Abstract
Diagnosis of cutaneous lesions requires both history taking and physical examination. History taking must specify the circumstances of the onset and the course of the disease, as well as treatments applied and their effects. The starting date of the disorder and its initial location must be specified, as well as the ways in which the lesions spread and eventually change. The main cutaneous functional symptoms are pain and pruritus. The context in which lesions have appeared is often essential: associated extracutaneous signs, medications, comorbidities, immunodeficiencies, etc. Thus full history taking is often crucial, gathering all past history. Finally, given the large number of skin diseases related to the environment, targeted history taking should be carried out regarding lifestyle, professional and domestic backgrounds, and products that may have been applied and manipulated, in order not to miss, for example, the diagnosis of a contact dermatitis. Dermatological physical examination requires training. It is necessary to know how to recognize the primary lesions of the skin, their arrangement and/or configuration, and their distribution.
Diagnosis of cutaneous lesions requires both history taking and physical examination. History taking must specify the circumstances of the onset and the course of the disease, as well as treatments applied and their effects. The starting date of the disorder and its initial location must be specified, as well as the ways in which the lesions spread and eventually change. The main cutaneous functional symptoms are pain and pruritus. The context in which lesions have appeared is often essential: associated extracutaneous signs, medications, comorbidities, immunodeficiencies, etc. Thus full history taking is often crucial, gathering all past history. Finally, given the large number of skin diseases related to the environment, targeted history taking should be carried out regarding lifestyle, professional and domestic backgrounds, and products that may have been applied and manipulated, in order not to miss, for example, the diagnosis of a contact dermatitis. Dermatological physical examination requires training. It is necessary to know how to recognize the primary lesions of the skin, their arrangement and/or configuration, and their distribution.
Primary lesions are the skins response to aggressions and diseases. The term elementary lesions , which clearly reflects the fact that those lesions are the basic response patterns of the skin, is used in the French dermatologic literature. Every skin disorder can be described by means of its constitutive primary lesions. Therefore, a limited set of lesions describes all skin disorders. These lesions can thus be compared to the letters of the alphabet. Their combination produces syndromes.
The arrangement is the positioning of the various lesions relatively to each other. For example, they can form a line (linear arrangement) (Fig. ).
Configuration indicates the shape of an isolated primary lesion. For example, a lesion can be annular (Fig. ).
Distribution indicates the spread of the disease that is the parts of the body where the lesions are located. For example, it may be a single, thus localized lesion, as is the case in tumors; it may also be a generalized eruption affecting the entire skin, for example, in certain drug reactions or virally induced eruptions.
In practice, two types of situations can be pointed out: common situations (acne, warts, etc.) or single lesions (tumors) and more complex situations. In the first case, it may be useful to quickly proceed to a physical examination. In all the other cases, it is preferable to begin with history taking since the precise history of the disease, the personal and family histories, and the review of systems provide essential and even indispensable information for proper diagnosis. Indeed, it must be borne in mind that almost all diseases can induce cutaneous manifestations, which can sometimes help reveal them. This implies taking into account the whole history and all other clinical signs (history taking and physical examination data) in making a diagnosis.
The reasoning mechanisms that allow making a diagnosis based on visual analysis are twofold:
An analogical mechanism, where the physician recognizes a disease he has already observed
An analytical mechanism, in which the physician recognizes one or more primary lesions with their distribution and/or configuration and/or arrangement and/or evolution enabling him to make one or more diagnoses, without necessarily having observed this dermatosis beforehand
It is necessary to keep in mind the following points:
The semiological analysis of the cutaneous lesions must always be considered in the general context of the patient: his/her medical history, the complete history of his/her disease, other clinical signs, etc. Otherwise, there is high risk of either making a wrong diagnosis or ignoring the causality.
One should avoid confusion between semiology (study of signs) and nosology (study of diseases). Papules, for example, have many causes including urticaria. Urticaria, for instance, corresponds to nosology since it can be the cutaneous expression of many different diseases. Urticaria can occur, for example, in a patient with thyroid dysfunction or as a result of drug allergy. Similarly with comedo, its identification requires a careful semiological approach. Interpretation is based on nosology since the causes of comedo are varied. The most common cause is acne; however, the following conditions may also be comedonal: follicular mucinosis and mycosis fungoides, lupus erythematosus, heliosis (Favre-Racouchot syndrome), follicular form of Dariers disease, drug eruption and intoxication (dioxin, amineptine, etc.), nevus comedonicus, facial papules occurring in certain B cell blood dyscrasias, etc.
Always list all the existing primary lesions, their configuration, arrangement and distribution, as well as their history. It is also necessary to specify the context in which these lesions appeared, the associated extracutaneous signs, and the history of the patient.
Fig. 1.1
Dermatomyositis. Linearity. Palpable linear erythema of the back of the hands. The general rule is that linearity results from the action of an external agent. Here, dermatomyositis is an exception to this rule since it is an endogenous disease which causes the linear erythema, extending from the back of the hand to the dorsal aspect of the fingers. Dermatomyositis is a serious disease affecting the skin, muscles, and sometimes the lungs, digestive tract, and other organs. Treatment is based on systemic corticosteroids sometimes combined with immunosuppressants
Fig. 1.2
Herpes. Herpetiformis. Several liquid lesions (called vesicles) on a red background and close to each other. In this example, the arrangement of these lesions is said to be herpetiform, since it is characteristic of herpesvirus infections. Two other signs characterizing vesicles of viral origin can be observed: the specific gray color and most importantly the central subsidence of several vesicles, called umbilication