MUCORMYCOSIS

In India, after COVID second wave, there is a new disease named Mucormycosis also known as black fungus, has been making headline.

Well what is it? Today we will talk about it. It is a type of Opportunistic specifically nosocomial infection, affecting mainly doctors. It is fungal in nature.

Let’s get into it more.

Mucormycosis is an invasive disease caused by phycomycetes, mainly by Rhizopus, Mucor and Absidia. It used to be a rare terminal complication of uncontrolled diabetes and other chronic debilitating diseases. The incidence of the disease has increased considerably as a result of the widespread use of antibiotics, steroids and antimetabolites. The fungi are normally avirulent and are able to invade tissues only when general resistance is extremely low.

PATHOLOGY

Spore of fungi causing mucormycosis are found ubiquitously in the environment. Transmission occurs via inhalation, inoculation or rarely ingestion of spores. Spores develop into mycelial from containing wide aseptate hyphae which are angioinvasive in nature resulting in spread of infection. The primary infection is usually in the upper respiratory tract or nose, where the spores germinate and mycelia invade the adjacent tissue – the orbit, sinuses and the brain. Primary infection may also occur in the lung, the fungi invading the arteries to cause thrombosis and infarction. The disease is fetal.

Predisposing factors : Agents of mucormycosis require iron as growth factor. Hence conditions with increased with increased iron load are at higher risk of developing invasive mucormycosis.

  • Diabetic ketoacidosis (DKA) is the most important risk factor. Acidosis causes release of iron from the sequestrated proteins in serum.
  • End stage renal disease.
  • Patients taking iron therapy or deferoxamine (iron chelator).
  • Defects in phagocytic function {e.g. neutropenia(condition in which neutrophils becomes less) or steroid therapy}.

CLINICAL MANIFESTATION

Agents of mucormycosis are angioinvasive (invasive in blood vessel) in nature. Mucormycosis has six types of clinical presentations.

  1. Rhinocerebral mucormycosis : It occurs commonly in patients with diabetic ketoacidosis. It is the most common form; starts as eye and facial pain, may progress to cause orbital cellulitis, proptosis and vision loss.
  2. Pulmonary mucormycosis is the second most common form, occurs in patients with leukemia.
  3. Cutaneous mucormycosis.
  4. Gastrointestinal mucormycosis is the second most common form, occurs in patients with leukemia.
  5. Disseminated mucormycosis : Brain is the most common site of dissemination, but can affect any organ.
  6. Miscellaneous forms : Any body site may be randomly affected such as bones, trachea and kidneys, etc.

Diagnosis is usually made during histological examination of autopsy material, by the presence of broad, non septate mycelia in tissues. The fungi can be grown easily on Sabouraud’s medium without cycloheximide. Mucor shows branched sporangiophores arising randomly along aerial mycelium. Rhizoids are absent. Rhizopus has rhizoids, and sporangiophores arise in groups directly above the rhizoids.

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