Dermatology free essay sample

Basal layer: it is where we have mitosis, and then the cells will migrate to the layers above. Prickle cell layer (spinous or squamous). * Granular layer. * Horney layer: it is the uppermost layer in the skin, and it is the layer that we see and touch on the surface of the skin, and it is composed of dead cells that had lost their nuclei. As you can see in the picture that the basophilic structures (the nuclei) are not present in this layer. Although the horney layer has dead cells, it is an important layer in the epidermis because it forms a physical barrier line to protect the internal environment. So problems and diseases affecting the horney layer will impair this protecting function leading to infections, allergies†¦ This is how the skin looks under the microscope. The bulk of the skin is dermis; 9/10th of the skin is dermis, and the bulk of dermis consists of collagen (mostly type 1 collagen). The blue things are the nuclei, and the horney layer is devoid of nuclei. And this is the normal basket-weave appearance of the skin. Epidermal cells: * Keratinocytes: the majority. Melanocytes: they are the color-producing cells in the epidermis that produce melanin which is then transferred to keratinocytes. Melanin absorbs UV light and inactivates it, otherwise we have a risk of having cancer. So western communities that have a white skin color (low activity of melanocytes) are more prone to have skin cancers, and the most common type of cancer in the western community is skin cancer; in particular the basal cell carcinoma. * Langerhans cells: they are the macrophages of the skin, and the predominant antigen-presenting cells in epidermis and dermis. And as we know, macrophages have different names in different tissues; in the liver they are called kupffer cells, and in the brain they are called microglial cells. Their function is to take the antigens, process them, and then present them to T lymphocytes, and then they go to the lymph nodes where their action starts. * Merkel cells: they are modified transducers for fine touch. The dermis: The dermis consists of several components: * Fibers (collagen and elastin). * Ground substance (glycosaminoglycans) that hydrates the skin. Several types of cells: Fibroblasts (they produce collagen and elastin), Lymphocytes, Macro, Mast cells†¦ * And it has appendages; Glands like sebaceous glands that produce sebum that moisturizes the skin, Apocrine and Eccrine glands that produce sweat that has a function in the thermoregulation of the body; Hair follicles, and Nails. * Also we have supportive structures; nerves, lymphatics, vasculature, smooth muscles. So if a lesion bleeds, then we k now that the pathology is in the dermis. Now, how do we approach patients with a skin disease? * Don’t be shy to introduce yourself as a medical student! Only few of your previous colleagues in the school could get into the medical school, so be proud to say to the patient that I’m a medical student 🙂 * Believe it or not, you can establish a connection with the patient by breaking the ice with saying these few words. So it is important for you to identify yourself, so that the patient knows your name and sees your face to have a more personal relation. * Then you take the permission to touch the skin, this is the polite way! Some patients may reject that and say â€Å"NO†, so you should respect that and say â€Å"thank you†. * Also you should always maintain the patient’s privacy. Now you have to take the patient’s story, and the first thing you have to think of is to take the chief complaint of the patient. When we say that the patient has rash, this means that the patient has multiple red things with or without scale. And when the patient says that he has a lesion, this means one or few things. And the patient may have other complaints like hair loss, blisters, color change †¦ etc. After you identify the chief complaint, you have to do a quick analysis of the chief complaint: * Onset and progression. * Modifying factors. * Symptoms: the most common symptom in dermatology is itching. Some itches may be painful. And this has a diagnostic indication, for example, herpes zoster infection is a famous painful infection. * In patients who present with rashes, we have to inquire about previous illnesses; viral, fevers, infections, that’s because the rash may happen because of the illness. * Atopy like in patients who have aczema, asthma, or hay fever, this is only relevant if it was in the patient himself or in a 1st degree relative (father, mother, brothers, sisters), other relatives are not important. * Drugs used. Next we do a quick review to the systems and take the past medical history. In dermatology, we’re lucky that we see the disease, so we depend on a good description or a proper pathologic examination. Derm Exam (TSAD) Then we signified the TSAD exam (Type, Shape, Arrangement, and Distribution). * Type: The 1st step in doing dermatologic examination is to identify the type, it’s not that easy, so you have to know the terminologies and the definitions. We have primary lesions and secondary lesions, we call them secondary lesions if they are modified by other factors, and the main factor is the patient himself when he scratches the primary lesion, so it becomes a secondary lesion. Why is it important to identify the type? Because here is where formulating the differential diagnosis starts. If somebody describes a primary lesion as being a macule, for example, that means that there is only an alteration in the color or the texture of the skin, but no elevation, and no depth. So we only see a color change or a textural change. We call it patch if the diameter is more than 2 cm, and the macule is less than 0. 