A Review on: Mucormycosis -from the Pathogens to the Disease

Mucormycosis is a group of fungal infections caused by Zygomycetes, within the Mucorales order, and can occur in various forms, including rhino-orbitocerebral, pulmonary, gastrointestinal, cutaneous, and disseminated infections. Pulmonary mucormycosis is the second most frequent manifestation. This study examines the demographics, clinical features, diagnostic methods, radiologic findings, treatments, and outcomes associated with pulmonary mucormycosis. Mucormycosis is the second most common invasive fungal infection after aspergillosis, with an increasing incidence reported in certain countries. This term refers to diseases caused by filamentous fungi within the Mucorales order. People at higher risk include those with poorly controlled diabetes, immunocompromised individuals such as patients undergoing treatment for hematologic cancers or those receiving solid organ or hematopoietic stem cell transplants, as well as individuals who have suffered severe trauma to soft tissues, often with direct contamination of the wound by organic material.  The clinical presentation of mucormycosis varies based on the host's immune status. For example, patients with diabetes typically develop rhino-orbital-cerebral mucormycosis (ROCM), while those with hematologic malignancies often present with sino-pulmonary disease. Trauma patients commonly develop necrotizing infections of the skin and soft tissues. Across all forms of mucormycosis, the infection is characterized by aggressive tissue destruction and infarction due to angioinvasion. Involvement of the central nervous system (CNS) is one of the most serious forms of the disease, often determining both survival and long-term outcomes for affected patients.

OBJECTIVE:

This study aims to characterize the demographics, clinical presentation, diagnostic methods, radiologic findings, treatment approaches, and outcomes of patients with pulmonary mucormycosis. Mucormycosis is an emerging, life-threatening fungal infection caused by Mucorales species. It predominantly affects immunocompromised individuals, particularly those with hematological malignancies, organ transplants, or diabetes mellitus. The most common forms of mucormycosis are rhino-orbito-cerebral and pulmonary. Interestingly, the location of the infection is often linked to the patient's underlying condition: pulmonary mucormycosis is more frequently seen in individuals with hematologic cancers, while rhino-orbito-cerebral mucormycosis is more commonly associated with diabetes. Cutaneous mucormycosis typically results from direct fungal inoculation following trauma or surgery. Gastrointestinal mucormycosis occurs after ingesting contaminated food or through the use of contaminated medical devices, affecting the stomach or colon. The disseminated formof the infection is the most severe, often seen in patients with significant immunosuppression. There are also rare presentations of mucormycosis affecting the heart (endocarditis), bones and joints (osteoarticular), or isolated cerebral infections. Healthcare-associated mucormycosis is a particular concern in premature newborns and burn unit patients. Clinical symptoms and CT scan findings are not highly specific, although the early appearance of a reversed halo sign is associated with pulmonary mucormycosis. A promising new diagnostic tool involves the detection of Mucorales DNA in the bloodstream, which could enhance early diagnosis and prompt treatment. Treatment should include antifungal therapy, addressing the underlying condition, and surgical intervention when appropriate.

Mucormycosis In Covid 19

Coronavirus Disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been linked to various opportunistic bacterial and fungal infections. Aspergillus and Candida are the primary fungal pathogens responsible for co-infections in COVID-19 patients. Recently, there has been a significant increase in cases of mucormycosis among people with COVID-19, particularly in India. The factors contributing to the growth of Mucorales spores in these patients include a combination of low oxygen levels (hypoxia), high blood glucose (due to diabetes, new-onset hyperglycemia, or steroid-induced hyperglycemia), acidic conditions (such as metabolic acidosis and diabetic ketoacidosis), elevated iron levels (high ferritin), and reduced white blood cell (WBC) function due to immunosuppression (from the SARS-CoV-2 virus, steroids, or underlying comorbidities). Additional risk factors include prolonged hospitalizations and mechanical ventilation. Mucormycosis, initially described as phycomycosis or zygomycosis in 1885 by Paltauf and later named by American pathologist Baker in 1957, is an aggressive infection caused by molds from the genera Rhizopus, Mucor, Rhizomucor, Cunninghamella, and Absidia of the Mucorales order. The most common species, Rhizopus oryzae, is responsible for approximately 60% of mucormycosis cases and accounts for 90% of rhino-orbital-cerebral mucormycosis (ROCM) cases. Infection occurs primarily through the inhalation of fungal spores.

An unusual outbreak of mucormycosis took place in India during the second wave of COVID-19 in the spring of 2021. COVID-19-associated mucormycosis (CAM), particularly rhino-orbital-cerebral mucormycosis (ROCM), was predominantly observed in patients with poorly controlled diabetes who had been treated with excessive doses of glucocorticoids.