Fungi in megakaryocytes. An unusual manifestation of fungal infection of the bone marrow

Megakaryocytes respond during sepsis and display innate immune cell behaviors

Megakaryocytes (MKs) are precursors to platelets, the second most abundant cells in the peripheral circulation. However, while platelets are known to participate in immune responses and play significant functions during infections, the role of MKs within the immune system remains largely unexplored. Histological studies of sepsis patients identified increased nucleated CD61+ cells (MKs) in the lungs, and CD61+ staining (likely platelets within microthrombi) in the kidneys, which correlated with the development of organ dysfunction. Detailed imaging cytometry of peripheral blood from patients with sepsis found significantly higher MK counts, which we predict would likely be misclassified by automated hematology analyzers as leukocytes. Utilizing in vitro techniques, we show that both stem cell derived MKs (SC MKs) and cells from the human megakaryoblastic leukemia cell line, Meg-01, undergo chemotaxis, interact with bacteria, and are capable of releasing chromatin webs in response to various pathogenic stimuli. Together, our observations suggest that MK cells display some basic innate immune cell behaviors and may actively respond and play functional roles in the pathophysiology of sepsis.

Cryptococcus neoformans osteomyelitis of the calcaneus: Case report and literature review

Cryptococcus neoformans is an encapsulated, yeast-like fungus that can cause a systemic mycosis, particularly in immunocompromised patients. Disseminated infections typically affect the central nervous system, and osseous lesions are infrequent. Only 5%–10% of disseminated cryptococcosis involves bones. A 69-year-old female presented pain, swelling, and a soft tissue mass in her right lateral hindfoot. Her medical history included a kidney transplant (10 years earlier) secondary to chronic disease due to IgA nephropathy. The patient underwent an excisional biopsy, surgical debridement, and secondarily negative pressure wound therapy to achieve skin closure. Biopsy revealed a rare Cryptococcus neoformans osteomyelitis of the calcaneus. The patient then received IV treatment with liposomal amphotericin B at 3 mg/kg/d for 25 days. In conclusion, we present a case of cryptococcal osteomyelitis which, although not a frequent disease, must be considered as one of the differential diagnoses of osteolytic osseous lesions in patients with chronic osteomyelitis. Cryptococcus neoformans may be a potential cause of below-knee infection, mainly in immunocompromised patients.

Cryptococcosis

In the past 2 decades, Cryptococcus has emerged in its clinical significance and as a model yeast for understanding molecular pathogenesis. C neoformans and C gattii are currently considered major primary and secondary pathogens in a wide array of hosts that are known to be immunocompromised or apparently immunocompetent. A recent outbreak of C gattii infections further underscores the clinical importance of the yeast through its epidemiology and pathogenicity features. With an enlarging immunosuppressed population caused by HIV infection, solid organ transplantation, and clinical use of potent immunosuppressives, such as cancer chemotherapy, monoclonal antibodies, and corticosteroids, this fungus has become a well-established infectious complication of modern medicine. This article examines current issues in cryptococcal infections, including new classification, epidemiology, pathogenesis, and specific clinical aspects.

Bone marrow manifestations of infections and systemic diseases observed in bone marrow trephine biopsy review

Bone marrow modifications resulting from infections and systemic diseases can be studied by analysis of morphology and aetiology. Two types of lesions or modifications can be observed, those occurring in the connective tissue comprising inflammatory processes, acute and chronic, as well as immune reactions, and those involving the normal haematopoietic cell lines, with possible hyperplastic or aplastic changes in one or more cell lines. The main lesions are described (oedema, haemorrhage, necrosis, suppuration, granulomas, lymphoid nodules and hyperplasia, immunoblastic or plasmacytic hyperplasia), as well as the main aetiologies. In association, the three main haematopoietic cell lines show hyperplasia, hypoplasia, aplasia of one or all of the cell lines, sometimes with dysmyelopoiesis. The stroma and vessel reactions comprise myelofibrosis, gelatinous transformation or amyloid deposits. The methods for identifying aetiological agents are emphasized. It should also be stressed that malignant neoplasias of different types involving the bone marrow can be responsible for such inflammatory or immune reactions.