DOI:10.2214/AJR.07.2074
AJR 2007; 189:177-186
© American Roentgen Ray Society
The Many Faces of Pulmonary Nontuberculous Mycobacterial Infection
Santiago Martinez1,
H. Page McAdams1 and
Chandra S. Batchu2
1 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC
27710.
2 Department of Radiology, St. Francis Hospital, Evanston, IL.
Received February 19, 2007;
accepted after revision February 22, 2007.
Address correspondence to S. Martinez.
CME
This article is available for CME credit. See
www.arrs.org
for more information.
Abstract
OBJECTIVE. The purpose of this article is to review clinical and
radiologic manifestations of pulmonary nontuberculous mycobacterial
infection.
CONCLUSION. Common and well-recognized patterns of infection include
cavitary and bronchiectatic disease and infection in AIDS patients. Less
common or well-recognized manifestations include nodules or masses mimicking
malignancy, hypersensitivity pneumonitis, and others. Definitive diagnosis can
be difficult and patterns may overlap. Timely diagnosis requires a high index
of suspicion and knowledge of the spectrum of clinical and radiologic
features.
Keywords: chest • lung • mycobacterial infection
Introduction
Nontuberculous mycobacteria were initially isolated shortly after
Mycobacterium tuberculosis was isolated in the 19th century
[1]. Although multiple reports
in the first half of the 20th century describe human infection by
"unusual," "unclassified," or "anonymous"
mycobacteria, it was not until the 1950s that larger series began to confirm
the nontuberculous mycobacteria as true human pathogens
[1]. During the 1970s and early
1980s, Christensen et al.
[2-4]
showed the similarity of Mycobacterium avium-intracellulare complex
(MAC) and Mycobacterium kansasii infection to postprimary pulmonary
tuberculosis. This pattern of infection was subsequently termed
"cavitary" or "classic" when an unusual form of the
disease, later termed the "nonclassic"
[5] or
"bronchiectatic"
[6] form, was described in the
mid 1980s [7].
Epidemiology
By the early 1980s, the prevalence of non-tuberculous mycobacterial disease
in the United States was estimated to be 1.8 cases per 100,000 inhabitants.
Among nontuberculous mycobacterial isolates, mostly from respiratory
secretions, 61% were MAC; 24%, M. kansasii; approximately 5%,
Mycobacterium fortuitum; and 15%, other nontuberculous mycobacteria
[8]. In the early 1980s,
Zakowski et al. [9] reported an
increasing incidence of MAC infection in patients with HIV infections. During
the 1990s, analysis from the Centers for Disease Control and Prevention showed
a dramatic increase in nontuberculous mycobacteria isolates to levels even
higher than M. tuberculosis (MAC, 34% vs M. tuberculosis,
26%). Mycobacterium gordonae and M. fortuitum were
identified in 18% and 5% of these isolates, respectively
[10]. Although the exact
reason for this apparent increased incidence is not clear, it is believed that
increased clinical recognition and better techniques for diagnosis are at
least partly responsible [11,
12].
Currently, MAC and, to a lesser extent, M. kansasii, account for
most cases of nontuberculous mycobacteria infection among immunocompetent and
immunosuppressed patients in the United States. Mycobacterium xenopi,
Mycobacterium szulgai, and Mycobacterium simiae are less
frequent causes of pulmonary disease. Mycobacterium scrofulaceum,
Mycobacterium fortuitum-chelonei, and M. gordonae may also cause
pulmonary disease but are more commonly isolated elsewhere in the body
[5,
13].
Diagnosis
Definitive diagnoses of pulmonary nontuberculous mycobacteria infection are
difficult. Because the organisms are often saprophytes, they may colonize
airways rather than infect them. Cultures can be falsely positive in patients
with chronic lung disease and falsely negative in infected patients without
cavities [14]. Thus,
identification of acid-fast bacilli at microscopy or isolation of
nontuberculous mycobacteria in culture by itself is not enough evidence for
establishing the diagnosis [6].
Further, there is cross-reactivity between MAC and M. tuberculosis on
the purified protein derivative standard test
[15]. Although many skin tests
for diagnosis of nontuberculous mycobacteria, particularly MAC, have become
available with good results, lack of standardization precludes their use in
clinical practice [15].
