The human body is an organic whole, and the systems, organs, and tissues are closely interrelated. Skin diseases are often the skin manifestations of diseases of various systems. This section introduces the skin manifestations of common system diseases as follows: I. Skin manifestations of digestive system diseases The digestive system is the only organ of the body that draws nutrients from food, digestive dysfunction, poor digestion and absorption of nutrients, nutrients in short supply, insufficient energy, and failure to maintain normal life activities of the body, each system will undergo different pathophysiological changes, causing disease. The skin is no exception, the common skin manifestations of digestive system diseases are introduced as follows: (1), malnutrition: can be caused by digestive system diseases caused by digestion and absorption disorders, nutrient supply and the increase in body needs caused by the lack of protein, vitamins and trace elements caused by skin lesions. Protein deficiency skin can show special waxy erythema, dry skin, peeling, sometimes the skin will appear large blisters, ulceration to form superficial ulcers, individual deep ulcers and gangrene, dry hair, loss of luster, can be sparse or extensive loss, nail softening, thinning. Mucous membrane damage is common in stomatitis, mouth ulcers, etc. Vitamin deficiency: deficiency of vitamin A, manifest dry skin, extremities as follicular keratotic papules, accompanied by night blindness. Riboflavin deficiency often manifests as keratitis, lipitis, tongue inflammation and scrotum inflammation. Vitamin B12 deficiency can lead to pernicious anemia and neurological damage. Two-thirds of pernicious anemias have tongue lesions with inflammatory blisters and superficial ulcers that are painful to the touch. Neuropathy shows finger joint ulcers, skin bleeding, sweating dysfunction, nail dystrophy and other manifestations. Vitamin PP deficiency disease, the skin manifests as erythema, roughness, flaking, pigmentation, etc. in the exposed parts of the extremities. Vitamin C deficiency disease manifests as dry skin, similar to vitamin A deficiency disease occurs on the extremities of the hair follicle mouth enlargement and keratinization, hair follicles with curly hairs inside. The gums are swollen and red, prone to erosion, necrosis and bleeding. The skin is prone to flaky petechiae or petechiae on pressure or impact, and in severe cases, bloody blisters may occur, which form ulcers after breaking. There is also nosebleeding, blood in urine, blood in stool, pericardial and thoracic bleeding, and occasionally intracranial bleeding. With the improvement of economic living standard, some nutritional deficiency diseases are rare. But secondary malnutrition due to other diseases and drugs are sometimes seen. (2) Gastrointestinal bleeding and its accompanying skin disease: Gastrointestinal bleeding is an important problem in internal medicine, and sometimes the etiology is very difficult to diagnose. Cutaneous manifestations may provide clues to confirm the diagnosis of GI bleeding. (1) Hereditary hemorrhagic capillary dilation: This disease is autosomal dominant and is characterized by abnormal dilation of small blood vessels in the skin, mucous membranes and internal organs with bleeding. The bleeding sites are mostly in the gastrointestinal tract and mucous membranes, but can also occur in the urinary tract, respiratory system, and nervous system. The typical lesions are clusters of tiny capillary plexuses, purplish or bright red dots, above the skin surface, which may be spider-like, thread-like or branched, on the face, ears, forearms and nail beds. Some of the skin is prone to petechiae, but can fade. (2) Malignant atrophic papulosis: The rash occurs mainly on the trunk, in batches, starting as a pale rose-colored, round, edematous papule, the damage expands, the center is umbilical fossa-like, porcelain white, surrounded by bruising, and capillary dilatation, and finally atrophy occurs. Infarction of the intestine may be associated with severe abdominal pain, blood in the stool, and diffuse peritonitis due to multiple intestinal perforations. (3) elastic pseudo-yellow warts: skin lesions characterized by initial occurrence in the neck, axilla, groin, abdominal wall, etc., the skin fine lines thickened, yellow, continue to develop as yellow plaques, leather-like or cobblestone-like, later dermal elastic fibers degeneration, the skin appears relaxed folds. The disease is often associated with gastrointestinal symptoms, of which gastrointestinal bleeding is the most serious. Gastrointestinal bleeding occurs in about 14% of patients at various times. (4) Allergic purpura: The skin is a sudden pinpoint or soy-sized petechiae or petechiae, which can be accompanied by edematous erythema, wind masses, and occasionally small blisters. 