5 cm in diameter. Here we may think of a pigmentary disorder or a resolving papulosquampus condition as a differential diagnosis. Papules and plaques: means that it is solid and elevated; you can feel the lesion if you close your eyes. If they were small; less than 0. 5 cm in diameter, then we call them papules. If they were more than 2 cm we call them plaques. And when the patient has scaly papules/plaques, we call that papulosquamous condition; eczema is the commonest example on that. When having non-scaly papules/plaques (elevated and red in color), it is called reactive erythema. So the first step of formulating a differential diagnosis is by right identification of the type. So if somebody gives the right description -even if he consults the dermatologist on the phone-, he can know what he has, or at least he becomes oriented to a certain group of lesions. This is just to illustrate the types of the lesions. (Refer to slides #13 amp; 14) *Macule: you can see that there is only change in the color or the texture with no elevation. *Papule: there is an elevation but no apparent depth. *Nodule: its depth reaches the dermis. Those have diagnostic indications, like when we have a pathology of thickening in the epidermis, we think of pure skin disorders. But if it is significantly more in the dermis (the pathology is more in the dermis) where we have blood vessels that may bring diseases from elsewhere in body, so we think of systemic causes. *Pustule: it is accumulation of pus with a diameter less than 0. 5 cm. *Plaque: it is a solid elevation of the skin that is more than 2 cm in diameter. *Scale: it is when there is an increase in the mitosis level of the basal cells, so lots of cells are going to the surface. Cells on the surface have to be desquamated (shed). Normally, we shed cells without realizing that, because cells are shed as single cells (each cell on its own). But when we have hyper-proliferation, the shedding will be in sheets (millions of cells together); this will be visible as a scale. Scales are a hallmark of a group of lesions called papulosquamous conditions. * Shape: Here we give more details of the primary lesion concerning the color, surface, and margins. * Color: * If a lesion is red in color, this means there is blood. [The only thing in the human body which gives a red color is blood (hemoglobin in RBCs)]. This blood can be inside the blood vessels (dilated blood vessels because of inflammatory mediators like Histamine) or hemorrhage (extravasation as in vasculitis or bleeding tendency). * If a lesion is brown or black in color, there is either increase in melanin or increase in the amount of melanocytes. This has good diagnostic implications. * Yellow color comes from carotin. Carotin is present mainly in the subcutaneous fat and to some extent in the horney layer. So there are only three natural colors (pigments) in the skin: brown or black (from melanin), red (from RBCs), and yellow (from carotin). If there is excess pigment of any of them, it will give the predominant color. * Surface: When we look at the surface of the primary or secondary lesion, we have to see whether it is scaly or not. If it is scaly, then it belongs to the papulosquamous conditions; one of the biggest groups of lesions we see. If it is non-scaly, then it belongs to the group of reactive erythemas. * Margins: Margins are either well-defined or ill-defined; and this is especially important for scaly conditions. * Arrangement: How the primary lesions are arranged together. Sometimes they can be in a line (plane warts) or in vesicles (Herpes). * Distribution: If something is generalized affecting the whole skin, we think of inflammatory conditions; they tend to be symmetrical and bilateral. If it is involving only part of the skin, we think of external causes: infection, contact allergy, or trauma. If it is on the sun-exposed parts like hands and face, we think of the sun (conditions like photodermatoses / photoaggravated dermatoses). Red non-scaly rash If a patient has a rash which is red and non-scaly, then it could be a reactive erythema. We have different types of reactive erythemas; the commonest ones are urticaria, erythema multiforme, and erythema nodosum. Vasculitis is the only one of the non-scaly erythematous lesions that has hemorrhage. The other reactive erythemas are inflammatory conditions, so they are non-scaly and associated with dilated blood vessels. If we have a red area, how do we know if it is due to hemorrhage or dilated blood vessels? We do what we call diascopy. We bring a glass slide and press it over the skin; if the color disappears, then the blood vessels are dilated and can be compressed, so its not vasculitis.