Disease: Pulmonary Histiocytosis X
Clinical Information:
This 42 year old Caucasian male had a 2-year history of
non-productive cough, dyspnea on exertion, and fatigue. He
had four episodes of fever in the preceding 18 months. He had
a 40 pack-year history of smoking. He was an airline pilot
with no relevant past medical history, family history,
occupational or domestic antigen exposures. Pulmonary
function testing revealed a mild restrictive pattern.
Imaging:
His CXR shows a bilateral, predominantly mid-
and upper-zone reticulonodular pattern with some small cystic
areas in the upper lobes. There is mild bilateral hilar
adenopathy.
Conventional and high resolution CT reveal
multiple small nodules thin-walled, irregular cysts
predominantly in the upper 1/3 of the lungs.
Discussion:
The combination of nodules and multiple, irregular-shaped,
thin-walled cysts is highly suggestive of Pulmonary
Histiocytosis X(also known as Pulmonary Eosinophilic
Granulmona.This condition of unknown etiology is uncommon,
occurring predominantly in smokers ( >90%) with mean age at
presentation of 32 years. Patients may be asymptomatic
(approx. 25%), or have non-specific respiratory symptoms .
Pneumothorax is the presenting feature in up to 20%.
Constitutional symptoms of fever, weight loss and fatigue
may be present. Hemoptysis is rare, as is bone involvement in
patients with pulmonary manifestations. Pulmonary function
tests are non-diagnostic with normal, restrictive,
obstructive, or mixed patterns all seen. Variable clinical
course with spontaneous remissions and 2-6 % mortality.
Presentation at extremes of age, multi-organ involvement, low
diffusion capacity and recurrent pneumothoraces are
independent poor prognostic indicators. Treatment is largely
symptomatic.
Differential Diagnosis (DDx):
The recognized features of Pulmonary Histiocytosis X are 1-
5mm nodules and multiple thin-walled cysts which tend to
coalesce to form bizarre shapes in a
centrilobular/peribronchiolar distribution with an upper lung
predominance. Intervening lung is often normal. Less
commonly one may see cavitation in larger nodules,
lymphadenopathy, ground-glass opacity or fine reticular
opacity.
True lung cysts need to be distinguished from emphysematous
blebs / bullae ( no visible walls), dilated airways
(continuity and elongation of dilated airways on contiguous
slices) and pneumatoceles.
The differential for true lung cysts lies between
Histiocytosis X, Lymphangiomyomatosis (L.A.M.)and Tuberous
sclerosis (T.S.). HRCT features may be identical in these
patients. Helpful differentiating features are nodules and
bizarre-shaped cysts with an upper lung predominance in
Histiocytosis X, while LAM is associated with chylous
effusions, female of child-bearing age, and more uniformly
shaped cysts in a diffuse distribution. TS lung disease
appears very similar to LAM but can be seen in males.
End-stage Idiopathic pulmonary fibrosis may occasionally
cause confusion with extensive basal and subpleural
honeycombing but the intervening lung is abnormal and
fibrotic. In Histiocytosis X and LAM, the intervening lung
is usually normal.
References:
Soler P. et al. Pulmonary Langherans' Cell Granulomatosis.
Annu. Rev. Med. 1992;105-115.
Schonfield N. et al. Clinical and Radiographic Features, Lung
Function and Therapeutic Results in Pulmonary Histiocytosis
X. Respiration.1993; 60: 38-44.
Moore AD et al. Pulmonary Histiocytosis X: comparison of
radiographic and CT findings. Radiology. 172(1) : 249-54,
1989 July.
Brauner MW et al. Pulmonary Histiocytosis X : evaluation
with high-resolution CT. Radiology . 172 (1) : 255-8, 1989
Jul.
Case contributed by Martin O'Driscoll, MB and Debra Dyer,
MD.
Debra Dyer, MD