75% of patients have symptoms of abdominal pain of varying degrees. The most common is abdominal pain with loss of appetite, nausea, vomiting, vomiting of blood, blood in the stool, blood in the urine, and diarrhea. Severe intestinal bleeding can lead to intestinal perforation or intestinal paralysis and intussusception. Bleeding can also occur in other parts of the body, but it is rare. (3), Liver disease: The skin can be a mirror of liver disease and respond sensitively to liver disease: (1) Skin color change: If the skin color becomes gray and lusterless with hyperpigmentation, it is mostly seen in cirrhosis. Yellowing of the skin and yellowing of the sclera are seen in obstructive jaundice and hepatocellular necrosis in hepatitis. (2) Vascular abnormalities: spider nevus, capillary dilation, abdominal wall varicose veins, calf ulcers, and palmar erythema are seen on the skin, but are caused by cirrhosis. Cirrhosis may also have coagulation disorders and purpura and subcutaneous bleeding. (3) Hair changes: Due to the elevated estrogen levels and decreased androgen levels caused by liver disease, resulting in secondary changes in hair, thinning, thinning hair, male beard, axillary hair, pubic hair reduction. (4) Nail changes: due to liver disease caused by a decrease in plasma protein, nail bed edema, nail plate becomes cloudy, produce white nail, nail half moon disappears, nail becomes brittle. (5) Skin itching: due to liver dysfunction its metabolites accumulate in the body, or bile salts on the skin sensory nerve endings stimulation caused by different degrees of itching of the skin, can be paroxysmal or persistent, can be systemic or limited. (4), the skin manifestations of pancreatic diseases (1) nodular fat necrosis: the onset of pancreatic diseases (acute, chronic or hemorrhagic pancreatitis, pancreatic cancer, pancreatic epithelial tumors, etc.), may be increased secretion of pancreatic protease or low levels of a-antitrypsin in the blood, while the role of lipase, fat necrosis, in the skin is manifested by the formation of nodules in the subcutaneous fat layer, straight through 1 – 3 cm in size. -3 cm in size, soft and fluctuating, flushed and edematous, painless or painful, usually on the extensor side of the calf, occasionally on the buttocks, upper limbs and trunk. (2) Necrolytic loosening wandering erythema: skin damage starts as infiltrative erythema, ring-shaped or irregular-shaped, later on the basis of erythema occurs flaccid blisters or blisters, blisters quickly rupture, there is desquamation or crusting, erythema continues to expand, the center has self-healing, sometimes there is pigmentation, edge desquamation. The lesions often alternate in severity and recurrence. This disease is mostly seen in glucagonoma or islet cell carcinoma. However, it has been seen in chronic pancreatitis. It has been reported that the lesions disappear quickly after tumor removal. In addition to the above, pancreatic disease can also cause urticaria, reticulocutaneous cyanosis, yellow tumor, migratory thrombophlebitis, etc. The human body is a unified whole, and each system is interrelated and affects each other. Each system’s disease can affect other systems, and respiratory system diseases can affect the skin, or both or several systems can be involved at the same time. The performance of common respiratory diseases is described as follows: (1), tuberculosis: the same mycobacterium tuberculosis infection, due to the site of infection, the body’s immune status is different, the body will make different responses. Tuberculosis also has a variety of clinical manifestations, primary tuberculosis, skin-related diseases often occur in nodular erythema, hard erythema, common lupus, scrofulous moss and papular necrotizing tuberculosis rash, etc.. (2), deep pulmonary fungal infection: deep fungal cause skin changes are mostly reactive lesions, is a reaction to the toxins of the fungus, the products of decomposition of tissue. Pulmonary budding fungal disease common nodular erythema; histoplasma infection early occurrence of polymorphic erythema; coccidioidomycosis 3-7 weeks after the onset of polymorphic erythema and nodular erythema; cryptococcosis, Candida albicans can also have skin damage, a variety of forms. (3), malignant granulomatosis or Wegener’s granulomatosis: is a necrotizing granulomatous vasculitis of the respiratory tract, is a rare but serious disease. 