Notes on Dermatology for Competitive Exams Part I
Dermatology is the branch of medicine that focuses on the diagnosis, treatment, and prevention of skin, hair, and nail disorders.
The skin is the largest organ of the body, and it plays a crucial role in protecting the body from external factors like heat, cold, and infections. Therefore, dermatology involves a wide range of medical and surgical treatments, as well as cosmetic procedures to enhance the skin's appearance.
Primary Skin Lesions :
Primary skin lesions are abnormalities that develop on the skin's surface and originate from the epidermis, dermis, or both. There are various types of primary skin lesions, each with different characteristics and presentations. Here are some of the most common primary skin lesions:
Macule:
A macule is a small flat spot on the skin that is less than 1 cm in diameter. It can be any color, including brown, red, or white. Examples of macules include freckles, flat moles, and petechiae (tiny pinpoint red spots caused by bleeding under the skin).
Patch:
A patch is similar to a macule, but it is larger than 1 cm in diameter. Patches can be any color and may have a different texture or thickness than the surrounding skin. Examples of patches include vitiligo (a loss of skin pigment) and port-wine stains (pink or red patches caused by blood vessel abnormalities).
Papule:
A papule is a raised bump on the skin that is less than 1 cm in diameter. Papules may be red, pink, or flesh-colored and can be caused by a variety of conditions, including acne, insect bites, and eczema.
Plaque:
A plaque is similar to a papule, but it is larger than 1 cm in diameter. Plaques are often elevated and may have a scaly or rough surface. Examples of plaques include psoriasis (an autoimmune condition that causes red, scaly patches on the skin) and lichen planus (an inflammatory condition that can affect the skin, mouth, and genitals).
Nodule:
A nodule is a solid, raised lesion that is larger than a papule, typically more than 1 cm in diameter. Nodules may be painful and can be caused by a variety of conditions, including infections and tumors.
Vesicle:
A vesicle is a small fluid-filled blister that is less than 1 cm in diameter. Vesicles may be clear or cloudy and can be caused by a variety of conditions, including herpes simplex virus infections and allergic reactions.
Bulla:
A bulla is similar to a vesicle, but it is larger than 1 cm in diameter. Bullae may be filled with clear or bloody fluid and can be caused by a variety of conditions, including bullous pemphigoid (an autoimmune condition that causes blisters on the skin and mucous membranes) and burns.
Pustule:
A pustule is a raised lesion that contains pus, typically less than 1 cm in diameter. Pustules can be caused by a variety of conditions, including acne and bacterial infections.
Petechiae:
Petechiae are tiny, pinpoint red or purple spots on the skin that are caused by bleeding under the surface of the skin. They are usually less than 2 millimeters in diameter and do not blanch or fade when pressed.
Purpura:
Purpura are larger, flat areas of bleeding under the skin that are often red, purple, or brown. They are generally larger than petechiae, usually greater than 3 millimeters in diameter, and may appear as small spots or larger patches.
Telangiectasia:
Telangiectasia are small, dilated blood vessels on the surface of the skin, often appearing as red or blue lines or clusters of fine, web-like veins. They can occur anywhere on the body and are most commonly seen on the face and legs.
Lichenification:
Lichenification refers to thickened, rough skin that develops in response to chronic irritation or scratching. It is characterized by exaggeration of the normal skin markings and a leathery, rough texture.
Wheals:
Wheals, also known as hives, are raised, itchy, red or white welts on the skin that can be round or irregularly shaped. They often appear suddenly and may disappear quickly or last for hours to days. Wheals are typically caused by an allergic reaction but can also be triggered by stress, heat, or other factors.
Secondary Skin Lesion
Secondary skin lesions are changes in the skin that result from primary lesions or from external factors such as scratching, infection, or trauma. Secondary skin lesions can provide important clues to the underlying disease process and may include:
Scales:
Flakes of skin that can vary in size and shape, often resulting from a buildup of dead skin cells. Examples include psoriasis and seborrheic dermatitis.
Crusts:
Dried exudate or blood on the surface of the skin, often caused by infection or trauma. Examples include impetigo and eczema.
Scars:
Fibrous tissue that replaces normal skin after injury or surgery. Scars can vary in appearance and texture depending on the extent of the injury and the healing process.
Ulcers:
Open sores that extend through the full thickness of the skin and can result from a variety of causes, including infection, trauma, and underlying disease processes such as vasculitis.
Fissures:
Cracks or breaks in the skin that can occur in areas of dry, thickened skin. Examples include fissures in atopic dermatitis and psoriasis.
Atrophy:
Thinning of the skin that can result from aging, long-term use of topical steroids, or underlying medical conditions such as connective tissue disorders.
Excoriations:
Scratches or abrasions on the skin that result from scratching or rubbing. Excoriations can occur in a variety of skin conditions, including atopic dermatitis, scabies, and prurigo nodularis.
Carcinoma of Skin
Basal cell carcinoma:
Risk factors:
Exposure to UV radiation, fair skin, history of sunburns, family history of skin cancer, and a weakened immune system.
Diagnosis:
A biopsy is usually done to confirm the diagnosis. The doctor will remove a small sample of the suspicious skin tissue and examine it under a microscope.
Treatment:
Surgery is the most common treatment option, which involves removing the cancerous tissue. Other treatments include radiation therapy, topical medications, and cryotherapy.
Prognosis:
Basal cell carcinoma is generally curable with early detection and treatment. The prognosis is excellent, with a very low risk of recurrence or spreading to other parts of the body.
Squamous cell carcinoma:
Risk factors:
Exposure to UV radiation, fair skin, history of sunburns, exposure to chemicals or radiation, and a weakened immune system.
