Pneumocystsis jirovecii

Question 1

morphology

Answer 1

Yest that used to be thought a protozoan.
It’s yeast-like and unicellular.

Can exists as a ‘trophozoite’ yeast form, a uni-nuclear sprorocyst, or cyst with 8-fusiform inracystic bodies.

It’s lifecycle and reservoir is not known.

Question 2

Infection and transmission

Answer 2

Infects respiratory tract, transmitted by respiratory drops.

Exclusively in IC’d patients, specifically AIDS patients with CD4 count below 200.

Question 3

Clinical presentation

Answer 3

Fast onset pneumonitis.
Diffuse INTERSTITIAL pneumonia, without consolidations in the alveoli.

dyspnea, non-productive cough, fever.

groundglass lesions on X-ray, or nothing at all on x-ray

It is primarily a lung disease, but it may disseminate in rare cases to the 
lymph nodes
spleen
bone marrow
liver

Question 4

Diagnosis

Answer 4

BAL: Bronchialveolar Lavage,
and
Grocott silver stain showing yeast in the washings

Question 5

Treatment

Answer 5

prophylaxis with trimethoprim and sulfamethoxazole
In this case its usually called Bactrim.

or

Pentamidine if the patient has Sulfa allergy.