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Fig. 1A —54-year-old man with mild emphysema, cough, and fever.
Cultures from sputum and resected surgical specimen showed Mycobacterium
avium-intracellulare complex organisms. Chest radiograph coned to left
upper lung shows well-circumscribed cavitary left upper lobe mass.
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Fig. 1B —54-year-old man with mild emphysema, cough, and fever.
Cultures from sputum and resected surgical specimen showed Mycobacterium
avium-intracellulare complex organisms. Axial CT images (5-mm section,
lung window setting) confirm left upper lobe cavity and show adjacent cluster
of small nodules (arrows, C).
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Fig. 1C —54-year-old man with mild emphysema, cough, and fever.
Cultures from sputum and resected surgical specimen showed Mycobacterium
avium-intracellulare complex organisms. Axial CT images (5-mm section,
lung window setting) confirm left upper lobe cavity and show adjacent cluster
of small nodules (arrows, C).
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The American Thoracic Society (ATS) recently revised and simplified
criteria for diagnosis of nontuberculous mycobacterial lung disease in
HIV-seropositive and seronegative hosts (Appendix 1)
[12].
Microbiologic Perspective
Traditionally, nontuberculous mycobacteria have been classified according
to the Runyon system established in the 1950s. Four groups of nontuberculous
mycobacteria, according to pigmentation and growth rate in culture, are
recognized in this classification. The rapid-growers (group IV), as the name
implies, can be grown in culture and identified in fewer than 7 days
[16,
17]. Conversely, the
slow-growers (groups I-III) take weeks to months to grow in culture. However,
new molecular identification techniques that allow detection and speciation in
a matter of hours are becoming more available
[11,
18]. For these reasons, the
Runyon system is becoming less important clinically
[5,
6]. Speciation has important
clinical and prognostic implications
[19]. For example, infection
with Mycobacterium abscessus, a group IV organism, tends to have an
unpredictable response to medical treatment, and surgical resection may be
attempted when feasible [16].
On the other hand, M. fortuitum, also a group IV organism, is more
susceptible to medical therapy
[11]. Further, conventional
treatment for the slowly growing organisms MAC and M. kansasii are
different. Most treatment regimens for M. kansasii include isoniazid,
whereas those for MAC do not
[11]. Thus, accurate and rapid
speciation is becoming more important than classification according to the
Runyon system. Also of interest is the lack of correlation between in vitro
and in vivo susceptibility shown in some species of nontuberculous
mycobacteria (e.g., M. xenopi and Mycobacterium malmoense)
[20,
21], a fact that raises some
concern regarding the importance of this test.
Clinical and Radiologic Manifestations
The clinical and radiologic manifestations of pulmonary nontuberculous
mycobacteria infection are protean and include the cavitary
("classic") form, bronchiectatic ("nonclassic") form,
infection in immunocompromised patients (HIV and non-HIV), nodules or masslike
opacities, infection in patients with deglutition problems, and
hypersensitivity pneumonitis
[5,
14,
22]. However, these
manifestations are not mutually exclusive; several forms can be seen in an
individual patient. Moreover, new manifestations of disease are occasionally
reported that do not easily fit into these categories. However, this
classification is useful for purposes of discussion and differential
diagnosis, and it will be used here. The cavitary and the bronchiectatic forms
of the disease are responsible for most nontuberculous mycobacteria infections
in the immunocompetent patient
[2,
3,
7,
23,
24]. The true incidence of
other forms of nontuberculous mycobacteria infection is unknown.
Cavitary Form (Classic Infection)
The clinical and radiologic manifestations of the cavitary (or classic)
form of the disease are quite similar to those of postprimary tuberculosis.
This form of the disease is more prevalent among older white men with
underlying chronic pulmonary disease (e.g., chronic obstructive pulmonary
disease)
[2-4,
24]. Some important
predisposing conditions for pulmonary nontuberculous mycobacteria infection
are listed in Appendix 2 [6].
Most cases are caused by MAC, although M. kansasii, and, to a lesser
extent, M. xenopi
[21,
25-27],
M. abscessus [28],
and M. malmoense [20,
29], can also manifest with
this pattern.
