Rhizopus homothallicus, an emerging pathogen causing cavitary lung lesions

Abstract

Introduction: Rhizopus homothallicus is an emerging pathogen that causes pulmonary mucormycosis.

Case presentation: We report a case of pneumonia caused by R. homothallicus in a 54-year-old type 2 diabetic patient. The organism was isolated from bronchoalveolar lavage fluid and preliminarily identified by fungal morphology and finally by sequencing of the internal transcribed spacer region.

Conclusion: Mucormycosis may be associated with cavitary lung lesions against a backdrop of poorly controlled diabetes or other immunosuppressed states. Pulmonary mucormycosis may have variable clinical and radiological presentations. Therefore, strong clinical suspicion and prompt management can address the high fatality associated with the disease.

Keywords: Rhizopus homothallicus; cavitary; mucormycosis; pulmonary.

Fig. 1.

(a) Chest radiograph (first spot) showing non-homogenous opacification of right mid-lower zone with air bronchogram and obscured right costophrenic angle and right hemidiaphragm s/o Lobar pneumonia. HRCT of the chest with mediastinal and lung windows (second to fourth spots) showing dense opacification of right lower lobe (white arrow) limited by horizontal fissure s/o lobar pneumonia with multiple irregular cavities within it (long black arrow). Patchy area of consolidation seen in right upper lobe on coronal image (curved black arrow). (b) KOH mount of bronchoalveolar lavage, with arrows showing broad non-septate hyphae, which gives presumptive evidence for mucormycosis. (c) Lactophenol cotton blue (LPCB) mount showing R. homothallicus with characteristic golden brown, globose zygospores with stellate spines and suspensor cells (100×).

Fig. 2.

Phylogenetic tree constructed using mega X. The reference strains are represented by red dots and the strain under study is represented by a green square.