40-50% of patients have skin manifestations, also for the skin of necrotizing vasculitis manifestations. Once the skin is involved the prognosis is poor. (4), lymphomatoid granulomatosis: mainly invades the lungs, skin and nervous system. The lung manifestations are cough, chest pain, dyspnea and hemoptysis. The skin manifests with erythema, plaques and skin nodules, which are more common in the extremities. It is a pathological change of lymphatic reticulo-granulomatous vasculitis. (5), Nodular disease: It is a disease of unknown cause, invading multiple organs. It often invades the lungs and presents with large, punctate, striated or lamellar, dense shade shadows on both sides of the lungs and enlarged hilar lymph nodes or extensive pulmonary fibrosis. Symptoms include cough, shortness of breath, chest pain and coughing sputum. The skin lesions are polymorphic, with papules, patches, and nodules. The lesions are multifocal, soft or hard, light red or purplish red, with dilated capillaries or covered with scales. (6), connective tissue disease: in systemic lupus erythematosus, dermatomyositis, scleroderma, etc. can have lung interstitial pneumonia, pulmonary fibrosis, pleurisy, emphysema, lung prone to recurrent infections. It often shows chest pain, cough, hemoptysis, dyspnea, etc. The endocrine system mainly includes the pineal gland, hypothalamus, pituitary gland, thyroid gland, parathyroid gland, adrenal gland, gonads, pancreas, thymus, etc. The endocrine system is regulated by the hormones it secretes. The hormones secreted by the endocrine system regulate the growth and development of the human body, reproduction, metabolism of sugar, protein, fat, electrolytes and trace elements, as well as the body’s response to external environmental stimuli. The skin is no exception, and the common endocrine system diseases causing skin changes are introduced as follows: 1. Pituitary gland diseases (1) Pituitary hyperfunction: excessive secretion of growth hormone triggers acromegaly, in addition to hypertrophy and hyperplasia of limb bones and soft tissues, the skin shows hypertrophy, edema-like, protrusion of the lower lip, and a huge tongue. In addition to the hypertrophy of the bones and soft tissues of the extremities, the skin exhibits hypertrophy, edema, protrusion of the lower lip, and a large tongue. Skin discoloration, hyperfunction of sweat and sebaceous glands, excessive sweating, oiliness, and acne can occur in 40% of people. Hair increases, pores become prominent, nails flatten, broaden, grow fast, and nail half-moons disappear. The nail plate may develop longitudinal lines and cracking. A small number of people may develop acanthosis nigricans. (2) Hypopituitarism: the skin is pale, not easily tanned, the skin is prone to hypopigmentation, the skin and subcutaneous tissues are thinner, the eyes and mouth are prone to wrinkles, showing signs of premature aging. Hair is sparse, and axillary hair, pubic hair and beard are also reduced. The sweat and sebaceous glands decrease in function and secretion, and the skin becomes dry, rough and scaly. The nail plate becomes thin, brittle, cloudy, may occur nail longitudinal ridge and nail peeling. 2, adrenal gland disease adrenal gland function is regulated by the hypothalamus and pituitary secretion of adrenocorticotropin-releasing hormone and adrenocorticotropic hormone, etc., may occur hyperfunction or hypofunction. (1) Hyperadrenal function: Common skin changes include thinning of the skin, exposure of blood vessels, increased vascular fragility, and susceptibility to purpura damage. The subcutaneous fat distribution is abnormal, and full moon face and buffalo back signs occur. Facial hair thickens, becomes longer, and deepens in color. In some cases, extensive and severe hirsutism occurs, or male pattern baldness occurs. Increased secretion of sweat glands and sebaceous glands, hyperkeratosis of pores, and secondary acne. The skin is susceptible to superficial fungal infections, mostly seen in lichen planus and lichen erythematosus. (2) Hypoadrenalism: The most common skin changes are hyperpigmentation of the skin mucosa, generalized diffuse deepening of pigmentation, but more pronounced in exposed areas such as the face, extremities, nipples, areolas, external genitalia, waist and hip folds, lower abdominal midline, nail roots, and scars. The pigmentation is as dark as carbon and as light as brown-black, brown-yellow, or bronze. Uneven pigmentation on the face. The forehead, around the eyes are deeper, cheeks, lips, gums and palate mucous membrane have varying sizes of dots or patches of pigmentation. 