What is a skin disease?

Skin diseases are diseases and disorders that affect human skin and have a wide range of causes. Skin abnormalities can be important indicators of underlying internal diseases, mirroring a person’s internal health, and may suggest metabolic, malignant, and glandular diseases. Skin is subject to hereditary, inflammatory, neoplastic, endocrine, hormonal, traumatic, and degenerative pathological changes. Skin disorders in children include eczema and local infections. Extensive skin inflammation can affect other organs and systems, leading to anemia, circulatory collapse, and disturbances in body temperature and electrolyte balance.

How does a skin disease affect the body's largest organ?

Skin diseases, affecting the body's largest organ, can manifest as abnormalities that signal underlying internal issues. Extensive skin inflammation can disrupt metabolism in other organs, potentially leading to anemia, circulatory collapse, and imbalances in body temperature, water, and electrolytes. Skin disorders can stem from hereditary, inflammatory, or other pathological changes. Infections from bacteria, viruses, fungi, and parasites can impact the skin. For example, bacterial infections may cause pustules, while viral infections can lead to warts or blisters. Fungal infections are a common cause of chronic skin eruptions.

What are some common symptoms of skin diseases?

Skin diseases show a range of symptoms, as they are impacted by pathological changes, such as hereditary, benign and malignant, endocrine, and inflammatory processes. Common symptoms include scaling from overproduction of epidermal cells, inflammation (redness, heat, swelling, itching), and color changes due to alterations in blood flow or melanin production. Itching is a predominant symptom caused by the release of mediators like histamine. Specific conditions exhibit distinct symptoms: * Athlete's foot can be scaly, red, and cracked, or white and moist with blisters. * Nonmelanoma skin cancer appears as unusual growths or moles that may be raised or flat, with varied colors. * Eczema and dermatitis present with swelling, blisters, thickening, and scaling of the skin, leading to intense itching. * Psoriasis is characterized by reddish patches covered with silvery scales, often on elbows, knees, and scalp. * Skin infections can cause pus-filled inflammations (boils) or chronic changes with specific cell arrangements.

What are the different causes of skin diseases?

Skin diseases arise from a multitude of factors, broadly categorized as hereditary, infections and infestations, internal diseases, and allergic reactions. Hereditary factors A person's genotype can directly or indirectly determine many common skin diseases. Sunlight or stress can activate hereditary conditions such as psoriasis and atopic eczema. Genetic abnormalities like nevi (moles or birthmarks) result from structural or numerical irregularities in skin cells. Skin infections and infestations Harmless bacteria reside on healthy skin, but pathogenic strains of staphylococci can pose a threat, especially in hospital settings. Bacterial infections can manifest as pustular infections or chronic inflammatory changes. Viral infections, such as warts, chickenpox, and shingles, invade the epidermis through abrasions, the bloodstream, or peripheral sensory nerves. Fungal infections, commonly caused by dermatophyte fungi or yeasts like Candida albicans, can lead to chronic skin eruptions. Skin infestations like pediculosis (lice) and scabies (mites) thrive in overcrowded, unhygienic conditions. Internal diseases Skin abnormalities can indicate underlying metabolic, malignant, and glandular diseases. Allergic reactions Inappropriate immune responses to harmless substances can trigger allergic reactions. Type I hypersensitivity, also known as atopic or anaphylactic hypersensitivity, involves IgE antibody, mast cells, and basophils.

How do doctors diagnose skin diseases?

Doctors diagnose skin diseases through a comprehensive approach. Initially, a medical history is taken, including details about symptoms, emotional factors, and past conditions. A physical exam follows, involving visual inspection of the skin for signs like redness, hair loss, or moles, and areas the patient can't easily see. To confirm the diagnosis, doctors use methods such as biopsies , where tissue samples are examined microscopically. There are several types of biopsies including: * Needle biopsy * Excisional biopsy * Incisional biopsy In some cases, doctors use imaging technologies, optical scopes, and other tests. The skin's reaction to diseases can mirror internal health, making it vital in diagnosing systemic issues.

How can understanding skin disease pathology help in treating and preventing these conditions?

