Roentgen Ray 1997

uhrad.com - Chest Imaging Case of the Day

Case #4

by: Robert Gilkeson, M.D.
John Hsu, M.D.

Diagnosis: Histiocytosis X.

Fig 4A: PA chest radiograph demonstrates
a left sided chest tube and pneumothorax.
The lungs are hyperinflated, with numerous
thin walled cysts throughout the lung.

   

Fig 4B & 4C: High resolution CT scan shows large, somewhat irregular cysts replacing much of the upper lobe lung parenchyma. Lower images show relative sparing of the lower lobes.

Discussion: An 18 year old male was admitted to the hospital with shortness of breath and chest pain. An outside chest radiograph showed a large left sided pneumothorax. The patient's history was remarkable only for a history of "asthma" treated symptomatically with aerosol treatments. He had previously been well and had played basketball without problems days before his admission to the hospital. He denied IV drug use or cigarette smoking, but admitted to daily marijauna use for five years prior to admission to the hospital. A chest radiograph following admission (Fig. 4A) showed a left sided chest tube, a small residual left sided pneumothorax, and subcutaneous emphysema. Closer evaluation showed hyperexpansion, and multiple thin walled cystic structures thoughout the lungs. Pulmonary function tests showed severe obstructive disease, with FEV1 17% of predicted. A high resolution chest CT (HRCT) confirmed the presence of multiple, thin walled cysts (Fig 4A-4B). These cysts were confluent in the upper lobes, with relative sparing of the base of the lung. There were no significant parenchymal nodules, no adenopathy or pleural disease. A biopsy was performed that showed extensive fibrosis, and the presence of Langerhans cells, consistent with advanced pulmonary histiocytosis X.

Histiocytosis X encompasses a wide range of presentations and severity, all based on the abnormal proliferation of histocytes. Letterer-Siwe disease, a pediatric multisystem disease with a 70% mortality rate presents with diffuse histiocytic infiltration of liver, spleen, skin and bone. Hans Schuller Christian disease is the chronic disseminated form, and often presents with the classic triad of diabetes insipidus, exopthalmos, and lytic skull lesions. Pulmonary histiocytosis X, or eosinophilic granuloma of the lung, is characterized by infiltration of the lung by histiocytes. Early involvement shows histiocytic proliferation at the level of the bronchioles and alveolar ducts. These nodules can cavitate, and may cause bronchiolar obstruction. The "stellate " appearance of these nodules in a centrilobular distribution is felt to be characterisitc of the disease. By electron microscopy, the "racket shaped" Birbeck granules can be seen in the cytoplasm of the histiocyte cell. This finding, in conjunction with positive staining for the protein S-100, is felt to be virtually pathognomonic of pulmonary histiocytosis X.[1]

Pulmonary histiocytosis X usually presents in the third to fourth decade. It is a rare cause of interstitial lung disease, occurring in 3% patients who underwent lung biopsy for chronic infiltrative lung disease.[2] It is rare in blacks, and is seen equally in males and females. Young males appear to have the worst prognosis. Most series show that between 90-95% of patients smoke, and symptoms often improve with smoking cessation.[3] Patients are generally symptomatic, and present with cough, dyspnea and chest pain.[3] Long term follow up however shows remission in 30%, while 30% stabilize, and 30% progress to end stage lung disease. Between 15-25% will present with spontaneous pneumothorax. Pulmonary function tests will classically show a decrease DLCO, and while many demonstrate purely restrictive physiology on pulmonary function tests, patients can present with severe obstructive lung disease.

Radiographically, pulmonary histiocytosis X presents with a diffuse, reticulonodular pattern. There appears to be a slight upper lobe predominance, with sparing of the costophrenic angles. Chest radiographs generally show a combination of nodules and cysts. The reticular pattern classically described often represents the walls of these thin walled cysts. Nodules are usually 2-5mm in size, and the cysts generally measure less than 1cm. in diameter[4]. While some series describe mediastinal lymphadenopathy [5], it is uncommon in most series. Though pneumothorax is common, pleural effusions are rare in pulmonary histiocytosis X.

High resolution CT can be diagnostic. In a series by Brauner et al., cysts were found to be the most common finding. Nodules were generally seen in conjunction with these cysts, and cavitation was relatively uncommon.[6] Morphologic evaluation of the cysts can sometimes help differentiate pulmonary histiocytosis X from three other important differential considerations: lymphangiomyomatosis (LAM), emphysema, and cystic bronchiectasis. The cysts in pulmonary histiocytosis X tend to be somewhat more irregular in contour, and unlike LAM, tend to have an upper lobe predominance. Recognition of these features are important in establishing the diagnosis and further treatment of this rare disorder.

References:
1. Colby TV,Miscellaneous Conditions and Lung Disease of Unknown Origin
In Spencer's Pathology of the Lung, Haselton PS,Ed.,1996,
McGraw-Hill, New York, pg 767-772.

2. Gaensler EA, Carrington CB. Open biopsy for chronic diffuse infiltrative lung
disease:clinical roentgenographic and physiologic correlations in 502 patients. Ann
Thorac Surg 1980;30:411-426.

3. Friedman PJ, Liebow AA, Sokoloff J. Eosinophilic granuloma of lung: clinical aspects
of primary pulmonary histiocytosis in the adult. Medicine 1981; 60:385-396.

4. Moore ADA, Godwin JD, Muller NL, et al. Pulmonary Histiocytosis X:Comparision of Radiographic
and CT Findings. Radiology 1989;172:249-254.

5. Weber, WN, Margolin FR, Nielsen SI. Pulmonary Histiocytosis X. Radiology
1969 107:280-289.

6. Brauner MW, Grenier, P, Mouelhi MM, et al. Pulmonary histiocytosis X: evaluation
with high-resolution CT. Radiology 1989;172:255-258.

Return to Day #5

Submitted by:
Robert C. Gilkeson, M.D.
John Hsu, M.D.