PULMONARY LANGERHANS CELL HISTIOCYTOSIS
Pulmonary Langerhans cell histiocytosis (PLCH) of the lung primarily affects young adults between the ages of 20 to 40 years. Whites are affected more commonly than individuals of African or Asian descent. The pathogenesis of PLCH is unknown. The near universal association of PLCH with cigarette smoking strongly implies a causative role.
The clinical presentation is variable, from an
asymptomatic state (16%) to a rapidly progressive condition. The duration of
illness is usually less than 1 year before diagnosis. The most common clinical
manifestations at presentation are cough (56%-70%), dyspnea (40%- 87%), chest
pain that is frequently pleuritic (10%-21%), fatigue (30%), weight loss
(20%-30%), and fever (15%). Pneumothorax occurs in about 25% of patients and is
occasionally the first manifestation of the illness. Pulmonary hypertension is
common. Hemoptysis occurs in approximately 13% of cases and should prompt
consideration of superimposed infection or malignancy. In addition, diabetes
insipidus, secondary to hypothalamic involvement, may be present in
approximately 15% of patients and is believed to portend a worse prognosis.
Cystic bone lesions are present in 4% to 20% of patients and may produce
localized pain or a pathologic bone fracture. The physical examination findings
are usually normal. Routine laboratory studies are nonspecific.
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The radiographic features vary depending on the stage of the disease. The
combination of ill-defined or stellate nodules (2-10 mm in size), reticular or
nodular opacities, upper zone cysts or honeycombing, preservation of lung
volume, and costophrenic angle sparing are highly specific for PLCH.
High-resolution computed tomography (HRCT) lung scanning that reveals the
combination of nodules and thin-walled cysts with a mid to upper zone
predominance and interstitial thickening in a young smoker is so characteristic
that it can be diagnostic of PLCH. Serial chest CT scanning suggests a sequence
of progression from nodules to cavitating nodules to cystic lesions.
Physiologically, the most prominent and frequent
pulmonary function abnormality is a markedly reduced DLCO (diffusing capacity
for carbon monoxide), but varying degrees of restrictive disease, airflow
limitation, and diminished exercise capacity are described. Whereas
predominantly nodular disease is usually associated with normal or restrictive
pulmonary function tests, cystic disease is more likely to be associated with
airflow limitation and hyperinflation. Limitations in activity and exercise
intolerance out of proportion to pulmonary function abnormalities are commonly
present. Gas exchange abnormalities, reflected by a worsening alveolar–arterial
oxygen difference with increasing exercise, are seen in the majority of
patients.
The finding of more than 5% Langerhans cells on bronchoalveolar lavage strongly
suggests the diagnosis of PLCH. Transbronchial biopsy can be sufficient to make
the diagnosis; however, a substantial number of false-negative or nondiagnostic
biopsies may result from sampling error and insufficient tissue. Video
thoracoscopic lung biopsy is generally definitive. Langerhans cells can be recognized by their
characteristic staining for S-100 protein. Tissue immunostaining with the
monoclonal antibody OKT-6 (CD1a) distinguishes Langerhans cells from other
histiocytes and can be a useful adjunct in difficult cases. These cells also
demonstrate staining with the monoclonal antibody MT-1.
Smoking cessation is the key treatment, resulting in
clinical improvement in many subjects. Immunosuppressive therapies (i.e.,
glucocorticoids and cytotoxic agents) are of limited value. Lung
transplantation should be considered in patients with advanced disease.
Recurrence of the condition in the transplanted lung may occur. Estimated 5-
and 10-year survival rates are 74% and 64%, respectively. Respiratory failure
is the most common cause of death. The other major cause of death is malignancy, primarily of hematologic or epithelial origin.
