A plethora of nail changes may be seen in response to systemic disease. Beau’s lines are horizontal notches along the nails that may be caused by any major stressful event. The stressful event typically is induced by prolonged hospitalization, which causes temporary inadequate production of the nail bed by the nail matrix. It is entirely corrected spontaneously as the individual improves. Mees’ lines are induced by heavy metal toxicity, most commonly from arsenic exposure. They appear as a single, white horizontal band across each nail. Mees’ lines have also been reported in cases of malnutrition. Terry’s nails is the name given to nail changes seen in congestive heart failure and cirrhosis of the liver: More than two thirds of the proximal nail plate and bed appear dull white with loss of the lunula. Half-and-half nails, also called Lindsay’s nails, are seen in patients with chronic renal failure. The proximal half of the nail is normal appearing, whereas the distal half has a brown discoloration. Yellow nail syndrome manifests with all 20 nails having a yellowish discoloration and increased thickness of the nail plate. This syndrome is almost always seen in association with a pleural effusion, often secondary to a lung-based malignancy. Koilonychia is one of the most easily recognized deformities of the nail; it is caused by iron deficiency. The nail plate develops a spoon-shaped, concave surface. Splinter hemorrhages may be a sign of bacterial endocarditis. Clubbing, which is defined as loss of Lovibond’s angle, is typically caused by chronic lung disease. The nail unit can manifest disease in many ways, and awareness of the various nail signs can help the clinician diagnose and treat these conditions.