Dermatological Manifestations of Infectious Disease
Rash – must be considered as one facet of a disease process. Time course of the development and evolution of the rash is critical for making the correct Diagnosis. Often must wait to see what it turns into
Exanthem: A skin eruption operating as an integral part of an infectious disease
Enanthem: corresponding mucous membrane changes to an exanthem
Description of Rash:
Macule: a circumscribed discoloration of the skin, not raised above the surface of the surrounding skin. Macules often evolve into papules and many rashes are a combination of both (maculo-papular).
Papule: a small nodular elevation of the skin, commonly found in the early stages of chicken pox and smallpox.
Vesicle is a small blister containing clear or relatively clear fluid, scattered irregularly over the skin or grouped in clusters.
Pustule, a small elevation of the skin containing purulent or purulent-appearing liquefied material.
Crusts or scabs: congealed exudates on the skin, very often a late stage in the evolution of vesicular eruptions.
Wheal is a localized effusion of fluid into the skin producing a raised, white or pinkish-white area with a halo of erythema.
- Pustules formed directly as a result of local or systemic sepsis or evolve from a vesicle.
Erythema: a diffuse or localized redness of the skin,
- vary in size but never rupture.
- are characteristic of allergic rashes, being especially prominent in serum sickness.
Purpuric rashes: small hemorrhages beneath the epidermis (petechia) or larger areas of hemorrhage (ecchymosis)
- usually blanches with pressure (generally represents dilatation of capillaries and other small blood vessels).
- Intense erythema may not blanch, but lead to edema and blister formation.
- In infectious diseases, these hemorrhagic lesions often precede a more specific eruption or evolve during an exanthem.
- with intense erythema Þ pain, induration, and tenderness if deeper soft tissue structures are involved
- without intense erythema capillary dilatation may ultimately produce translocation of RBCs into the skinÞ no blanching .
Some Agents Responsible
particularly beta-hemolytic streptococcus, is capable of producing a variety of skin lesions, including:
blanching erythema associated with the toxin-mediated capillary dilatation of scarlet fever,
the tiny petechial hemorrhage (into the conjunctiva or underneath the fingernail) reflecting
an endovascular infectious focus on a heart valve (in endocarditis),
or directly infecting tissue and producing cellulitis and/or a necrotizing fasciitis
erythema marginatum – immunologically-mediated – associated with rheumatic fever – uncommon in USA today.
Staphylococcus aureus shares many versatile properties with the streptococcus, but has many unique mechanisms.
Some Dermatological Manifestations of Infectious Disease
Impetigo: initially vesicular, later crusted, superficial dermal infection
Furuncle: a deep inflammatory nodule, usually developing from a preceding folliculitis, a pyoderma located within hair follicles, in apocrine regions
- group A streptococci is usual agent and is usually seen in children.
- Staphylococcus aureus is increasingly involved, either alone or in combination with a group A streptococcus.
- Histopathology: a superficial, intraepidermal, vesiculopustular lesion.
- Gram stain of these vesicles show gram (+) cocci in chains or clusters, depending on predominant organism.
- The lesions remain superficial and do not ulcerate or infiltrate the dermis
- mild regional lymphadenopathy is common. Healing occurs without scarring, the lesions are painless
- constitutional manifestations are surprisingly minimal.
Carbuncle: a more extensive process extending into the subcutaneous fat in areas covered by thick, inelastic skin
- usually due to Staph. aureus, although Pseudomonas aeruginosa can be acquired from swimming pools and whirlpools
Ecthyma: resemble impetigo initially but are capable of penetrating through the epidermis.
- multiple abscesses develop, separated by connective tissue septae which drain to the surface along hair follicles;
- Staph. aureus is almost invariably the etiologic agent.
Chancriform: lesions caused by a large group of locally invasive infectious agents
- Group A streptococci either produce these lesions de novo or secondarily infect pre-existing superficial lesions (insect bites, scratches, etc.) resulting in the same clinical picture.