Diagnosis:
A biopsy is done to confirm the diagnosis. The doctor will remove a small sample of the suspicious skin tissue and examine it under a microscope.
Treatment:
Surgery is the most common treatment option, which involves removing the cancerous tissue. Other treatments include radiation therapy, topical medications, and cryotherapy.
Prognosis:
Squamous cell carcinoma is usually curable with early detection and treatment. The prognosis is generally good, but if the cancer has spread to other parts of the body, the prognosis may be more guarded.
Melanoma:
Risk factors:
Exposure to UV radiation, fair skin, history of sunburns, a family history of melanoma, and a weakened immune system.
Diagnosis:
A biopsy is done to confirm the diagnosis. The doctor will remove a small sample of the suspicious skin tissue and examine it under a microscope.
Treatment:
Treatment options for melanoma include surgery, chemotherapy, radiation therapy, and immunotherapy. The choice of treatment depends on the stage and location of the cancer.
Prognosis:
Melanoma can be deadly if it is not detected and treated early. However, if caught early, the prognosis is usually excellent. Advanced melanoma has a poorer prognosis, but new treatments are improving outcomes for many patients.
Merkel cell carcinoma:
Risk factors:
Exposure to UV radiation, fair skin, and a weakened immune system.
Diagnosis:
A biopsy is done to confirm the diagnosis. The doctor will remove a small sample of the suspicious skin tissue and examine it under a microscope.
Treatment:
Treatment options for Merkel cell carcinoma include surgery, radiation therapy, and chemotherapy.
Prognosis:
Merkel cell carcinoma is an aggressive cancer that tends to spread quickly to other parts of the body. The prognosis is generally poorer than other types of skin cancer, but early detection and treatment can improve outcomes.
Psoriasis
Psoriasis is a chronic skin condition that causes red, scaly patches on the skin. The lesions of psoriasis can be found anywhere on the body, including the scalp, nails, and joints. The exact cause of psoriasis is not known, but it is thought to be related to an abnormal immune response.
Clinical Findings
- Red, raised patches of skin with silvery scales
- Itching or burning sensation
- Dry or cracked skin that may bleed
- Thick, pitted or ridged nails
- Joint pain or swelling (in some cases)
Types of psoriasis:
Plaque psoriasis:
This is the most common type of psoriasis, characterized by red, raised patches of skin with silver-white scales.
Guttate psoriasis:
This type of psoriasis appears as small, drop-like lesions on the skin. It often develops after a bacterial infection, such as strep throat.
Inverse psoriasis:
This type of psoriasis occurs in skin folds, such as under the arms, in the groin area, or under the breasts.
Pustular psoriasis:
This type of psoriasis causes pus-filled blisters on the skin, which can be painful and itchy.
Erythrodermic psoriasis:
This is a rare but severe form of psoriasis that causes widespread redness and shedding of the skin.
Treatment of psoriasis:
Topical treatments:
These are the first-line treatment for mild to moderate psoriasis. They include topical corticosteroids, retinoids, coal tar, salicylic acid, and moisturizers.
Phototherapy:
This involves exposing the skin to ultraviolet light, either alone or in combination with medications. Phototherapy is effective in treating moderate to severe psoriasis.
Systemic medications:
These medications are reserved for severe cases of psoriasis that have not responded to other treatments. They include methotrexate, cyclosporine, and biologic drugs.
Lifestyle changes:
These include avoiding triggers that can worsen psoriasis, such as stress, smoking, and alcohol consumption. Regular exercise, a healthy diet, and stress-reducing techniques may also be beneficial.
Blistering Skin Lesions
Blistering skin diseases are a group of disorders that cause the skin to blister and erode. These diseases can be inherited or acquired and are characterized by a variety of clinical and pathological features.
Pemphigus Vulgaris:
Pemphigus vulgaris is a rare autoimmune disorder that causes blistering of the skin and mucous membranes. The blisters can be painful and may occur on any part of the body. Pemphigus vulgaris is caused by antibodies that attack the proteins that hold skin cells together.
Bullous Pemphigoid:
Bullous pemphigoid is a chronic autoimmune disorder that causes large blisters on the skin. The blisters can be itchy and may occur on any part of the body. Bullous pemphigoid is caused by antibodies that attack proteins in the skin and basement membrane.
Epidermolysis Bullosa:
Epidermolysis bullosa is a rare genetic disorder that causes the skin to be fragile and prone to blistering. This disorder can be inherited in an autosomal dominant or recessive manner. There are several subtypes of epidermolysis bullosa, each with different symptoms and genetic causes.
Dermatitis Herpetiformis:
Dermatitis herpetiformis is a chronic autoimmune disorder that causes small, itchy blisters on the skin. These blisters are typically located on the elbows, knees, buttocks, and back. Dermatitis herpetiformis is caused by antibodies that attack gluten in the diet.
Porphyria Cutanea Tarda:
Porphyria cutanea tarda is a rare metabolic disorder that causes blisters on the skin. These blisters are usually located on the hands and face and are triggered by exposure to sunlight. Porphyria cutanea tarda is caused by a deficiency of the enzyme uroporphyrinogen decarboxylase.
Treatment for blistering skin diseases varies depending on the underlying cause of the disorder. In some cases, medications such as corticosteroids, immunosuppressants, and antibiotics may be used to manage symptoms and prevent complications. In other cases, lifestyle changes such as avoiding triggers or following a gluten-free diet may be recommended. For genetic disorders such as epidermolysis bullosa, treatment may focus on managing symptoms and preventing complications.
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