58
Nail Disorders
• The nail matrix, which is the growth area, has proximal and distal components (Fig. 58.1).
– The proximal nail matrix forms the top (surface) of the nail plate.
Fig. 58.1 Nail unit anatomy.
• Fingernails grow ~1 mm per month and are replaced every 6 months.
• Toenails grow ~0.5 mm per month and are replaced every 12 months.
Onycholysis
• Distal nail plate detachment, causing nail to look white to yellow-white (Fig. 58.2).
Fig. 58.2 Causes of onycholysis. *Due to secondary colonization with Pseudomonas aeruginosa. SCC, squamous cell carcinoma; TFTs, thyroid function tests.
• Chronic exposure to water and irritants (e.g. soaps) is a common cause.
• Associated with psoriasis, onychomycosis, hyperthyroidism, and medications (Table 58.2).