There are numerous diseases with which<unk>  is associated. In a case study, Frasnelli et al. examined five patients that endured<unk>  or phantosmia, most as a result of upper respiratory tract infections (URTIs). It is hypothesized that URTIs can result in<unk>  because of damage to olfactory receptor neurons (ORNs). The condition has been linked to coronavirus disease 2019 as a rare side effect. Exposure to harmful solvents has also been linked to<unk> , specifically by damaging ORNs. Damage to these neurons could render them unable to correctly encode a signal representing a particular odor, which would send an erroneous signal to the odor processing center, the olfactory bulb. This, in turn, leads to the signal triggering a different smell than the stimulating odor, and thus the patient cannot sync the input and output odors. Damage to ORNs describes a peripheral defect in the pathway, but there are also instances where damage to the processing center in the brain can lead to distorted odors. Different types of head trauma could also lead to dysfunctions that relate to what the afflicted brain area controls. In humans, the olfactory bulb is located on the inferior side of the brain. Physical damage to this area would alter how the area processes information in a variety of ways, but there are also diseases that can alter how this area works. If the part of the brain that interprets these input signals is damaged, then a distorted output is possible. This would also lead to<unk> . Temporal lobe epilepsy has led to cases of<unk> , but these were only temporary; the onset of<unk>  was a seizure and it typically lasted a week or two after.<unk>  is sometimes associated with Parkinson's disease. Although the specific pathway is undetermined, the lack of dopamine has resulted in documented cases of<unk>  and phantosmia.
Parosmia
Raccoon eyes
Xerophthalmia
Macular telangiectasia
Macrodontia 
Copper beaten skull
Chromonychia
Paronychia