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Integument (Skin (Exanthems (Vesicular, Bullous, and Pustular Eruptions…

- - - - Erythema
        
        generalized phenomenon in vasodilatory states (such as scarlet fever),
        
        erythema may be followed by exfoliation, as in staphylococcal scalded skin syndrome
        
        An erythema resembling sunburn is the first skin sign of pellagra
        
        The “red neck syndrome,” also called the “red man syndrome,” may result from a too rapid infusion of vancomycin
        
        Pink disease, or acrodynia: A pink discoloration of the fingers and toes, desquamation of the palms and soles, and a morbilliform rash are dermatologic manifestations of mercury poisoning
        
        cherry red color of carboxyhemoglobinemia (vide infra) persists for some time but may be gone by the time the patient is seen
      - Cyanosis
        
        Generalized cyanosis is caused by deoxyhemoglobin, methemoglobin, or sulfhemoglobin
        
        In order to get cyanosis due to deoxyhemoglobinemia, there must be at least 5 g per dL of unsaturated hemoglobin (deoxyhemoglobin). Thus, an anemic patient with only 5 g per dL of hemoglobin cannot become cyanotic
        
        Differential cyanosis
        
        appearance of cyanosis in both lower extremities with a pink right upper extremity
        
        seen in patent ductus arteriosus when secondary pulmonary hypertension has supervened
        
        The cyanotic blood in the pulmonary artery then goes through the patent ductus arteriosus, empties into the aorta, and flows to the lower half of the body. The upper half of the body continues to get oxygenated blood from the left ventricle. If the patent ductus enters the aorta below the left subclavian artery, the left arm is pink; if it enters above the left subclavian artery, the left arm is blue. In practical terms, the appearance of the differential cyanosis finding means that it is now too late to operate on the patient.
        
        reverse differential cyanosis
        
        the arms are more cyanotic than the legs
        
        caused by transposition of the great vessels with ventricular septal defect and patent ductus arteriosus
        
        Oxygenated blood from the left ventricle can cross the ventricular septal defect into the right ventricle and the pulmonary artery, which sits just above the septal defect. When pulmonary hypertension supervenes, this oxygenated blood flows back through the patent ductus arteriosus into the descending aorta, “pinking up” the feet
        
        Livedo reticularis
        
        skin discoloration in the form of a small net
        
        usually found on the extremities
        
        The mottled or netlike reddish to blue discoloration, without discrete borders, is often more prominent after cold exposure.
        
        True Livedo reticularis
        
        might be a sign of a collagen vascular disease such as polyarteritis nodosa, dermatomyositis, rheumatoid arthritis, and systemic lupus erythematosus (and, by extension, Raynaud “disease
        
        may be seen in association with pancreatitis, shock, or bacterial endocarditis
        
        can occur with relapsing polychondritis, embolic phenomena, Parkinson disease, and certain drugs including levodopa
        
        In women, the triad of livedo reticularis, dementia (due to multiple isolated strokes), and multiple miscarriages suggests the anticardiolipin syndrome
      - Vitiligo
        
        white spots and patches on the skin
        
        begins before age 18 in half the patients
        
        Usually, the hands, feet, or face are affected first. Like a forest fire, the process of death of the pigment cells spreads and then burns out.
        
        An associated autoimmune endocrine disorder, such as thyroiditis, diabetes mellitus (Dawber, 1968), or chronic adrenocortical insufficiency, is found in about 20% to 30% of patients with vitiligo
        
        The occurrence of vitiligo with anterior uveitis (iritis), poliosis (premature graying of some or all of the hair), alopecia, and/ or dysacusia (the experience of pain caused by certain sounds) is Vogt-Koyanagi-Harada syndrome (Nordlund and Lerner, 1982). Such patients may also have posterior uveitis (chorioretinitis).
      - Fluorescence
        
        Examination under Wood's ultraviolet light
        
        golden color due to tinea versicolor
        
        coral red due to erythrasma
        
        green due to a Pseudomonas infection, especially in burns
      - Telangiectasia
        
        seen in the CREST variant of scleroderma
        
        red spots of hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease)
        
        located on the fingers, tongue, and mouth
        
        Spider telangiectasias
        
        arterial telangiectasias appearing in the region drained by the superior vena cava (the chest and upper arms).
        
        usually considered a sign of hyperestrogenism, either physiologic as in a pregnant woman or pathologic as in a cirrhotic man
        
        ataxia telangiectasia (neurocutaneous syndromes)
        
