Limited Utility of Chemotherapy for Pulmonary Langerhans Cell Histiocytosis Due to Unclear Diagnostic Criteria.

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare interstitial lung disease that affects young adults and is typically misdiagnosed or presents concurrently with more common respiratory conditions such as asthma or chronic obstructive lung disease (COPD). A combination of imaging, tissue biopsy, and clinical presentation is used for diagnosis since no definitive criteria have been established. Current standards are based on vague descriptors such as clustering of histologic markers but lack quantitative analysis. In this case report, we present a patient who was initially diagnosed with PLCH, but the lack of unanimity for diagnostic requirements led to conflicting diagnoses between institutions which may have prevented optimal care for the patient. The disparity limited new, alternative therapies for our patient that may have been beneficial since he was clinically not improving with smoking cessation and standard of care for obstructive lung diseases. However, quantitative endorsements for tissue analysis, such as requiring more than 30 Cd-1a stained Langerhans cells per high power field (HPF), may reduce discrepancies associated with current techniques. It is imperative that clear standards are established due to the unique treatment these patients require that is atypical from other pulmonary diseases such as asthma and COPD. New chemotherapeutic regimens such as cladribine and vemurafenib require oncologic care and have more broad side effects than typical pulmonary treatments, which emphasize the need for accurate diagnoses before starting treatment. Existing standards have created circumstances where PLCH is a differential but cannot be ruled out due to unclear criteria and limited research.