Epidemiology and clinical features
The incidence of pulmonary LCH (PLCH) is unknown. Reports provided by histopathological studies and interstitial lung diseases registries revealed about 5% of PLCH in this population [Tazi 2006]. Data from a Japanese survey show an estimated prevalence of 0.07-0.27/100000 population in females and males, respectively [Watanabe et al 2001]. The prevalence may be underestimated. Because of potential spontaneous remissions in asymptomatic patients the prevalence may generally be underestimated. This hypothesis is supported by the results of the recently wider use of chest high-resolution computed tomography (HRCT).
PLCH affects mainly young, predominantly smoking (> 90%) adults with a peak at 20-40 years of age and a slight predominance of women. It is unknown if there are any racial differences in this disease [Tazi 2006].
Patients with PLCH often present with a non-productive cough or dyspnea, but these symptoms are often insidious in onset and patients may attribute them to smoking. Associated unspecific symptoms like fatigue, weight loss, night sweats and fever may be observed [Tazi 2006; Vassallo et al 2002]. However, about 20% of patients with PLCH are initially asymptomatic.
About the same percentage of patients is diagnosed by acute symptoms of a pneumothorax. Hemoptysis is uncommon and should lead to rule out other causes, particularly lung cancer in these smoking patients. Physical examination of the chest is usually normal. Clubbing is exceedingly rare.