Clinical History
This 51-year-old woman presents with pneumonia. She had undergone a bone marrow transplant within the
recent past. Radiologic studies show bilateral diffuse pulmonary infiltrates. A bronchoalveolar lavage
was performed and Diff-Quik, Pap and GMS stains were prepared from cytospin preparations. (Images MRH-A
1, MRH-A 2, MRH-A 3)
Case 3 - Figure 1 - Diff Quik, Low Power 20X: This Diff Quik stained cytospin is cellular with numerous neutrophils and occasional pulmonary macrophages and lymphocytes. From this power no organisms could be identified and no viral cytopathic effect was seen.
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Case 3 - Figure 2 - Diff Quik, High Power 100X: The oil immersion view at 100X shows the intracellular organisms.with in the cytoplasm of the neutrophils. The tachyzoites are about oval to round, 6 microns in size with blue cytoplasm and a central or eccentric nucleus.
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Case 3 - Figure 3 - Diff Quik, High Power 100X: The oil immersion view at 100X shows the intracellular organisms.with in the cytoplasm of the neutrophils. The tachyzoites are about oval to round, 6 microns in size with blue cytoplasm and a central or eccentric nucleus.
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Cytologic Findings
Cytospins from the bronchoalveolar lavage are cellular with acute inflammation, pulmonary macrophages
with abundant foamy cytoplasm, monocytes and occasional lymphocytes. Staining with GMS for fungal
organisms and PCP is negative as is later staining for acid fast bacilli. No evidence of viral
intranuclear inclusions are seen. On close examination, intracytoplasmic organisms are noted within
occasional neutrophils and rarely within monocytes. No free organisms or cysts are seen. The
intracytoplasmic organisms are small (approximately 6 microns), crescent shaped with blue cytoplasm and a
central to eccentrically placed nucleus. These findings are consistent with the tachyzoites of Toxoplasma gondii.
History and Clinical Follow-up
The patient was a 51 year old who had undergone related T cell depleted allogenic peripheral stem cell
transplant for a recurrent follicular small cleaved B-cell lymphoma. The transplant was performed
without complication. Immediately following the transplant she developed a febrile neutropenia but
cultures were negative but she was stated on a prophylactic dose of Vancomycin. She was discharged to
clinic follow-up and 41 days post transplant developed increasing fever and symptoms of pneumonia. Blood
and urine cultures were negative and symptoms worsened despite antibiotic therapy. BAL was obtained
which was reported as having acute inflammation but no organisms were identified. Despite intensive care
the patient died shortly after admission. Autopsy revealed the presence of toxoplasma cysts within brain
tissue and review of the BAL revealed the organisms as described above.
Diagnosis: Toxoplasma pneumonia
Discussion
Toxoplasma goondi is an obligate intracellular protozoan that exists in
three life forms: oocysts, tachyzoites (trophozoites) and tissue cysts. The complete life cycle takes
place only in felines. Infectious sporulated oocysts shed in cat feces can remain infectious for more
than a year and the ingestion of food or beverages contaminated with these oocysts is a primary route of
human infection. Tachyzoites released from the oocysts after ingestion disseminate throughout the body
and are capable of infecting every kind of mammalian cell. In immunocompetent hosts the infection is
generally asymptomatic and as many as 50% of adults in the U.S. have IgG antibodies to this parasite.
Interestingly, the host immune response most often does not completely eliminate the organism from the
body. Instead tissue cysts are formed, most commonly found in the brain, skeletal muscle and cardiac
muscle. The presence of this latent infection explains the reactivation of the disease in
immunocompromised individuals as well as the fact that the disease can be transmitted through solid organ
transplantation.
In immunocompromised patients toxoplasmosis may occur as either a newly acquired (acute) infection or,
as is usually the case, from the reactivation of a latent infection through the release of organisms from
tissue cysts. In AIDS patients with IgG antibodies to T. gondii, toxoplasma
encephalitis occurs in 33-50% when the CD-4 counts fall below 100/mm3. In contrast, in HIV positive
patients, other organ involvement is uncommon. However pulmonary toxoplasmosis has been increasingly
recognized in both HIV as well as in immunocompromised transplant patients. The clinical manifestations
of toxoplasma pneumonia are nonspecific and generally similar to those seen with PCP. Bilateral
interstitial pneumonia is most frequently described although other findings such as single or nodular
infiltrates, cavitary lesions, lobar pneumonia or pleural effusions can also occur. The onset of the
pneumonia tends to be more rapid than seen in PCP and even with treatment is often fatal. In a review of
bone marrow transplant patients with pulmonary toxoplasmosis 92% died, approximately 50% within 3 days of
the onset of pulmonary symptoms.