3. Thyroid disorders The secretion of the thyroid gland is regulated by the hypothalamus and pituitary thyrotropin-releasing hormone and thyrotropin. (1) Hyperthyroidism (hyperthyroidism): People suffering from hyperthyroidism have flushed face with palmar erythema, head and neck may be temporarily congested, blood vessels expand and blood flow increases, and skin temperature rises. The skin is moist due to increased sweat production. The skin may be diffusely pigmented and patchy, but the mucous membranes are not involved. Vitiligo is also present in 5-10% of patients with hyperthyroidism. Hair becomes fine and soft, and diffuse alopecia or baldness may occur, and hair turns prematurely white. Fingernails grow rapidly and often suffer from nail stripping. (2) Hypothyroidism: symptoms are opposite to hyperthyroidism, due to reduced sweat and sebum secretion, dry and flaky skin, ichthyosis-like appearance, pore keratinization, keratin formation, and itching of the skin may occur. Due to reduced metabolism, vasoconstriction and reduced blood flow, the skin is pale and the skin temperature is reduced. There is a large amount of mucopolysaccharide deposition around the dermis and blood vessels, and mucinous edema and purpura damage occurs in the skin. Hair is sparse, growth is slow, nails become thin and brittle, and growth is slow. 4. Pancreatic diseases (1) Glucagonoma: the secretion of glucagon by pancreatic islet a-cell tumor causes wandering erythema, and the lesions are widespread all over the body, mostly in the lower abdomen, groin, perineum, thighs, and around the mouth and nose. Initially, the lesions are light erythematous spots, papules and papules of different sizes, which become dark purple-red within 1-2 days, with blisters or pustules in the center, forming vesicles and crusts after rupture, and later flaking and healing, leaving light brown or bronze pigmentation. New rashes may appear continuously, fusing with each other to form a gyrus or multi-ring shape. The rash expands and heals in a polymorphic fashion. The rash may also be accompanied by keratitis, linguitis, conjunctivitis, and vaginitis. (2) Diabetes mellitus About 30% of diabetic patients have skin damage, and the lesions are diverse. Atrophy of the skin occurs due to vascular abnormalities, hair loss, cold toes, nail dystrophy, gangrene of the feet, or erythema like dermatitis. The skin often develops secondary bacterial and fungal infections, folliculitis, boils, carbuncles, dermatophytosis, candidiasis, epidermolysis bullosa, trichophytosis, etc. Special skin manifestations include diabetic lipoid progressive necrosis, diabetic sclerosis, disseminated annular granuloma, diabetic maculopathy, diabetic rash xanthoma, diabetic pruritus, etc. 5, gonadal diseases Hyper gonadal function: 1), excessive androgens, rough skin, thickening, enlarged facial pores, oily skin with acne. Extremities, chest and beard hair increase and thicken. Perineum, external genitalia. Increased skin pigmentation in the areola and armpit. 2) Excessive estrogen, excessive growth of female pubic hair. Feminization of male breast, some may occur chloasma, capillary dilation, or spider nevus. Candida vaginitis, pregnancy herpes, etc. are also common. Hypogonadism: 1), androgen reduction, testicular insufficiency occurs before sexual maturity, thin and tender skin, hypopigmentation and pale. The sebaceous glands and sweat glands do not develop, the skin is not greasy, acne does not occur, hair follicles do not develop, showing beard, axillary hair, pubic hair is absent. After sexual maturity, androgen reduction occurs, the skin becomes fine and non-greasy, and hair can continue to exist although it is reduced. 2), estrogen reduction – menopause syndrome: After menopause, the skin has recurrent episodes of flushing, lasting 2-5 minutes, sometimes up to 15 minutes, which can be extended from the face to the whole body, and can be accompanied by a lot of sweating, etc. Skin manifestations of blood system diseases The human body relies on blood for metabolism to maintain life activities, and diseases of the blood system will definitely affect other systems, and the skin will not be an exception. The common skin manifestations of traditional blood diseases are: 1. Anemia: There are several types of anemia, such as iron deficiency anemia, giant cell anemia, aplastic anemia, hemolytic anemia, etc., but laboratory tests are needed to distinguish them. The basic manifestations of the skin in anemic patients are: pale skin, dry hair, baldness, skin pigmentation, inflammatory changes in mucous membranes (linguitis, labyrinthitis, ulcers) and nail dystrophy changes, often combined with secondary infections such as candidiasis, impetigo, etc. (1) Iron deficiency anemia: skin