        Telangiectasia involving the ears, neck, and flexor creases at the elbows and knees (as well as the bulbar conjunctiva)
    - - Diabetic dermopathy, the most common skin sign of diabetes, starts with dull red papules that progress to form small, well circumscribed atrophic hyperpigmented patches in the pretibialarea.
      - Hyperpigmentation on the lower leg, associated with edema, dermatitis, and induration, is a feature of venous stasis and the postphlebitic syndrome
  - - - small red hemorrhage which does not blanch with pressure
      - Petechiae signify a capillary or platelet disorder, although the involvement of the capillary may be only secondary—for example, to endocarditis or fat embolism
      - In the proper clinical setting, the presence of petechiae is virtually diagnostic of fat embolism
      - the size as being pinpoint (<1 mm) upto 4mm
    - - bloody extravasation, distinguished from a petechia by its size, which is greater than 1 mm
      - generally signify large-vessel bleeding from trauma or clotting factor deficiency
      - Ecchymoses vs Mongolian spots
        
        Mongolian spots are gray-blue lesions seen in dark-skinned children, mostly over the lower back and buttocks. They are present at birth and fade over months to years. These spots have led to an erroneous diagnosis of child abuse
      - Corticosteroid therapy may cause “steroid bruising,” especially over the forearms
      - Up to 90% of scorbutic patients have petechiae and ecchymoses
    - - Scurvy should be in the differential diagnosis of any bleeding manifestations in a young child
      - A detailed dietary history is mandatory in pediatrics
      - Keep in mind that human milk contains five times more vitamin C than cow's milk
      - Scurvy must be diagnosed clinically and not by the laboratory
    - - Purple discoloration of the skin and mucous membranes resulting from intracutaneous and subcutaneous bleeding, which appears as petechiae or ecchymoses
      - As the red blood gives up its oxygen, it becomes deoxyhemoglobin, which is purple
      - The most obvious physical finding include idiopathic thrombocytopenic purpura (ITP), thrombotic thrombocytopenic purpura (TTP), Henoch-Schönlein purpura, and purpura fulminans
      - palpable purpura
        
        imply an antigen-antibody complex
      - In a febrile patient with purpuric macules, papules, or vesicles, consider bacteremia (meningococcemia, gonococcemia, staphylococcemia, and Pseudomonas infection), enterovirus infections (enterovirus cytopathic human orphan and Coxsackie), and rickettsial diseases
  - - - hives” or “nettles”) consists of itchy red or white welts of varying size and shape, usually migratory and transient
      - ask whether the patient ever had such an eruption after receiving penicillin or some other drug or after a potentially recurring exposure such as a bee sting
    - - Elevated or palpable skin lesions accompanied by scale
      - may occur with primary cutaneous disorders such as psoriasis, tinea, pityriasis rosea, lichen planus, or parapsoriasis; as a manifestation of a drug reaction; or as a sign of systemic disease such as lupus erythematosus, cutaneous T-cell lymphoma, secondary syphilis or Reiter disease
    - - Vesicles are blisters containing clear fluid. Bullae are blisters larger than 0.5 cm in diameter. Pustules are blisters that contain purulent fluid.
      - Herpes
        
        Grouped vesicles on an erythematous base are characteristic of herpetic infections, both herpes zoster and herpes simplex. Herpes Zoster involves skin in a dermatomal distribution, usually but not always unilateral. Herpes simplex also involves mucous membranes and the mucocutaneous junction
      - Impetigo
        
        Vesiculobullous lesions scattered on an erythematous base with significant golden crusting are caused by impetigo, a bacterial (staphylococcal and/or streptococcal) infection of the skin
      - Red papular pustules with white centers tend to be staphylococcal
    - - Smallpox lesions progress from macules to papules to vesicles to pustules that develop umbilications and finally to scabs
      - Vs ChickenPox
        
        In contrast with chickenpox (varicella), in which the lesions are pleiomorphic and in various stages of evolution, lesions of smallpox on one part of the body are generally in the same stage of development
        
        Lesions are more abundant on the face and extremities and involve the palms and soles in a “centrifugal” distribution, unlike the chickenpox rash. The latter is “centripetal,” largely affecting the trunk and thinning out towards the extremities.
      - typical smallpox rash begins on the face, hands, then legs, and then spreads centrally to the trunk
      - odor of smallpox is said to be quite distinctive
    - - 95% of cases are cutaneous
      - lesion begins as a small papule that progresses over a day or two to a vesicle, which may be up to 1 to 2 cm in diameter, containing serosanguinous fluid. The vesicle ruptures, leaving a necrotic ulcer
      - In the context of biological warfare, a much more lethal inhalational form is more likely. In the setting of possible exposure, a high index of suspicion is needed for patients presenting with an influenzalike illness. Patients will probably not have skin lesions
    - - Distribution is the key to the recognition of photosensitivity disorders. Both the involvement of sun-exposed areas and the noninvolvement of protected areas are important. The part of the neck shaded by the chin, hair-covered areas, recessed parts of the orbits, and the upper lip just beneath the nose, are usually spared
      - drug-induced photosensitivity
        
        Tetracyclines are by far the leading cause of drug-induced photosensitivity, followed by thiazides and the quinolone group of antibiotics
      - Differentiate from contact dermatitis
        
