Skin ulcer and pyoderma

Figure 20.1 Algorithm for the evaluation of leg ulcers. ABI, ankle/brachial index; DDx, differential diagnosis; CBC, complete blood count; ESR, erythrocyte sedimentation rate; AFB, acid-fast bacilli.

A history of unusual occupation, hobby, or exposure can suggest causes of skin ulcers such as tularemia in rabbit hunters, Mycobacterium marinum in aquarium enthusiasts, and leishmaniasis in travelers to endemic areas of the Middle East, North Africa, and Central and South America. Host factors also may predispose individuals to any of several types of ulcers. Patients with malignancies can be at risk for ecthyma gangrenosum caused by Pseudomonas aeruginosa, or dense neutrophilic infiltration of the dermis that is noninfectious but responds to steroids (Sweet’s syndrome, discussed later). Ecthyma gangrenosum caused by P. aeruginosa is a rapidly progressive (12 to 24 hours), necrotic ulceration with hemorrhagic bullae and skin sloughing in the setting of gram-negative sepsis and neutropenia. Empiric agents for ecthyma gangrenosum should include tobramycin plus piperacillin, ceftazidime, or imipenem.

Treatment of skin ulcers depends on the cause of the lesion. For venous stasis ulcers, local care with occlusive dressings on the wounds and compression bandages to aid venous return is necessary. If cellulitis or folliculitis is present, antibiotics to cover Staphylococcus aureus (including methicillin-resistant S. aureus [MRSA]), streptococci, and gram-negatives should be administered empirically pending cultures. After the ulcer has healed, compression stockings should be worn to prevent new ulcers. Therapy for other types of ulcers should address their cause; Table 20.1 outlines the clinical presentation and epidemiology of infectious ulcers.

