This disorder is characterized by an abnormal, non-neoplastic proliferation of histiocytes (histiocytosis X cell), or macrophages. These cells are morphologically similar to the Langerhans cells. Disease involvement may be localized to the lungs or may be more widespread and involve multiple organ systems to include the bones, lung, skin, and the pituitary gland. Primary pulmonary histiocytosis X refers to eosinophilic granuloma that is localized to the lung.

This disorder affects primarily young adults. Caucasians are affected more frequently than persons of African descent. One note of interest is that this disorder occurs primarily in persons who engage in cigarette smoking. The frequency of tobacco abuse among patients with EG is approximately 97%.

Symptoms include a nonproductive cough or exertional dyspnea, and less commonly, fever, weight loss, and fatigue. Pneumothorax occurs in 15% of affected individuals. Diabetes insipidus occurs when the pituitary is involved. Rarely, abnormalities on physical exam include rales or clubbing; however, most patients present with no pathologic findings.

Radiographic abnormalities include a reticular nodular infiltrate characteristically located in the upper lung zones and sparring the costophrenic angles. Honeycombing may be noted on radiographs in 50% of patients. Pleural effusions and hilar adenopathy are infrequent but may occur. As mentioned, pneumothorax may be noted, and in the proper setting, should clue the physician to the possibility of EG.

The disease course is variable. Many patients experience complete remission; however, other patients suffer progressive disease and develop respiratory insufficiency, cor pulmonale, or death. The mortality rate associated with this disease is 2 to 6%.

The diagnosis is established by open lung biopsy. Transbronchial biopsy is inadequate for diagnosis. Bronchoalveolar lavage may be useful as identification of X bodies within the histiocytosis X cells recovered may allow diagnosis.

Associated lab abnormalities are nonspecific. Pulmonary function testing abnormalities are variable.

The disorder is often self-limited and therefore therapy is often not necessary. Steroids have been associated with clearing of systemic symptoms. Therefore, any patient who appears to be deteriorating should probably receive steroid therapy.