We report a patient who presented with recalcitrant ulcerated papules and plaques on both legs. Histopathology revealed protothecosis, and subsequent culture of the lesions grew Prototheca wickerhamii. Gradual resolution of the ulcers occurred on treatment with itraconazole.

In April 2017, an 81-year-old man presented to the emergency department with acute urinary retention. Digital rectal examination revealed a grossly enlarged prostate with a hard nodule felt at the left lobe. The patient was subsequently catheterised and haematuria with a small number of blood clots was noted. Urine cytology and microbiology were negative. Prostate-specific antigen (PSA) was elevated at 23.8 ng/mL.Cystoscopy revealed a trabeculated urinary bladder with multiple small bladder diverticula but no mucosal lesion and a grossly enlarged prostate. The patient was prescribed terazosin and successfully weaned off the Foley catheter. However, the patient required repeat admissions for recurrent acute urinary retention. He was managed with an increased dose of terazosin and intermittent selfcatheterisation.Computed tomography (CT) urogram was performed as part of the haematuria examination and revealed an approximately 10-cm hypodense cystic lesion in the rectovesical space. No preserved fat plane was present between the lesion and seminal vesicles and prostate, or the lesion and rectum. Internal enhancing solid components were seen in the left posterior aspect of the mass (Fig a and b).On magnetic resonance imaging (MRI), the mass was again noted between the rectum and the prostate. The mass showed predominantly T1-weighted hyperintense signal which could represent proteinaceous or blood product. In T2weighted sequence, the mass was heterogeneously hyperintense. A solid component previously detected on CT scan demonstrated T1-and T2weighted intermediate signal intensity, with restricted diffusion and contrast enhancement. (Fig c to g) The differential diagnoses included a seminal vesicle or prostatic tumour, a rectal tumour such as gastrointestinal stromal tumour, or a neuroendocrine tumour.A CT-guided biopsy was performed for histology. The centre of the mass was first biopsied and yielded old blood products. Cytology revealed necrotic cells and blood cells but no tumour cells.Hong Kong Med J 2020;26:66-9 https://doi.