plate, associated or not with acanthosis.7 Oiso et al22 suggested the pathogenesis may be related to a deficiency in the regulation of the production of the horny layer of the nail isthmus region.
The treatment has been considered complex, regardless of the underlying cause of PIU, with poor response to topical therapies such as keratolytics and corticosteroids.23 The best therapeutic suggestion is to remove the causative agent identified.
6,23 Our hypothesis is that in PIU there is no parallelism between the nail plate and nail bed growth. However, the cause of this discrepancy of growth is uncertain, as few cases have been reported and there are many causes associated with it.
Therefore, because of the risk of association with systemic diseases and the good therapeutic response achieved in this case, we suggest the use of a flowchart for screening patients with other disorders, treatment of associated diseases, follow-up, and establishment of therapeutic proof (Figure 3).
Because of the risk of progression of systemic diseases, the patients must be followed, including, when necessary, enlisting
the assistance of other medical specialties. Our patient did not present with any clinical and/or laboratory signs of collagen disease or any other systemic diseases. This finding reinforces the hypothesis of an idiopathic condition.
Our case has a clinical importance for its impressive and excellent
response to the treatment established. The knowledge of possible PIU etiologies and therapeutic methods is crucial for the dermatologist in order to appropriately investigate comorbidities
and immediately relieve the pain and discomfort manifested by the patient.
In idiopathic cases that fail to respond to local hydroxypropyl chitosan, a surgical technique provides relief from pain. After avulsion of 5 to 6 mm of the distal nail plate, a strip of nail bed and hyponychium 3 to 4 mm wide is resected and replaced by a split-thickness graft.24
In conclusion, our good result using simple topical treatment now needs to be confirmed.