Carrión's disease — DTM&H MCQ

Correct answer: E — Bartonella bacilliformis

The correct answer is E, Bartonella bacilliformis. This organism causes Carrion's disease, a biphasic Andean bartonellosis in which an acute haemolytic febrile illness (Oroya fever) is followed weeks to months later by a chronic cutaneous eruptive phase, verruga peruana, exactly as described in this returning traveller from Peru. The organism invades erythrocytes in the acute phase, explaining haemolysis and a negative culture once bacteraemia has cleared, and then infects vascular endothelial cells in the chronic phase, producing angiogenic red-purple papulonodular lesions. Transmission is by Lutzomyia sandflies in Andean valleys, and the geographic clue (Peru) together with the sequential Oroya fever to verruga peruana pattern is pathognomonic for this pathogen. Why the other options are wrong: C. Bartonella henselae: this causes cat-scratch disease and bacillary angiomatosis, transmitted by cats and fleas, not by sandflies, and does not produce the Oroya fever to verruga peruana sequence. B. Bartonella quintana: causes trench fever, transmitted by the human body louse, associated with lymphadenopathy and relapsing fever rather than verrucous skin lesions or the biphasic Andean disease pattern. D. Rickettsia prowazemii: causes epidemic typhus via body lice, presenting with fever, headache and a maculopapular rash, not verrucous nodules, and has no link to Peru's Andean sandfly ecology. A. Treponema carateum: causes pinta, an endemic treponematosis with hyperpigmented or achromic skin patches, not preceded by a haemolytic febrile illness, and unrelated to sandfly transmission. Key point: geographic exposure in the Andes plus the sequential pattern of haemolytic Oroya fever followed by verrucous verruga peruana lesions is diagnostic of Bartonella bacilliformis (Carrion's disease).

Reference: DermNet NZ, Carrion disease, 2024, https://dermnetnz.org/topics/carrion-disease