Olfactory function in Wilson's disease-systematic literature review.

In Wilson's disease (WD) improper copper metabolism results in copper accumulation in various organs, mainly brain and liver. The sense of smell is today one of the focuses of interest in aging and neurodegenerative diseases research. However, in WD olfactory function (OF) is still poorly investigated. Our aim was to perform a systematic review of the studies evaluating OF in WD. We searched PubMed for original papers evaluating olfactory function in WD and retrieved five articles. Additionally, one article was identified while viewing the references lists of the included studies. Finally, we included 6 studies. The number of patients ranged from 12 to 68 (altogether 222 WD patients) and their clinical characteristics were variable. Differences in methodology (mainly various tests used for OF evaluation) made it impossible to meta-analyze the data. OF was worse in WD than in controls in all studies. In 3 studies OF was impaired significantly in neurologic phenotype vs hepatic, which was not confirmed in 2 other studies. Correlation between OF and presence of brain lesions in magnetic resonance imaging was inconsistent across two studies. Only one study assessed brain regions involved in the olfactory tract by evaluating olfactory bulb volume. There was no effect of WD treatment, including its type and duration on OF (4 studies). One study additionally assessed taste which was preserved in WD. Although OF was found to be abnormal in WD, this area remains insufficiently explored. Further studies conducted on larger cohorts, with a focus on olfactory tract damage, is essential.