        An agent that has been used for years can still cause an allergic contact dermatitis. The patient changes, even if the agent does not
  - - - examining them for red color (a sign of immunologic reactivity against a “foreign” substance), white color (amelanotic sites indicating depigmentation due to tumor regression), or blue color (said to be peculiar to some melanomas but also occurring in the benign blue nevus).
      - Malignant pigmented tumors tend to be asymmetric and to have a notch
      - usually larger than a pencil eraser when first diagnosed
      - ABCD rule for diagnosing a possible melanoma is A for asymmetry, B for irregular border, C for variation in color, and D for diameter greater than 6 mm
    - - Squamous cell carcinomas
        
        Squamous cell carcinomas are also dangerous. Location in an area caudad to lines running from the angles of the mouth to the earlobes suggests this diagnosis
      - basal cell carcinomas
        
        Above that line, nonpigmented skin cancers are more likely to be basal cell carcinomas, which are less malignant in that they do not tend to metastasize
        
        locally invasive with potentially devastating consequences called a “rodent ulcer”
        
        “pearly” border—that is, a light-colored area somewhere on the edge of the tumor with the color and reflectance of pearl
        
        coupled with any vessel or telangiectasia apparent anywhere on the lesion, strongly suggest that it is a basal cell carcinoma
    - - consists of purple masses, which are sometimes scaly
      - commonly seen in association with AIDS
      - also involves mucous membranes
    - - Tumors may metastasize to the skin. The most common are Colon, Ovary (in women), Oat cell (in men), Melanoma, and Breast, supposedly in that order, forming the acronym COMB
      - B-cell tumors and T-cell tumors
        
        Of the T-cell tumors, mycosis fungoides is the best known and most pleiomorphic
      - Sézary syndrome has a characteristic cell, the Sézary cell, which is identifiable in the peripheral blood as well as the skin. Inflammation from Sézary syndrome may produce the “red man,” a white person who looks as if he has just received a large dose of histamine —another cause of the red man syndrome
    - - hyperkeratotic papule
      - easily removed with a sharp curette because they involve only the superficial layer of the skin.
      - Actinic (solar) keratosis
      - Lesions resembling seborrheic keratoses that suddenly appear and/or expand, often with pruritus, comprise the sign of Leser and Trelat . the sign has been increasingly recognized in the past decade as one of the dermatologic signals of internal malignancy. Most common are abdominal carcinomas, usually gastric adenocarcinoma, but any type of neoplasm can be involved, including leukemia or lymphoma
    - - fleshy, pedunculated tumors permit the diagnosis of neurofibromatosis (von Recklinghausen disease)
      - Before the actual appearance of the tumors, the diagnosis is suggested by the finding of at least six café au lait (“coffee with milk”) spots at least 1.5 cm in diameter
      - If you see café au lait spots, search the iris for Lisch nodules.
    - - Small groups of fleshy tumors, seeming at first glance to be acne, may be found in the nasal creases of patients
      - paranasal tumors are called adenoma sebaceum and are actually hamartomas
      - Hamartomas also afflict the heart, kidneys, and brain, with the last being responsible for the seizures
      - depigmented area in the shape of an ash leaf (best seen under a Wood's light), periungual fibromas like those seen in Sipple syndrome, shagreen (shark skin) patches, and café au lait spots (like those in neurofibromatosis) with borders
      - Of these, the ash leaf is the earliest sign to appear
  - - - Excoriations
        
        history of itching
        
        In the absence of visible skin disease, one should consider internal diseases. The most common etiologies are the secondary hyperparathyroidism of uremia, polycythemia rubra vera, lymphoma (especially Hodgkin disease), and obstructive liver disease. Lastly, itching due to the retention of bile salts may precede the appearance of jaundice.
    - - pyoderma gangrenosum
        
        more than one-third of cases of pyoderma gangrenosum occur in association with inflammatory bowel disease (ulcerative colitis or regional enteritis), and about another third occur in association with immune arthritis
  - - - Patients under 50 with hyperthyroidism have warm, moist, fine skin, likened to that of a baby
      - Patients with acromegaly have excessive sebaceous activity, resulting in a greasy or waxy feel to the skin
      - Skin thickening
        
        Crow-Fukase syndrome
        
        manifestation of chronic graft versus host disease
        
        scleroderma
      - The skin of primary hypothyroidism is coarse and dry. In contrast, hypothyroidism secondary to panhypopituitarism may be
        associated with fine skin, which may appear wrinkled like cigarette paper
    - - tested for by plucking up a fold of skin and observing whether it tents (“poor turgor”) or returns to normal (“good turgor”).
      - Poor turgor is now equated with dehydration
  - - - traditionally associated with psoriasis, lichen planus
    - - differentiate Nikolsky-positive pemphigus vulgaris from Nikolsky-negative bullous pemphigoid