Page 239 - AIDSBK23C

Page 239

Staphylococcus may be a superimposed infection of prior eczema, scabies, herpetic ulcer,
Kaposi sarcoma, or catheter. HIV-infected patients are susceptible to staphylococcal cellulitis.
Local staphylococcal infection may be complicated by bacteremia or sepsis. Diagnosis is aided
by gram stain of pus. The culture of a biopsy specimen in cellulitis is positive in only one quarter
of patients. Risk factors include indwelling catheters, injection drug use, malnutrition,
encephalopathy, diminished antibody response, diminished B-cell mitogenic response,
immunoglobulin G subclass deficiencies, and neutrophil and macrophage
abnormalities.[973,979]

PROTOTHECOSIS.-- Cutaneous protothecosis is caused by an achlorophyllic algae of
the species Prototheca, considered mutants of the green alga genus Chlorella. Infections occur
mainly in immunocompromised individuals, including HIV infection, and are most often caused
by Prototheca wickerhamii. The incubation period may be weeks to months. At least one-half
of infectious cases are cutaneous, but deep soft tissues can be involved, leading to a chronic,
indolent infections. Cutaneous protothecosis shares similar clinical and pathologic findings with
deep tissue fungal mycoses. The typical presentation occurs most commonly on the face and
extremities as erythematous plaques, nodules, or superficial ulcers. Treatment may require a
combination of surgical excision and antifungal agents.[980]
The organisms are spherical, unicellular, nonbudding organisms from 3 to 30 mm in size.
They appear as sporangia with thick, double-layer walls filled with multiple endospores. They
reproduce asexually through internal septation and release the endospores when the parent cell
ruptures. They may be seen on biopsy and are best visualized with periodic acid–Schiff and
Gomori methenamine-silver stains. Microbiologic culture is needed for definitive diagnosis.
Biopsies may show a pandermal granulomatous inflammatory infiltrate containing lymphocytes,
neutrophils, and eosinophils. Necrosis may be observed within the granulomas; multinucleated
giant cells and plasma cells are usually present. A minimal inflammatory response may be seen
in some cases. Additional findings include hyperkeratosis and parakeratosis,
pseudoepitheliomatous epidermal hyperplasia, and lymphoid hyperplasia.

DRUG REACTIONS.-- Drug hypersensitivity eruptions or reactions commonly occur
during treatment regimens for HIV infection and related conditions. Over three-fourths of
patients with HIV infection have at least one dermatologic diagnosis made while receiving health
care, and the frequency of such diagnoses increases as HIV infection progresses. About 8% of
all dermatologic conditions seen in patients with HIV infection are drug reactions. The drugs
with the highest rate of reactions seen are trimethoprim-sulfamethoxazole (over half of patients
receiving this drug), sulfadiazine, trimethoprim-dapsone, aminopenicillins, and antituberculous
medications.[972,981]
The grossly visible lesions of drug reactions are most commonly morbilliform eruptions
of erythematous papules and macules on the trunk and extremities. Less frequently, erythema
multiforme with reddish papules and target-like lesions may occur on palms and soles. Other
infrequent patterns of involvement include Stevens-Johnson syndrome and toxic epidermal
necrolysis.[256,261,972,981]
Immune reconstitution inflammatory syndrome (IRIS) following institution of
antiretroviral therapy may lead to granuloma formation in association with either infectious or
non-infectious conditions. Non-caseating cutaneous granulomas similar to sarcoidosis may
occur. Non-infectious conditions associated with foreign body granulomatous reactions with