Common findings in the chest radiograph include upper lobe cavitary lesions
and endobronchial spread evidenced by nodules adjacent to foci of disease
(Figs. 1A,
1B,
1C,
2A,
2B,
2C,
3A, and
3B), cicatricial atelectasis,
and pleural thickening. In comparison with postprimary tuberculosis, disease
progresses more slowly [5,
14] and cavities are more
likely to be smaller or thin-walled
[2,
14,
23]. CT can further
characterize cavities (usually single with ill-defined margins) and show
associated bronchiectasis and pleural thickening
[5,
30,
31]. As in tuberculosis,
adenopathy and pleural effusion are uncommon manifestations
[7,
24,
32,
33].
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Fig. 2A —36-year-old woman with chronic cough, weight loss, and
fatigue. Cultures from sputum showed Mycobacterium
avium-intracellulare complex organisms. Frontal chest radiograph shows
right upper lobe volume loss and bronchiectasis and poorly defined nodules in
right lower lung. Note also left lower lobe volume loss, heterogeneous
opacity, and left upper lobe bulla.
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Fig. 2B —36-year-old woman with chronic cough, weight loss, and
fatigue. Cultures from sputum showed Mycobacterium
avium-intracellulare complex organisms. Axial CT image (5-mm section,
lung window setting) shows small clustered right upper lobe nodules and cavity
(arrow). Note left upper lobe bullae (asterisks).
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Fig. 2C —36-year-old woman with chronic cough, weight loss, and
fatigue. Cultures from sputum showed Mycobacterium
avium-intracellulare complex organisms. Axial CT image (5-mm section,
lung window setting) obtained at more caudal level shows right lower lobe
tree-in-bud opacities (white arrows) consistent with endobronchial
spread of infection. Note left lower lobe cavity (asterisk) and
bronchiectasis (black arrow).
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Fig. 3A —37-year-old man with chronic cough. Cultures of
bronchoalveolar lavage fluid showed Mycobacterium chelonei organisms.
Axial CT image (1.25-mm section, lung window setting) shows large cavity in
right upper lobe with lobular intracavitary mass. Note ground-glass opacity in
left upper lobe, possibly representing additional focus of infection.
Histopathologic analysis of resected specimen showed necrotic lung in
cavity.
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Fig. 3B —37-year-old man with chronic cough. Cultures of
bronchoalveolar lavage fluid showed Mycobacterium chelonei organisms.
Axial CT image (1.25-mm section, lung window setting) obtained at more caudal
level shows tree-in-bud opacities (arrows) consistent with
endobronchial spread of infection.
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Fig. 4 —73-year-old woman with chronic productive cough and fatigue.
Cultures of bronchoalveolar lavage fluid showed Mycobacterium
avium-intracellulare complex organisms. Axial CT image (1.25-mm section,
lung window setting) shows cylindric bronchiectasis (arrows) and
partial volume loss in right middle lobe and lingula. Note bilateral lower
lobe scattered nodules.
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Fig. 5A —67-year-old woman with chronic cough and weight loss. Sputum
cultures showed Mycobacterium avium-intracellulare complex organisms.
Frontal chest radiograph shows hyperinflation and subtle opacity in right
middle lobe. Note symmetric bilateral apical scarring.
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Fig. 5B —67-year-old woman with chronic cough and weight loss. Sputum
cultures showed Mycobacterium avium-intracellulare complex organisms.
Lateral chest radiograph shows hyperinflation and atelectasis of right middle
lobe.
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Fig. 5C —67-year-old woman with chronic cough and weight loss. Sputum
cultures showed Mycobacterium avium-intracellulare complex organisms.
Axial CT images (1-mm section, lung window setting) show diffuse mosaic
attenuation and bronchiectases. Note atelectasis of right middle lobe and
small peripheral foci of consolidation in left upper lobe.
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Fig. 5D —67-year-old woman with chronic cough and weight loss. Sputum
cultures showed Mycobacterium avium-intracellulare complex organisms.
Axial CT images (1-mm section, lung window setting) show diffuse mosaic
attenuation and bronchiectases. Note atelectasis of right middle lobe and
small peripheral foci of consolidation in left upper lobe.
