Discussion
Pulmonary cryptococcosis presenting with multiple cystic lesions is a
rare phenomenon. Moreover, in our patient, the lesions enlarged after
the initiation of treatment although cryptococcosis was controlled. Our
experience shows that pulmonary cryptococcosis might present with
multiple cystic lesions during the course of treatment. Moreover, new
clinical symptoms such as exertional dyspnea might be observed and
careful follow-up is required after treatment.
Cryptococcosis occurs in both immunocompetent and immunocompromised
individuals2. The radiographic features of pulmonary
cryptococcosis are varied, depending on the immunological status of the
host1. Patients with RA show immunodeficiency due to
drug treatment and autoimmune inflammation, as well as variable CT
findings and distribution in pulmonary
cryptococcosis4,5.
In pulmonary cryptococcosis, cavitation is occasionally detected on CT,
especially in immmunocompromised patients1. There have
been few case reports of pulmonary cryptococcosis with multiple cystic
lesions. A lung cyst is defined as any round circumscribed space
surrounded by an epithelial or fibrous wall of variable thickness that
usually measures less than 3 mm. It can be distinguished from a cavity
in which the wall thickness is greater than 3 mm6. The
radiographic findings in the present case presented as cysts. Takata et
al. reported a case of secondary pulmonary cryptococcosis presenting
with multiple cystic shadows in a patient with RA, with size reduction
of cystic lesions after the initiation of treatment7.
However, in our case, the cystic lesions became coalesced with each
other, taking on a thin-walled state, and became enlarged, despite
improvement in clinical manifestation and antigen titer. A previous
report has indicated that the radiologic resolution of pulmonary
cryptococcosis following antifungal therapy is usually gradual and
incomplete3. Residual abnormalities, including
bronchiectasis, cavitation, and/or fibrotic scars, are frequently
observed, most notably on CT3.
We speculated that the mechanism of the formation and development of
cysts in this case refer to the etiology of other diseases presenting
with multiple cystic lesions. Pathologically, most nodules and masses
seen on radiographic patterns in pulmonary cryptococcosis are
characterized by granulomatous reactions. Langerhans cell histiocytosis
(LCH) is characterized by the infiltration of Langerhans cells mainly in
the lungs, leading to the activation of an inflammatory process with
potential dysfunction in the affected sites8.
Granuloma formation in LCH is similar to the distribution of pulmonary
cryptococcosis9. The pathogenesis of pulmonary cysts
in LCH is speculated to be peribronchiolar distribution of granulomatous
inflammation and fibrosis, leading to a check-valve
mechanism9. Regarding the pathogenesis of cystic
changes in infectious lung disease such as Pneumocystisjirovecii pneumonia in HIV-infected patients and staphylococcal
pneumonia, a check-valve mechanism and excavation of necrotic material
via draining bronchi play an important role in forming cystic
lesions10,11.
Therefore, cystic changes in the present case might have been caused by
transbronchial discharge of necrotic material and granulomatous
involvement and fibrosis of the bronchioles, leading to a check-valve
mechanism.
In conclusion, multiple cystic lung lesions that enlarge after treatment
are a rare manifestation of pulmonary cryptococcosis. Even if infection
control of cryptococcosis is achieved after the initiation of treatment,
clinicians should continue to observe the patients carefully.