General Features Of The Skin

COLOR Skin color represents an aggregate of the remitted and reflected light, the wavelengths of which depend largely on the presence of four biochromes. Two biochromes are in the epidermis: melanin , which is brown and has a broad absorption in the ultraviolet and visible light ranges, and carotenoids, which are yellow. Two other biochromes are in the dermis: oxyhemoglobin, which is bright red and is found largely in the arterioles and capillaries of the papillary layer, and reduced hemoglobin, which is bluish red and is found in the subpapillary venous plexus. The dermal connective tissue may also contribute to the “whiteness” of the skin in lightly pigmented persons. 

General Features of the Hair and Nails

The distribution of the body hair, its texture, and amount should be noted as a part of the initial overall survey of the patient's skin, as should examination of the nails. The nails  can provide evidence of latent skin disease (psoriasis, lichen planus, alopecia areata, congenital ectodermal defect), as well as suggest the presence of renal or liver disease. Beau's lines (transverse indentations of the nails) and other variations on the theme of transverse white lines across the nails may be associated with a recent febrile or systemic illness, especially a renal or hepatic one. Telangiectasia in the periungual skin is a frequent and important diagnostic finding in systemic lupus erythematosus and dermatomyositis. 

General Features of the Mucous Membranes 

The initial general assessment of the patient must also include the oral, genital, and anal regions. The oral mucous membranes indicate the state of hydration and show pigmentary changes that can be racial traits or that may be helpful in the diagnosis of Peutz-Jeghers syndrome and Addison's disease. Among the many skin diseases that have mucous membrane manifestations are lichen planus, pemphigus, pemphigoid, herpes simplex, and erythema multiforme. The tongue may be red and smooth in various states of vitamin B deficiency. Soreness, as well as a beefy-red tongue, may be present as an initial complaint in pernicious anemia. The so-called black hairy tongue may be present as a relatively trivial problem, consisting of darkened, elongate filiform papillae that appear after the use of orally administered antibiotics or without any antecedent cause. The so-called geographic tongue consists of an irregular pattern of areas exhibiting absence of papillae; it may be associated with pustular and other varieties of psoriasis or it may be idiopathic. Lichen planus may be found on the tongue as linear white markings, sometimes in a netlike pattern. Oral thrush (moniliasis) occurs in diseases of altered immunity. Generalized monilial infections involving axillary, oral, periungual, and vaginal areas occur in the syndrome of mucocutaneous candidiasis and the syndrome of Addison's disease with hypoparathyroidism. Oral hairy leukoplakia occurs in HIV infection, often as an early sign.