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Bronchiectatic (Nonclassic) Form
MAC and M. kansasii
[7,
30,
31,
34-37]
are the most common organisms responsible for this form of disease; however,
other mycobacteria such as M. chelonae
[38] and M. abscessus
[16,
28,
39] can manifest in this way.
The infection is more commonly seen among elderly white women with no
predisposing factors [5,
7,
30,
31,
35,
36]. Whether the infection
develops in the setting of preexisting bronchiectasis
[34,
40,
41] or results in
bronchiectasis [42] is
controversial. However, some evidence indicates that bronchiectasis progresses
more rapidly in the setting of infection with nontuberculous mycobacteria
[34,
40]. Infection presents in an
indolent fashion with a chronic cough; constitutional symptoms are uncommon
[5,
35]. Some of these patients
may voluntarily suppress their cough, leading to poor drainage of secretions
and engraftment of nontuberculous mycobacteria, the so-called Lady Windermere
syndrome [36,
43]. Because sputum cultures
are not sensitive for diagnosis in this form of the disease, more invasive
studies such as bronchoalveolar lavage and biopsy may be required
[44]. On histopathologic
examination, bronchiolectasis and bronchiolar and peribronchiolar inflammation
with or without granuloma formation are seen
[45].
Radiographic findings include randomly distributed nodular opacities;
cavitation is uncommon [7]. CT
characteristically shows small centrilobular nodules or tree-in-bud opacities,
with cylindric bronchiectasis, usually in the same lobe
[28,
30,
37,
42,
46]
(Fig. 4). Although the right
middle lobe and the lingula are most commonly affected
[7,
36,
42,
46,
47], any segment can be
involved [34,
40]. Other occasional findings
include consolidation and ground-glass opacities
[7,
30,
37,
38]. Atelectasis and
mediastinal adenopathy are uncommon
[5]. Recently it has been
suggested that the coexistence of bronchiectasis and bronchiolitis (i.e.,
centrilobular nodules and a mosaic pattern) is highly suggestive of
nontuberculous mycobacteria infection
[48] (Figs.
5A,
5B,
5C, and
5D).
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Fig. 6A —41-year-old man with AIDS, CD4 count of 166 cells/mL, and
viral load of 153,000 cells/mL, with cough and fever. Cultures of sputum and
histopathologic material obtained at mediastinal biopsy showed
Mycobacterium avium-intracellulare complex organisms. Biopsies were
negative for neoplasm. Frontal chest radiograph shows left-sided mediastinal
and upper lobe mass (arrow). Note also subtle left upper lobe
reticular opacities.
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Fig. 6B —41-year-old man with AIDS, CD4 count of 166 cells/mL, and
viral load of 153,000 cells/mL, with cough and fever. Cultures of sputum and
histopathologic material obtained at mediastinal biopsy showed
Mycobacterium avium-intracellulare complex organisms. Biopsies were
negative for neoplasm. Axial CT image (5-mm section, soft-tissue window
setting) shows bilateral paratracheal adenopathy (asterisks) and left
upper lobe invading mediastinum (arrows).
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Fig. 6C —41-year-old man with AIDS, CD4 count of 166 cells/mL, and
viral load of 153,000 cells/mL, with cough and fever. Cultures of sputum and
histopathologic material obtained at mediastinal biopsy showed
Mycobacterium avium-intracellulare complex organisms. Biopsies were
negative for neoplasm. Axial CT image (5-mm section, lung window setting)
obtained at more caudal level shows tree-in-bud opacities in superior segments
of both lower lobes (arrows).
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HIV Patients
Infection by nontuberculous mycobacteria in HIV-infected patients is
characterized by disseminated disease
[49]. MAC is the most common
nontuberculous mycobacteria agent identified in patients with AIDS and is
frequently cultured from blood, bone marrow, lung, liver, spleen, and lymph
nodes [9,
49]. During the 1990s, the
lifetime prevalence of the disease among homosexual men was near 30%
[50,
51]. MAC infection occurs in
the setting of low CD4 counts (usually < 100 cells/mm3)
[52]. The gastrointestinal
tract is thought to be the source of infection, with eventual dissemination by
bacteremia [52,
53]. The clinical picture
consists of systemic symptoms such as fever, weight loss, fatigue, abdominal
pain, and diarrhea. Lymphadenopathy and hepatosplenomegaly are common findings
on physical examination. The diagnosis is usually established by culture of
blood, bone marrow, or other sterile body site
[52].
