Malassezia restricta Pneumonia in Solid Organ Transplant Recipients: First Report of Two Cases

Malassezia restricta as an unexpected cause of infectious osteomyelitis diagnosed by metagenomic sequencing: a case report and literature review

BACKGROUND

Malassezia restricta, a lipophilic and lipodependent yeast belonging to the basidiomycetes group, is an opportunistic fungal pathogen associated with various skin diseases, including seborrheic dermatitis and dandruff. Typically, Malassezia infection in neonates manifests as fungemia or hematogenous dissemination to the bone or lungs. However, vertebral osteomyelitis caused by these fungi is rarely reported owing to non-specific clinical presentations and laboratory/imaging findings. The Pathogen Metagenomics Sequencing (PMseq) technique enables direct high-throughput sequencing of infected specimens, facilitating the rapid and accurate detection of all microorganisms in clinical samples through comprehensive reports.

CASE PRESENTATION

A 52-year-old male was admitted to our hospital on July 20, 2022 with a 3-month history of ambulatory difficulties and localized low back pain. Magnetic Resonance Imaging (MRI) examination of the spinal column revealed irregular bone destruction affecting the L2, L3, and L5 vertebral bodies. Additionally, low T1 and high T2 intensity lesions were observed at the intervertebral discs between L3 and L5. The presumptive diagnosis of tuberculous spondylitis was made based on the imaging findings, despite negative results in all mycobacterium tests. However, the patient exhibited no improvement after receiving regular anti-tuberculosis treatment for 3 months. Subsequent MRI revealed an expansive abnormal signal within the vertebral body, leading to progressive bone destruction. The absence of spinal tuberculosis or other infective microorganisms was confirmed through culture from blood and pathological tissue from the L4 vertebral body. Subsequently, PMseq was performed on the specimens, revealing M. restricta as the predominant pathogen with the highest relative abundance value. The pathological examination revealed the presence of fungal mycelium in the L4 vertebral body, with positive findings on periodic Schiff-methenamine and periodic acid-Schiff staining. The anti-tuberculosis treatment was discontinued, and an antifungal combination of fluconazole and voriconazole was administered. All symptoms were resolved after 7 consecutive months of treatment, and the patient was able to ambulate autonomously. Vertebral lesions were reduced on MRI during the 13-month follow-up.

CONCLUSIONS

M. restricta is not a commonly recognized pathogen associated with infectious vertebral osteomyelitis. However, PMseq can aid in diagnosis, timely treatment, and decision making for some non-specific infectious diseases.

Oral Malassezia infection co-occurring with tinea versicolor: metagenomic sequencing of the saliva

Malassezia is a lipid-dependent cutaneous symbiotic fungal genus associated with tinea versicolor. Here, we first present a rare case of a young tinea versicolor patient with oral manifestations presenting as white strips, patches, and pigmentation. The patient had a family history of tinea versicolor and a habit of frequent intake of cream. Histopathologic features and periodic acid-schiff staining of oral lesion indicated oral infection with round budding yeasts with short hyphae. Saliva metagenomic sequencing identified Malassezia and demonstrated the upregulated amount, diversity and activity of inflammatory bacteria. The clinical manifestations of oral Malassezia infection and changes in bacterial communities shed light on the pathogenic role of Malassezia in oral mucosa. In conclusion, we report the first oral Malassezia infection, which broadens the pathogenic cognitive scope of Malassezia and highlights the value of molecular techniques in the diagnostic process.