Nails can be an indicator of local and systemic disease. There can be stunted growth, and they may be brittle and deformed. Nail biters (figure 16) can be identified from loss of the projecting nail in any of the digits of either hand. Whitish spots under the nail (leukonychia punctata) are associated with minor trauma. Pallor of anemia and hypoalbuminemia, cyanosis and polycythemia are usually well shown, and pitting of the nails is common in psoriasis. Splinter hemorrhages are longitudinal brown strips along the length of the middle of the nail, they are found in bacterial endocarditis and vasculitic disorders. Spoon- shaped, central depression of the nail (koilonychia), is seen in iron deficiency anemia.
Transverse grooves at a similar level in a number of nails (Bau’s lines) can denote growth abnormalities related to the onset of a severe systemic disease. The arch over the base of the nail may become brown (Mei’s lines) in renal insufficiency, poisoning and some inflammatory disorders. Infections around the nail (paronychia – figure 17) are common but always exclude a diabetic etiology.