Table 20.1 Clinical presentation of skin ulcers caused by infectious agents

Cause	Laboratory workup	Epidemiology	Clinical clues to diagnosis
Bacterial	Routine culture and Gram stain
Bacillus anthracis (anthrax)	Gram (+) rod, biopsy for immunohistochemistry and PCR	Wool handler; Western Asia, West Africa, Eastern Europe; injection drug users (heroin); potential bioweapon	Lesions on face and arms; painless papule develops into vesicle that dries, forming black eschar that then separates from the base to form an ulcer with marked surrounding gelatinous edema; LN common; injectional anthrax – higher mortality and shock, significant edema
Corynebacterium diphtheriae (diphtheria)	Gram (+) rod	Tropical climates; rare in the United States	Ulcer with sharp margins and clean base; pre-existing skin lesions may become infected
Francisella tularensis (tularemia)	Gram (–) coccobacillus, serology	Rabbits, muskrats, beavers; North America, Japan, Europe, former Soviet Union; potential bioweapon	Systemic febrile illness; tender ulcer with painful LN
Nocardia spp.	Branching, beaded gram (+) rod, modified AFB (+)	Immunocompromised patients, soil exposure	Ulcer with purulent drainage, nodular lymphangitis
Pseudomonas aeruginosa (ecthyma gangrenosum)	Gram (–) rod, may have associated bacteremia	Neutropenic or immunocompromised patients	Rapidly progressive eruption from papules to hemorrhagic vesicles or bullae that undergo central necrosis and ulceration
Polymicrobial	Mixed gram (+), gram (–), and anaerobes	Debilitated, immunocompromised, diabetic patients	Pressure sores, decubitus ulcers, foot ulcers
Yersinia pestis (plague)	Gram (–) coccobacillus, bipolar-staining “safety pin” morphology, serology	Rodent zoonosis transmitted to humans via fleas; Far East, India, Africa, Central and South America, potential bioweapon	Bubonic plague with classic inguinal painful LN; may have skin lesions on lower extremities; pustule, papule, vesicle, or eschar may occur at inoculation site
Spirochetes
Treponema pallidum (syphilis)	Serology	Sexually transmitted disease	Tertiary syphilis; nodular, ulceronodular, gummas; punched-out ulcer with gummy discharge
Fungal	Fungal smear, culture
Aspergillus spp.	Septate hyphae; serum galactomannan assay in high risk patients	Immunocompromised, HIV positive	Ulcers, plaques, nodules, pustules; may be associated with trauma, intravenous catheter sites, secondary colonization of existing wounds, or direct extension from lung to chest wall
Blastomyces dermatitidis	Broad-based budding yeast, dimorphic fungus	Sugar cane worker, HIV positive, immunocompromised; North America, Africa	Subcutaneous nodule that enlarges and ulcerates, forming a crusted, verrucous plaque; may resemble squamous cell carcinoma
Coccidioides immitis	Dimorphic fungus, serology	Soil exposure, HIV positive; Southwestern United States, Northern Mexico, Central and South America	Usually single nodule or plaque; may form pustules, subcutaneous nodules, or abscesses
Cryptococcus neoformans	India ink, encapsulated yeast, mucicarmine (+) capsule, cryptococcal antigen (serum and CSF)	Exposure to pigeons, soil exposure, HIV positive, immunocompromised	Papule with crust resembling molluscum contagiosum; also forms ulcers on skin, mouth, and genitalia; may have lung or CNS involvement
Histoplasma capsulatum	Dimorphic fungus, histoplasma antigen (urine and serum)	Bats, birds, and soil exposure; HIV positive, immunocompromised; Eastern and Central United States in Ohio/Mississippi river valleys, Central and South America, West Indies, Africa, Madagascar	Papule with crust resembling molluscum contagiosum; ulcerative plaques and oral ulcerations
Sporothrix schenckii	Dimorphic fungus	Rose gardening, soil exposure	Papule or pustule at inoculation site develops into subcutaneous nodules or ragged-edged ulcer with proximal nodular lymphangitis; usually on upper extremities
Mycobacterial	AFB smear, culture
Mycobacterium marinum	AFB (+), growth at 30–32°C	Water, aquarium enthusiasts	Ulcer with thin seropurulent drainage, nodular lymphangitis
Mycobacterium ulcerans (Buruli ulcer)	AFB (+), PCR for the insertion sequence IS2404 and IS2606 in swabs or tissue samples	Africa, Australia, South East Asia, South America, North America (Mexico); 2- to 3-month incubation period, usually associated with trauma	Subcutaneous nodule that ulcerates with extensive scarring and contracture formation; edematous lesion rapidly progresses to extensive ulceration, may have osteomyelitis contiguous to ulcer
Mycobacterium avium complex	AFB (+)	HIV positive, immunocompromised; soil, water	Multiple subcutaneous nodules or ulcers; may be associated with cervical lymphadenitis drainage to skin, or direct inoculation
Mycobacterium haemophilum	AFB (+), requires iron-supplemented culture medium and incubation at 30–32°C	Australia, United States, Canada, France, Germany, Singapore; HIV positive, transplantation	Papules develop into pustules which form deep ulcers, usually on extremities overlying joints; may have septic arthritis +/– osteomyelitis, may have LN
Mycobacterium tuberculosis	AFB (+), PPD or interferon-γ release assay helpful if positive	Worldwide	Nodules or ulcers especially in HIV-positive patients, scrofuloderma, plaques
Viral
Herpes simplex	DFA, viral culture	Sexually transmitted disease	Oral, perineal, genital ulcers; whitlow on hands; lesions with thin-walled vesicles; shallow painful ulcers
Parasitic
Leishmaniasis	Punch biopsy, aspirates, or scrapings of skin for culture, histopathology and touch prep using Wright’s and Giemsa stains looking for amastigotes at base of lesion; serology; PCR of tissue aspirates or peripheral blood	Sandfly bites, travel to endemic area (military or civilian); incubation period weeks to months	Papule at the site of insect bite enlarges to form a nodule, which then develops into a punched-out ulcer; may have associated LN; rarely nodules form without ulceration; may involve nasal or oral mucosa
Old World L. major L. tropica L. (L.) aethiopica		Mediterranean, Middle East, Africa, Southern Asia, India
New World L. mexicana complex Viannia subgenus: L. (V.) braziliensis L. (V.) panamensis L. (V.) guanensis L. (V.) peruviana		Latin America, Central and South America

Abbreviations: LN = lymphadenopathy; Gram (+) = gram-positive; Gram (–) = gram-negative; AFB = acid-fast bacilli; CNS = central nervous system; DFA = direct fluorescent antibodies; PCR = polymerase chain reaction; PPD = purified protein derivative; CSF = cerebrospinal fluid.

Noninfectious ulcers

Noninfectious causes of cutaneous ulcers include drug reactions, collagen vascular diseases, and malignancy. Drugs reported to cause ulcerations include methotrexate, etretinate, and warfarin. Wegener’s granulomatosis, a systemic disease with involvement of the respiratory tract and kidneys, can form necrotizing ulcerations of the skin.

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