Table 4.

Causes of melanonychia compared with those of subungual bleeding

Melanonychia	Subungual bleeding
Benign racial melanonychia	Direct trauma
Laugier Hunziker	Indirect microtrauma-end on repetitive trauma
Inflammation	Haemorrhagic tendency lowering threshold for effects of trauma. eg
• Lichen planus	• warfarin
• Chronic paronychia	• leukaemic
• Trauma/friction	• thrombocytopaenia
• radiation
Medication e.g.	Subungual tumour
• Minocycline	• squamous cell carcinoma
• Chemotherapy	• wart
• HIV disease or medication	• exostosis
	• melanoma
	• pyogenic granuloma
Addison's disease
Peutz Jeghers
Subungual naevus
Benign melanocyte activation
Melanoma
Bowen's disease (in situ squamous cell carcinoma)
Onychomycosis