Clubbing is a sign of prolonged hypoxia. Causes of clubbing include emphysema, chronic bronchitis, lung cancer, and heart failure. Beau's lines (transverse depressions in the nail that extend beyond the nail bed) occur with acute illness, malnutrition, and anemia. Koilonychia (thin, spoon-shaped nails with lateral edges that tilt upward) is associated with Raynaud's disease, malnutrition, chronic infections, and hypochromic anemia. Onycholysis (loosening of the nail plate with separation from the nail bed) is associated with hyperthyroidism, psoriasis, contact dermatitis, and Pseudomonas infections.