There are numerous reports showing the association between titanium and yellow nail syndrome in addition to the above reports. In 2015, Decker et al. reported a case of a 67-year-old female patient who had lost her claws 18 months prior and had changes in bronchitis, sinusitis, and nails within the last 5 years. Inhaled corticosteroids were used for initial continuous cough symptoms but were not effective. These early respiratory symptoms were followed by changes in nails 3 years later. At the same time, Pseudomonas aeruginosa bronchitis and sinusitis were experienced. Lymphedema was not observed, and vitamin E 1600 IU/day treatment was prescribed. EDXRF of the nails revealed high levels of titanium; eight amalgam restorations and fluoride-containing toothpastes were used daily in the oral cavity. She was also reported to have a history of regular titanium dioxide intake through cetirizine (10 mg/day) and gum (4–8 piece/day). Ataya et al. reported a 56-year-old woman with appearance of yellow nail syndrome symptoms immediately after implantation. Chronic sinusitis, cough, a change in nails, and maxillary sinusitis were all recovered after implant removal. However, they reported that there was no change in the nails. This report also showed that yellow nail syndrome was associated with titanium. Dos Santos also reported the association of yellow nail syndrome with titanium in 2016, and De Lima and Dos Santos et al. reported the observation of titanium accumulation in the liver, spleen, lung, lymph nodes, and bone marrow in the autopsy results of five drug-addicted patients; titanium pigmentation was observed under a microscope. This report revealed a systemic accumulation of titanium, but with no change in the nails.

As in the aforementioned reviews, the accumulation of titanium has been observed in patients with “yellow nail syndrome” and the relationship is currently being discussed in greater detail. There have been several reports of the relative association between titanium and yellow nail syndrome at the beginning of Berglund and Carlmark’s report; on the contrary, there was no evidence of “yellow nails” in the anatomical studies of patients who were drug addicted. This is still a controversial topic which is still in debate. Therefore, further studies are needed to determine the relationship between titanium and yellow nail syndrome and the pathogenesis.