- The same picture may be reproduced in the course of Pseudomonas bacteremia in neutropenic patients.
Erysipelas: a distinctive type of superficial cellulitis of the skin with prominent lymphatic involvement
- produce a punched out, necrotizing and destructive lesion (anthrax is one of the most prominent)
- (N.B. The chancre of syphilis is not a necrotizing lesion; it is painless and heals without scarring!).
Cellulitis: an acute spreading infection of the skin, which involve the subcutaneous tissues
- almost always due to group A streptococcus, rarely to S. aureus.
- Caused by exotoxin, affects middle aged patients in warm climate, often starts with erythematous cutaneous rash on face
Infectious gangrene: an often rapidly developing cellulitis with extensive necrosis of subcutaneous tissues and overlying skin.
- extends deeper than erysipelas
- group A streptococcus or S. aureus is most frequently the etiologic agent.
- usually occurs in areas of previous trauma, but can result from hemotogenous spread to skin and subcutaneous tissues.
Lymphadenitis: acute or chronic inflammation of lymph nodes, restricted to a solitary node or regional lymphadenitis.
- clinical picture: depends on specific causative organism, the anatomic location of infection and predisposing conditions.
- (1) necrotizing fasciitis (streptococcal gangrene)
- (2) gas gangrene (clostridial myonecrosis) and anaerobic cellulitis
- (3) progressive bacterial synergistic gangrene
- (4) synergistic necrotizing cellulitis (perineal phlegmon and gangrenous balanitis).
- Pathologic changes of gangrenous cellulitis:
- necrosis and some hemorrhage into the skin and subcutaneous tissues
- abundant PMNs (although in clostridial myonecrosis: exudate is thin and consists of fluid, fibrin and gas but few WBCs)
- fibrin thrombi present in small arteries and veins of the skin and subcutaneous fat, particularly streptococcal gangrene
- Crepitant cellulitis characterized by the presence of bubbles of gas within the soft tissue; readily obvious on x-ray.
- usually indicates the presence of anaerobic bacteria, alone or in combination with other organisms
- is an indication for immediate surgical debridement and removal of obviously infected tissue.
- The diabetic foot is particularly prone to polymicrobic infection because of vascular and neuropathic changes
- Fournier's gangrene: serious form of necrotizing fasciitis occurring around male genitals, involving 1 or more:
- perineum, penis, scrotum, lower abdominal wall
- risk factors: DM, local trauma, periurethral extravasation of urine, perirectal or perianal infections, prior surgery
Lymphangitis: an inflammation of lymphatic channels, usually in the subcutaneous tissues.
- Lymphadenopathy may be generalized during a systemic infection.
- Microscopy: non-suppurative, suppurative, granulomatous, or caseous, depending on the nature of the bug.
- May or may not progress to abscess formation.
- Acute lymphadenitis is associated with pain, erythema and acute lymphedema.
- Chronic lymphadenitis has non-specific histology with proliferative hyperplasia of RE cells, and prominent germinal centers in dilated lymph sinuses filled with mononuclear cells. Also seen in patients with a lymphoproliferative disorder.
- either as an acute process of bacterial origin or as a chronic most commonly due to group A streptococci in USA
- or subacute process of mycotic, mycobacterial, or filarial etiology.
- usually caused by Sporotrichum schenckii, although other agents can produce similar lesions, including various mycobacteria, Nocardia species, and, occasionally, Staph. aureus (botryomycosis).
- In the legs, thrombophlebitis may produce linear areas of tender erythema, usually without tender regional adenopathy,
- distinguishes it from lymphadanitis.
- Filariasis is a consideration when an appropriate geographic history is obtained.
- Sporotrichosis is considered when chronic ulcerative lymphangitis develops in patient working with plants, soil or timber.
- Mycobacterium marinum is suggested etiologically when "sporotrichoid" lesions develop in a person who has been around swimming pools and fish tanks.