Nail diseases are distinct from diseases of the skin. Although nails are a skin appendage, they have their own signs and symptoms which may relate to other medical conditions. Nail conditions that show signs of infection or inflammation require medical assistance and cannot be treated at a beauty parlor. Deformity or disease of the nails may be referred to as onychosis.

Color change of the nails suggests:

Terry's (white) nails-
Hepatic failure, cirrhosis, diabetes mellitus, CHF, hyperthyroidism, malnutrition
Azure lunula
Hepatolenticular degeneration (Wilson's disease), silver poisoning, quinacrine therapy
Half-and-half nails
Specific for renal failure
Muehrcke's lines
Specific for hypoalbuminemia
Mees' lines
Arsenic poisoning, Hodgkin's disease, CHF, leprosy, malaria, chemotherapy, carbon monoxide poisoning, other systemic insults
Dark longitudinal streaks
Melanoma, benign nevus, chemical staining, normal variant in darkly pigmented people
Longitudinal striations
Alopecia areata, vitiligo, atopic dermatitis, psoriasis
Splinter hemorrhage
Subacute bacterial endocarditis, SLE, rheumatoid arthritis, antiphospholipid syndrome, peptic ulcer disease, malignancies, oral contraceptive use, pregnancy, psoriasis, trauma
Telangiectasia
Rheumatoid arthritis, SLE, dermatomyositis, scleroderma

proximal edge of the nail bed) disappears, and the nail takes on a yellow hue.
FIGURE 1. Anatomic structures of the nail.