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Fig. 7A —27-year-old man with AIDS and low CD4 count (< 40
cells/mL) treated with highly active antiretroviral therapy. Despite favorable
immune response, patient developed fever and back pain. Cultures of
histopathologic material obtained from retroperitoneal lymph node biopsy
showed Mycobacterium avium-intracellulare complex organisms. Frontal
chest radiograph shows bilateral bulky mediastinal lymphadenopathy. Clinical
and imaging findings are consistent in showing immune reconstitution syndrome.
Repeat radiographs after treatment (not shown) showed decreased mediastinal
adenopathy.
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Fig. 7B —27-year-old man with AIDS and low CD4 count (< 40
cells/mL) treated with highly active antiretroviral therapy. Despite favorable
immune response, patient developed fever and back pain. Cultures of
histopathologic material obtained from retroperitoneal lymph node biopsy
showed Mycobacterium avium-intracellulare complex organisms. Axial CT
image (5-mm section, soft-tissue window setting) obtained in upper abdomen
shows extensive retroperitoneal and mesenteric adenopathy
(asterisks).
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Fig. 8A —70-year-old asymptomatic man with pulmonary nodule found on
routine chest radiograph (not shown). Histopathologic analysis of resected
specimen showed granulomatous inflammation and no evidence of malignancy.
Cultures showed Mycobacterium avium-intracellulare complex organisms.
Axial CT image (3.75-mm section, lung window setting) (A) and fused
axial image from combined 18F-FDG PET/CT (B) show spiculated
right upper nodule with significant FDG uptake.
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Fig. 8B —70-year-old asymptomatic man with pulmonary nodule found on
routine chest radiograph (not shown). Histopathologic analysis of resected
specimen showed granulomatous inflammation and no evidence of malignancy.
Cultures showed Mycobacterium avium-intracellulare complex organisms.
Axial CT image (3.75-mm section, lung window setting) (A) and fused
axial image from combined 18F-FDG PET/CT (B) show spiculated
right upper nodule with significant FDG uptake.
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Because MAC infection frequently coexists with other pulmonary infections
(e.g., cytomegalovirus, pyogenic bacteria, Pneumocystis jiroveci, Candida
albicans, Cryptosporidium organisms, and so forth) or even neoplasms
(e.g., Kaposi sarcoma) [9,
49,
54,
55], pure radiographic
findings are difficult to determine. Cases with MAC infection and no
coexistent pulmonary infection are scant. In these reports, however,
mediastinal lymphadenopathy seems to be the most common manifestation, with
airspace opacities, miliary nodules, and pleural effusion reported
infrequently. Normal chest radiographic findings are not infrequent
[5,
49,
54,
55] (Figs.
6A,
6B, and
6C).
M. xenopi can also cause disseminated disease in patients with HIV
[56]. Radiologic findings
include heterogeneous peribronchial opacities, reticular opacities, miliary
nodules, cavitation, atelectasis, pleural thickening, and lymphadenopathy
[56,
57]. In patients with AIDS,
infection with M. kansasii tends to be confined to the lungs.
Reported radiographic findings include unifocal and unilateral alveolar
opacities, mediastinal and hilar adenopathy, cavitation, and pleural effusion
[58].
Recently, the immune reconstitution syndrome has been described in patients
with HIV weeks to months after starting highly active antiretroviral therapy.
This entity has been described with a variety of pathogens such as MAC,
tuberculosis, Cryptococcus neoformans, cytomegalovirus, P.
jiroveci, diverse viruses, and even inflammatory diseases such as
sarcoidosis [59]. The immune
reconstitution syndrome consists of an inflammatory response accompanied by
clinical deterioration related to a wide range of inflammatory reactions in
diverse organs directed against different preexisting microorganisms in
tissues [59]. Thoracic disease
manifests with cough or wheezing, fever, night sweats, dyspnea, weight loss,
and chest pain. Radiographic and CT findings include mediastinal and hilar
lymphadenopathy that may exhibit hypoattenuating centers, parenchymal
opacities, cavitation, nodules, endobronchial nodules, tree-in-bud opacities,
and pericardial effusion [60]
(Figs. 7A and
7B).
