The diagnosis of Pneumocystis pneumonia should be considered in any immunocompromised patient with respiratory symptoms and abnormal findings on chest radiograph. Fever, dry cough, and dyspnea occur in 90% to 95% of patients, in whom radiographic evidence of bilateral perihilar and basilar infiltrates is typical. Hypoxia is frequent; pulmonary function studies show a restrictive lung defect. The most sensitive and effective method of diagnosis is to identify the organism in induced sputum or bronchoalveolar lavage fluid using immunofluorescence. If http://ebooksmedicine.net
Fig. 13.41 Pneumocystispneumonia.(A)Thealveoliarefilledwithacharacteristicfoamyacellularexudate.(B)Silverstaindemonstratescup-shapedand roundcystswithintheexudate.
treatment is initiated before widespread involvement, the outlook for recovery is good; however, because residual organisms are likely to persist, particularly in patients with AIDS, relapses are common unless the underlying immunodeficiency is corrected or prophylactic therapy is given.
Candida albicans is the most common disease-causing fungus. It is a normal inhabitant of the oral cavity, gastrointestinal tract, and vagina in many individuals. Systemic candidiasis (with associated pneumonia) is a disease restricted to immunocompromised patients that has protean manifestations.
MORPHOLOGYIntissuesections,C. albicans demonstratesyeastlikeforms(blastoconidia),pseudohyphae,andtruehyphae(
Fig.13.42A ).Pseudohyphaeareanimportantdiagnosticclueandrepresentbuddingyeastcellsjoinedendtoendatconstrictions,thussimulatingtruefungalhyphae.TheorganismsmaybevisiblewithroutineH&Estains,butavarietyofspecial“fungal”stains(Gomorimethenamine-silver,periodicacid–Schiff)commonlyareusedtobetterhighlightthepathogens.
Candidiasis can involve the mucous membranes, skin, and deep organs (invasive candidiasis). Among these varied presentations, the following merit brief mention: • Superficial infection on mucosal surfaces of the oral cavity (thrush). This is the most common presentation. Florid proliferation of the fungi creates gray-white, dirty-looking pseudomembranes composed of matted organisms and inflammatory cells and tissue debris. Deep to the surface, there is mucosal hyperemia and inflammation. Thrush is seen in newborns, debilitated patients, and children receiving oral corticosteroids for asthma, and after a course of broad-spectrum antibiotics that destroy competing normal bacterial flora. The other major risk group includes HIV-positive patients; patients with oral thrush not associated with an obvious underlying condition should be evaluated for HIV infection.
Vaginitis is extremely common in women, especially those who are diabetic or pregnant or on oral contraceptive pills.
Esophagitis is common in patients with AIDS and in those with hematolymphoid malignancies. These patients present with dysphagia (painful swallowing) and retrosternal pain; endoscopy demonstrates white plaques and pseudomembranes resembling those found on other mucosal surfaces.
Skin infection can manifest in many different forms, including infection of the nail (onychomycosis), nail folds (paronychia), hair follicles (folliculitis), moist, intertriginous skin such as armpits or webs of the fingers and toes (intertrigo), and penile skin (balanitis). Diaper rash is a cutaneous candidal infection seen in the perineum of infants, in the region of contact with wet diapers.