadotropic hypogonadism and anosmia or hyposmia due to abnormal migration of olfactory axons and gonadotropin-releasing hormone producing neurons.