Non-HIV Immunocompromised Patients
Disseminated nontuberculous mycobacteria infection in the non-HIV
immunocompromised patient occurs in the setting of cytotoxic chemotherapy,
solid organ transplantation, chronic corticosteroid therapy, leukemia,
lymphoma, and so forth
[61-63].
Although MAC and M. kansasii appear to be the most common infecting
organisms, M. gordonae, Mycobacterium chelonei, and M.
fortuitum have also been implicated
[49,
61-63].
Clinical manifestations are nonspecific and include fever, weight loss, and
malaise [49]. The lungs and
the gastrointestinal tract appear to be the most likely source of disseminated
infection, with hematogenous spread a posteriori
[49]. Nontuberculous
mycobacteria are more frequently cultured in bone marrow, sputum or lung,
liver, spleen, and lymph nodes
[49,
61,
62]. Unfortunately, reports of
radiographic findings in this setting are limited and include reticular and
nodular opacities, cavities, and mediastinal and hilar adenopathy
[61,
63].
Nodules or Masses in Asymptomatic Patients
Pulmonary nontuberculous mycobacteria infection can manifest as nodules or
masses in asymptomatic patients
[64,
65] (Figs.
8A,
8B,
9A, and
9B). In a series of 20
patients with resected solitary pulmonary nodules caused by nontuberculous
mycobacteria, MAC was cultured in 12 (60%)
[66]. When multiple, nodules
are usually clustered together and have a uniform size, a somewhat helpful
feature for differentiation from malignancy. CT may show intralesional
calcification or increased attenuation suggestive of a granulomatous cause
[5,
14]. Both have
18F-FDG and 11C-choline focal uptake has been described
in these nodules [65,
67]; however, the degree of
uptake is usually less than that seen in cancer and tuberculosis
[65].
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Fig. 9A —42-year-old asymptomatic woman with multiple nodules found on
routine chest radiograph. Cultures of histopathologic material obtained by
fine-needle biopsy showed Mycobacterium xenopi organisms. Frontal
chest radiograph shows multiple bilateral pulmonary nodules.
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Fig. 9B —42-year-old asymptomatic woman with multiple nodules found on
routine chest radiograph. Cultures of histopathologic material obtained by
fine-needle biopsy showed Mycobacterium xenopi organisms. Axial CT
image (2-mm section, lung window setting) shows bilateral, irregularly
marginated nodules in both upper lobes.
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Fig. 10 —Young man with achalasia, fever, and cough. Culture of
bronchoalveolar lavage fluid was positive for Mycobacterium
fortuitum. Frontal chest radiograph shows dilated esophagus (white
arrows). Note cluster of small nodules in right upper lobe (black
arrows).
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Infection in Patients with Deglutition Problems
By the late 1990s, at least 20 cases of diffuse pulmonary infection caused
by rapidly growing mycobacteria in patients with esophageal motility disorders
had been reported [68]. M.
fortuitum and M. chelonae account for most isolates in this
setting. Associated esophageal disorders include achalasia, hiatal hernia,
dysmotility due to stroke or Parkinson's disease, and colonic interposition.
Infection may complicate areas of lipid pneumonia
[68]. The clinical
presentation frequently includes fever, cough, weight loss, night sweats,
hemoptysis, and dyspnea. Radiologic findings include unilateral or bilateral
heterogeneous reticulonodular or alveolar opacities without lobar
predominance. Pleural effusion was present in 20% and cavitary disease in 15%
of reported cases [68,
69]
(Fig. 10).
Hypersensitivity Pneumonitis
By 2005, at least 37 cases of hypersensitivity pneumonitis associated with
inhaled MAC, often from hot tub exposure, had been described
[22]. Affected patients
present with dyspnea, cough, and fever
[22]. Pulmonary function tests
show either an obstructive or a restrictive pattern, often with an impaired
diffusion capacity for carbon monoxide
[22]. Lung biopsies show
features of hypersensitivity pneumonitis and cultures frequently grow MAC.
However, whether this phenomenon represents true hypersensitivity pneumonitis
or infection remains controversial
[22,
70-74].