Understanding the pathology of skin diseases is vital for both treatment and prevention. Skin abnormalities can signal underlying metabolic, malignant, or glandular issues, acting as a mirror to a person’s internal health. Examining how skin diseases appear, are distributed, and affect the skin helps in diagnosis. For instance, inflammation, a key feature of many skin conditions, results from chemical mediators and can be countered with treatments like antihistamines. Understanding the specific causes and patterns of skin diseases allows healthcare providers to implement targeted treatments and preventive measures, improving patient outcomes and overall health.

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skin disease

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Malcolm W. Greaves

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History

General features

Although most diseases affecting the skin originate in the layers of the skin, such abnormalities are also important factors in the diagnosis of a variety of internal diseases. There is some truth in the belief that the skin mirrors a person’s internal health. Often, the visibility and accessibility of skin make it the first organ of the body to show detectable signs of underlying disease. Abnormalities of the skin frequently suggest metabolic, malignant, and glandular diseases.

Like other tissues, skin is afflicted by all types of pathological changes, including hereditary, inflammatory, benign and malignant (neoplastic), endocrine, hormonal, traumatic, and degenerative processes. Emotions affect the health of the skin as well. The reaction of the skin to these diseases and disorders differs from that of other tissues in many ways. For example, extensive inflammation of the skin may affect metabolism within other organs and systems of the body, causing anemia, circulatory collapse, disorders of body temperature, and disturbance of water and electrolyte balance in the blood. The skin has such vigorous healing properties, however, that widespread injury, as in thermal burns, may be followed by a marked degree of regrowth of the injured or diseased areas, with a disproportionally small degree of scarring.

Diagnosis

The skin has an inherent region-specific anatomical diversity that may profoundly modify the appearance of a rash. This is apparent when skin transplanted from one area of the body to another (other than a symmetrically opposite area) retains the morphological characteristics of the donor area. Thus the morphology of eczema or lichen planus on the palms and soles may bear little or no resemblance to the same disease in the same individual on the face or scalp. In these instances a biopsy shows the abnormalities of the cells of the skin and the pattern and distribution of any invading cells. The ability to identify immunoreactants (immunoglobulins, or antibodies, that react with specific invading agents, or antigens) in skin biopsies has greatly increased the accuracy of the diagnosis of inflammatory disorders and has clarified their immunologic basis, especially in the blistering disorders.

The classification of hereditary skin disorders generally has been based upon gross morphological, histological, and electron microscopic findings; however, because a skin disease may not always have a characteristic presentation, the specific diagnosis sometimes has been in doubt. Better understanding of the biochemical defects underlying hereditary skin disorders now allows these conditions to be diagnosed with more precision. One subset of the ichthyoses, a group of sometimes disabling genetic skin disorders, may thus be delineated from other members of the group, based on biochemical detection of a specific enzyme defect (reduced steroid sulfatase enzyme).

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Distribution

The distribution of a rash depends on factors both intrinsic and extrinsic to the body. Mechanical factors (such as trauma, environmental agents, fungal or viral infections, and drugs) are among the most common extrinsic determinants of distribution. Environmental influences, such as sunburn and light-sensitive, drug-induced reactions, may also play a major role. Psoriasis and the rare hereditary blistering disorders collectively called epidermolysis bullosa owe their distributions to local trauma; lesions that show a predilection for the elbows, knees, and lower back are common in psoriasis, and those found in the hands, feet, knees, and mouth of children are indicative of epidermolysis bullosa. A lesion of an eruption that subsequently develops where a mechanical or other physical trauma was applied is termed an isomorphic reaction. Skin diseases in which isomorphic reactions are characteristic include lupus erythematosus (sunlight), psoriasis, lichen planus, and viral warts (mechanical trauma).

Intrinsic rather than extrinsic influences explain the characteristic systematic pattern of a number of rashes. Some rashes with a symmetrical and segmental distribution may owe their pattern to the segmental arrangement of the embryo. In other rashes, it is the distribution of the cutaneous nerve supply; for example, the pattern of the rash of herpes zoster (shingles) is determined by the cutaneous distribution of the infected sensory nerve dorsal root ganglion. The blood supply to the skin has a characteristic anatomical distribution that influences the pattern of certain skin eruptions in which cutaneous vascular narrowing or blood stasis is a major feature.

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skin disease

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Diagnosis

Distribution