Cryptococcosis

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Hi there!

You’re looking at a short reference article from Explain Medicine (one of four distinct learning formats available in Clinical Odyssey). Try it out, and have fun improving your clinical skills.

Medicine

Last updated on:
August 13^th, 2021

Medicine

Last updated on:
August 13^th, 2021

Hi there!

You’re looking at a short reference article from Explain Medicine (one of four distinct learning formats available in Clinical Odyssey). Try it out, and have fun improving your clinical skills.

Clinical: History

Fact	Explanation
Introduction	Cryptococcosis is a fungal opportunistic infection that mainly occurs in HIV-infected individuals and persons under immunosuppression. The organism is acquired by inhalation and the lung is the first site of infection. Meningitis is the most common clinical manifestation; this is due to neurotropism of the causative organism.
Etiology	Cryptococcus neoformans causes the majority of infections. C. neoformans is an encapsulated yeast that can be found in pigeon droppings and soil samples from around the world. The capsule can be visualized in a suspension of India ink when examined under a microscope. C. neoformans produces white mucoid colonies on a variety of agars; these usually become easily visible within 48 hours.
Predisposing factors	HIV infection is the major predisposing factor for cryptococcal meningitis; the highest incidence is in patients with AIDS and a CD4 cell count of <100 cells/μL. In patients without HIV infection, key predisposing factors include prolonged steroid treatment, immunosuppressive therapy, solid organ transplantation, hematological malignancies, sarcoidosis, and immunological disorders—especially CD4 lymphopenia.
Pathogenesis	Cryptococci enter the body via the lungs. They are transported within mononuclear phagocytes in the blood and disseminate in cerebral vessels crossing the blood-brain barrier. In HIV-associated cryptococcal meningitis, HIV infection of macrophages facilitates their translocation into the CNS.
Fever	Fever is present in 50% of patients. This is due to the inflammatory response triggered by the yeast.
Meningeal signs	Stiff neck, photophobia, and vomiting are seen in one-fourth to one-third of patients. They are due to meningeal irritation and increased intracranial pressure.
Headache	Headache is one of the most common symptoms. It is due to the increased intracranial pressure or the mass effect of cryptococcomas.
History of exposure	Since C. neoformans is commonly found in pigeon droppings, the patient should be questioned regarding the possible recent exposure.

Introduction

Cryptococcosis is a fungal opportunistic infection that mainly occurs in HIV-infected individuals and persons under immunosuppression. The organism is acquired by inhalation and the lung is the first site of infection. Meningitis is the most common clinical manifestation; this is due to neurotropism of the causative organism.

Etiology

Cryptococcus neoformans causes the majority of infections. C. neoformans is an encapsulated yeast that can be found in pigeon droppings and soil samples from around the world. The capsule can be visualized in a suspension of India ink when examined under a microscope. C. neoformans produces white mucoid colonies on a variety of agars; these usually become easily visible within 48 hours.

Predisposing factors

HIV infection is the major predisposing factor for cryptococcal meningitis; the highest incidence is in patients with AIDS and a CD4 cell count of <100 cells/μL. In patients without HIV infection, key predisposing factors include prolonged steroid treatment, immunosuppressive therapy, solid organ transplantation, hematological malignancies, sarcoidosis, and immunological disorders—especially CD4 lymphopenia.

Pathogenesis

Cryptococci enter the body via the lungs. They are transported within mononuclear phagocytes in the blood and disseminate in cerebral vessels crossing the blood-brain barrier. In HIV-associated cryptococcal meningitis, HIV infection of macrophages facilitates their translocation into the CNS.

Fever

Fever is present in 50% of patients. This is due to the inflammatory response triggered by the yeast.

Meningeal signs

Stiff neck, photophobia, and vomiting are seen in one-fourth to one-third of patients. They are due to meningeal irritation and increased intracranial pressure.

Headache

Headache is one of the most common symptoms. It is due to the increased intracranial pressure or the mass effect of cryptococcomas.

History of exposure

Since C. neoformans is commonly found in pigeon droppings, the patient should be questioned regarding the possible recent exposure.

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