MAC has been shown to exist in natural sea water and in fresh water
[75,
76] and can become
concentrated in hot water systems
[77]. Water jets from hot tubs
are thought to promote aerosol formation of bacteria that eventually travel to
the lung by inhalation [71,
77]. Affected patients have
been treated with or without corticosteroids or antimycobacterial therapy with
equally good results if removal from the source of exposure (i.e., the hot
tub) is achieved [71,
72]. M. chelonae has
been associated with hypersensitivity pneumonitis among workers exposed to
metalworking fluid in the automotive industry
[78,
79].
Chest radiographs usually show abnormal findings, including diffuse fine
nodular and reticulonodular opacities, diffuse opacities, and areas of
consolidation. Characteristic CT findings include ill-defined, ground-glass
centrilobular nodules (Fig.
11), more diffuse ground-glass opacities, and air trapping on
expiratory examination [22,
80].
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Fig. 11 —Middle-aged man with cough, fever, and dyspnea who recently
purchased indoor hot tub. Histopathologic analysis of lung biopsy specimen
showed features of hypersensitivity pneumonitis; cultures of bronchoalveolar
lavage fluid showed Mycobacterium avium-intracellulare complex
organisms. Axial high-resolution CT image (1.25-mm section, lung window
setting) of chest shows diffusely distributed ground-glass nodules. Clinical,
imaging, and histopathologic features are consistent with "hot tub
lung."
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Conclusion
Pulmonary nontuberculous mycobacteria infection is an increasingly
important cause of morbidity and even mortality. The clinical and radiographic
manifestations of infection are variable and frequently overlap. Diagnosis may
be difficult and delayed, but consideration of nontuberculous mycobacteria
disease as a possible diagnosis is the first step toward making the correct
diagnosis and instituting appropriate treatment. Cooperation of pulmonary
physicians and radiologists is mandatory because fiberoptic bronchoscopy with
bronchoalveolar lavage or transbronchial lung biopsy is often the next most
appropriate step after radiologic imaging for securing a definitive
diagnosis.
APPENDIX 1: American Thoracic Society Criteria for Diagnosis of Pulmonary Nontuberculous Mycobacterial Infection (Adapted from [12])
Clinical Criteria
- Pulmonary symptoms with
- - Nodular or cavitary opacities on chest radiography, or
- - Multifocal bronchiectasis with multiple small nodules on high-resolution
CT
AND
- Appropriate exclusion of other diagnoses
Microbiologic Criteria
- Positive culture from at least two separate sputum samples
OR
- Positive culture from at least one bronchial wash or lavage
OR
- Transbronchial or other lung biopsy with mycobacterial features
(granulomatous inflammation or acid-fast bacillus) and positive for
nontuberculous mycobacteria or biopsy showing mycobacterial histopathologic
features (granulomatous inflammation or acid-fast bacillus) and one or more
sputum or bronchial washings that are culture-positive for nontuberculous
mycobacteria
Note:
- Expert consultation should be obtained when nontuberculous mycobacteria are
recovered that are either infrequently encountered or usually representative
of environmental contamination.
- Patients who are suspected of having nontuberculous mycobacteria lung
disease but do not meet the diagnostic criteria should be followed up until
the diagnosis is firmly established or excluded.
- Making the diagnosis of nontuberculous mycobacteria lung disease does not,
per se, necessitate the institution of therapy, which is a decision based on
the potential risks and benefits of therapy for the individual patient.
APPENDIX 2: Common Predisposing Conditions for Pulmonary Nontuberculous Mycobacterial Infection (Adapted from [6])
Underlying Lung Disease
- Chronic obstructive pulmonary disease
- Prior tuberculosis
- Prior chest surgery
- Lung carcinoma
- Interstitial lung disease
- Cystic fibrosis
Occupational Risk Factors
- Mining
- Welding
- Sandblasting
- Painting
Other
- Immune Deficiency
- Congenital
- AIDS
- Organ transplants
- Corticosteroid administration
- Achalasia
- Previous gastrectomy
- Renal failure, dialysis patients
- Scoliosis, pectus excavatum
- Collagen vascular disorders
- Advancing age
- Alcohol abuse
- Smoking
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Abstract
Introduction
