A 43-year-old man comes to the clinic due to fever, night sweats, fatigue, and progressive skin lesions. The patient says the skin lesions started as small, reddish/purple papules that gradually enlarged to large nodules. He has a history of HIV and is not compliant with antiretroviral therapy or prophylactic antimicrobials. His last CD4 count 3 months ago was 50/mm³. He has been hospitalized in the past for Pneumocystis pneumonia. The patient is homeless and primarily lives outdoors but sometimes stays in shelters. Temperature is 38 C (100.4 F), blood pressure is 116/70 mm Hg, and pulse is 92/min. The patient is cachectic. White plaques are present on his palate. Hepatosplenomegaly is present. Skin examination shows several purple, pedunculated lesions on the face and extremities that are friable and bleed easily with palpation. CT scan of the abdomen reveals hypodense liver lesions that enhance with intravenous contrast. Which of the following is the most likely cause of this patient's current systemic illness?

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11ec25c8_d43f_078b_bc81_b340ccd832af_MD0003_00 Bartonella species are gram-negative, intracellular bacteria that typically establish infection through cutaneous penetration after a cat scratch (Bartonella henselae) or body/head lice bite (Bartonella quintana). The organism causes a local dermal infection, spreads to the vascular endothelium, and then attacks red blood cells. The major manifestations of infection are therefore mostly cutaneous, lymphatic, and endovascular (Cat-scratch disease, bacillary angiomatosis, endocarditis). Bacillary angiomatosis (BA) is a Bartonella infection seen primarily in patients with HIV with CD4 counts <100/mm³ (CD4-mediated immune response is crucial for control and elimination of the organism). Symptoms feature vascular cutaneous lesions that often begin as small reddish/purple papules and evolve into friable pedunculated or nodular lesions. Constitutional symptoms (eg, fever, malaise, night sweats) are typically present and organ (liver, central nervous system, bone) involvement may occur. Diagnosis is made by tissue biopsy with histopathology and microscopic identification of organisms. Treatment requires antibiotics (eg, doxycycline, erythromycin) and the initiation of antiretroviral therapy (usually 2-4 weeks later). vascular cutaneous lesions (Choice B) Candida infection is likely the cause of this patient's oral thrush (white plaques). Invasive disease is sometimes seen in patients with severe neutropenia (eg, hematologic malignancy, chemotherapy) and may manifest as multiorgan failure. This patient with HIV and angiomatous skin lesions is more likely to have BA. (Choices C and D) Cytomegalovirus (CMV) and disseminated Mycobacterium avium complex (MAC) are common infections in patients with advanced HIV (CD4 count <50/mm³). CMV may cause retinitis, colitis, pneumonitis, encephalitis, and other organ involvement. Disseminated MAC often manifests with constitutional (high fever, night sweats, fatigue, malaise, weight loss) and gastrointestinal (diarrhea, abdominal pain) symptoms. Angiomatous skin lesions are not a feature of either CMV or MAC. (Choice E) Nocardia infection manifests primarily with pulmonary and central nervous system disease, but the organism occasionally causes cutaneous infections that resemble a bacterial abscess (not angiomatous skin lesions). (Choice F) Pneumocystis jirovecii causes indolent, interstitial pneumonia in patients with advanced HIV (CD4 <200/mm³) but does not typically cause skin lesions. (Choice G) Molluscum contagiosum is caused by a pox virus and manifests as skin-colored, pearly, papular lesions, often with a dimple in the center. Systemic symptoms, vascular nodules, and liver lesions are not features of molluscum contagiosum. pearly, papular lesions Educational Objective: Bartonella henselae and Bartonella quintana can cause bacillary angiomatosis in immunocompromised individuals (eg, advanced HIV). Patients develop vascular cutaneous lesions, systemic symptoms, and sometimes organ involvement (liver, central nervous system, bone). Treatment requires antimicrobials (eg, doxycycline, erythromycin) and antiretroviral initiation.

A 43-Year-Old Man Comes to the Clinic Due to Fever