changes are common in labyrinthitis, linguitis, anthelmintic, baldness, itchy skin and combined with Candida infection. (2) Macrocytic anemia: The main skin manifestation is vitiligo, which is 10 times higher than normal controls. Alopecia areata, alopecia areata and linguitis are also seen. Rarely seen are herpes-like dermatitis, aspergillosis, etc. (3) Aplastic anemia: Most patients have limited or widespread skin pigmentation in a reticular pattern, most obvious in the neck and flexors of the extremities, and the lower part of the trunk. Mucosal leukoplakia, traumatic macules, and purpura are also common. Secondary skin infections are associated with allodynia. (4) Hemolytic anemia: The most important skin manifestation is skin ulceration, which mostly occurs in the lower 1/3 of the calf, and in half of the patients both calves occur at the same time, and unilateral occurrence is more common in the left calf. The ulcers are straight through 1-10 cm, with distinct margins and occasionally multiple ulcers that heal slowly with residual atrophic scars. There can also be jaundice, itchy skin, baldness and other changes. 2. Methemoglobinemia and sulfhemoglobinemia: The skin manifestation is the same as cyanosis, most obvious on the lips and nail bed. 3. True erythrocytosis: The skin and mucous membranes show purple and cyanosis of the cheeks, lips, nasal tip, ears, neck and distal extremities, the oral mucosa and tongue are dark red, the conjunctiva is congested, some can be complicated by rhinorrhea, gingival, gastrointestinal and genitourinary tract bleeding, skin petechiae, and rarely erythema extremities and generalized itchy skin. 4. Leukocytosis: It can be seen in erysipelas, pustular psoriasis, erythema multiforme, febrile neutrophilic dermatosis, certain drug rashes, etc. 5. Eosinophilia: seen in allergic diseases, herpetic diseases, connective tissue diseases, eosinophilic fasciitis, vasculitis and certain tumors, such as Hodgkin’s disease, mycosis fungoides, etc. 6. Leukocyte abnormalities – leukemia: The skin manifestations of leukemia are called cutaneous leukemia. The rash can be divided into two categories: atopic and non-atopic. Atopic lesions are caused by leukocyte infiltration and may show papules, nodules, plaques or erythroderma, spreading over the entire body skin. Non-specific lesions are not infiltrated by leukemic cells and may take the form of macules, papules, blisters, pemphigus, purpura, nodules, and ulcers. Pruritus is intense. 7, microangiopathy and coagulation dysfunction: purpura is a common skin manifestation, which is a general term for blood leaking out of blood vessels and bleeding under the skin, submucosa. It can be generally divided into microangiopathy and coagulation dysfunction. Those with damaged blood vessel wall include allergic purpura, depressed purpura, vitamin deficiency purpura, toxic purpura, senile purpura, steroidal purpura, etc. Infectious purpura has vasculitis, which can also be platelet-based or coagulation-deficient. Coagulation disorders, which can be caused by a variety of causes of thrombocytopenia, abnormalities. The purpura caused by thrombin, disorders of thrombin production, anticoagulant drugs, etc. are in this category. V. Skin manifestations of circulatory system diseases How does microcirculatory disorders occur: Under normal circumstances, the microcirculatory blood flow is adapted to the metabolic level of human tissues and organs, so that the physiological functions of the organs in the body can operate normally. The capillaries of human body are extremely thin and long, in which the blood flow rate is extremely slow, only 0.41 mm per second. In such long blood vessels, once there are impurities turbid in the blood, such as fat particles, cholesterol, alcohol, nicotine, drug residues, chemical residues, etc., they will not only block the blood vessels, but also make the vessel walls thicken, the lumen is thinner, resulting in poor blood flow within the microcirculation. Once the body’s microcirculation is impaired, the tissue system or internal organs it feeds will: not get oxygen and nutrition, waste cannot be effectively discharged, and the living environment is poor, thus unable to perform normal functions, resulting in degeneration of body functions in light cases, and leading to the occurrence of diseases in serious cases. Liu HeLiang, Department of Urology, Xijing Hospital, has reduced microvessels in the skin as we age, and the blood supply and oxygen supply are inadequate, resulting in reduced skin nutrition, decreased skin elasticity, sagging and wrinkles, chloasma, age spots, premature crow’s feet around the eyes, eye bags, etc.