Conformação pode ser uma pista
- Se origem externa → o limite proximal da manha corresponde à forma da prega posterior
- Se origem interna → o limite dista da mancha corresponde à forma da lúnula
Chromonychia due to external causes
- Occupational causes: hairdressers, photographers
- Various topical medications: silver nitrate
- Tobacco and cosmetics: henna, nail polish
- Trauma: hematoma and, sometimes, longitudinal melanocychia, which must be differentiated from melanoma, whose coloration remains abnormally fixed over time
- Mycobacterial infections: see below
- Physical agents: regional and remote radiotherapy, antitumor therapy
- Thermal burns
Chromonychia associated with systemic medications
- Antibiotics: photo-onycholysis is predominant (doxycycline, minocycline, pefloxacin)
- Psoralens
- Anti-malarials: gray-blue pigmentation of the nail bed
- Cytotoxic agens
- Blue lunulae in argyria
- Cyanosis of the nail bed due to sulfonamides
Xanthonychia syndrome or yellow nail syndrome
- Partly due to slow growth of the nail
- Treatment: vitamin E (1000 IU/day) and fluconazol (300mg once a week) → best results
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