The diagnosis of pulmonary toxoplasmosis is quite difficult and as was the case in the patient
presented here, is often made post mortum. The fact that toxoplasmosis is a rare complication in BMT
recipients makes the clinical suspicion low and specific tests such as PCR are often not done.
Examination of BAL specimens for the free or intracellular tachyzoites has been touted for the diagnosis
but this has a low sensitivity. A review of the literature in 1999 identified only 59 cases of
toxoplasmosis following BMT with 27 cases having pulmonary involvement. [2] The ante-mortum
diagnosis of toxoplasmosis was made in only 1/3 of these patients. A review in 2002 found 110 published
cases of systemic toxoplasmosis following BMT. An ante-mortum diagnosis was made in 47% of these with a
mortality of 66%. [1] Microscopic examination of BAL fluid was the most common method to make
the diagnosis. Direct immunofluorescence was less sensitive than microscopy and culture was not useful.
The most sensitive method to make the diagnosis is PCR analysis, which will probably become the method of
choice. Because of the very high mortality in these patients it is important to carefully examine any
BAL specimen from an immunocompromised patient for these organisms. The organisms are detectable at 40X
and are best seen under oil immersion at 100X. Scanning at lower powers will not identify the free or
intracellular tachyzoites.
Differential Diagnosis
The differential diagnosis of pulmonary toxoplasmosis includes a number of infectious organisms. Most
bacterial, viral and fungal organisms can be excluded through culture and microscopic examination. Once
the organisms of T. gondii are identified in a pulmonary specimen there is
little that can be confused with them. The intracellular spores of Histoplasma
capsulatum can bear some resemblance to the tachyzoites. However, in histoplasmosis these small
yeast forms will stain with PAS and GMS and may demonstrate budding. The T.
gondii organisms do not stain with either PAS or GMS. The basophilic cytoplasmic inclusions of
cytomegalovirus infected cells can mimic T. gondii but will not show the
characteristic nucleus and cytoplasm of the true tachyzoite. Also these CMV infected cells will almost
always contain the large intranuclear viral inclusions. Other tissue parasites such as Leishmania and Trypanosoma may also exhibit
intracellular forms similar to T. gondii. The absence of a kinetoplast
differentiates the tachyzoite of T. gondii from the amastigotes of either of
these organisms. Finally, as always, precipitated stain artifact, debris or fibrin must be distinguished
from true organisms.
References
- Mele A, Paterson PJ, Prentice HG, Leoni P, Kibbler CC. Toxoplasmosis in bone marrow transplantation: a report of two cases and systematic review of the literature. Bone Marrow Transplant. 2002 Apr;29(8):691-8
- Sing A, Leitritz L, Roggenkamp A, Kolb HJ, Szabados A, Fingerle V, Autenrieth IB, Heesemann J. Pulmonary toxoplasmosis in bone marrow transplant recipients: report of two cases and review. Clin Infect Dis. 1999 Aug;29(2):429-33
- Arnold SJ, Kinney MC, McCormick MS, Dummer S, Scott MA.Disseminated toxoplasmosis. Unusual presentations in the immunocompromised host. Arch Pathol Lab Med. 1997 Aug;121(8):869-73
- Montoya JG and Liesenfeld O. Toxoplasmosis. Lancet. 2004 Jun12;363(9425):1965-76
- Gordon SM, Gal AA, Hertzler GL, Bryan JA, Perlino C, Kanter KR.Diagnosis of pulmonary toxoplasmosis by bronchoalveolar lavage in cardiac transplant recipients. Diagn Cytopathol. 1993 Dec;9(6):650-4
- Bonilla CA, Rosa UW. Toxoplasma gondii pneumonia in patients with the acquired immunodeficiency syndrome: diagnosis by bronchoalveolar lavage. South Med J. 1994 Jun;87(6):659-63
- Barcan LA, Dallurzo ML, Clara LO, Valledor A, Macias S, Zorkin E, Gerona S, Livellara B. Toxoplasma gondii pneumonia in liver transplantation: survival after a severe case of reactivation. Transpl Infect Dis. 2002 Jun;4(2):93-6
- Mariuz P, Bosler EM, Luft BJ. Toxoplasma pneumonia. Semin Respir Infect. 1997 Mar;12(1):40-3
