Photo-onycholysis is a rare phototoxic reaction, which occurs due to the separation of the nail plate from the nail bed after a drug ingestion and exposure to ultraviolet (UV) light.
The final diagnosis was drug-induced (diclofenac) photo-onycholysis.
Photo-onycholysis can occur due to loss of nail bed-plate adhesion because of damage to the nail bed epithelium with epidermolysis and/or with formation of hemorrhagic bulla.
Photo-onycholysis is usually drug-induced, but it might occur in some photosensitivity disorders such as porphyria.
The most frequently cited drugs that cause photo-onycholysis are tetracyclines, psoralens, and fluoroquinolones.
3) The action spectrum of photo-onycholysis is mostly in the UVA wavelength.
2,7) The pathogenesis is still unknown and to get photo-onycholysis we might need a long period of intense sunlight exposure.
The rate of photo-onycholysis for tetracyclines is as follows: demecycline > doxycycline > tetracycline > minocycline.
The diagnosis of photo-onycholysis is almost clinical and can be made by exclusion of onycholysis which can be seen in other dermatologic diseases such as fungal infection, lichen planus, psoriasis, histiocytosis, atopic dermatitis, contact dermatitis, ectodermal dysplasia, collagenosis, dysthyroidism, bronchiectasis, yellow nail syndrome, iron deficiency anemia, multiple myeloma, and neoplasia.
Treatment of photo-onycholysis is unnecessary, as it disappears spontaneously after discontinuation of the suspected drug and the nails regenerate within three to six months.
Re-ingestion of the offending drug does not necessarily cause a recurrence, as drug intake should be combined with intense sun exposure to induce photo-onycholysis.