# Late Diagnosis of Langerhans Cell Histiocytosis by Skin Biopsy in a Lung Transplant Candidate Patient

## TL;DR

A lung transplant candidate was diagnosed with Langerhans cell histiocytosis years after initial symptoms, highlighting the importance of considering this condition in similar cases.

## Contribution

The case emphasizes the need to systematically search for LCH in adults with unexplained bullous emphysema and associated clinical features.

## Key findings

- LCH was diagnosed via scalp skin biopsy in a patient initially thought to have bullous emphysema.
- The presence of diabetes insipidus and skin lesions should prompt consideration of LCH in adults with undiagnosed respiratory conditions.
- Skin biopsy is a valuable diagnostic tool for LCH in patients with atypical presentations.

## Abstract

We present the case of a lung transplant candidate under veno-venous membrane oxygenation assistance (VV ECMO) whose diagnosis of emphysema of undetermined etiology was redefined as Langerhans cell histiocytosis (LCH) due to a scalp skin biopsy performed years after the beginning of his respiratory symptoms. A 20-year-old patient started three years before his admission with progressive dyspnea leading to a diagnosis of bullous emphysema of undetermined cause, which evolved into respiratory failure and evaluation for bilateral lung transplant. Three years later, he developed bilateral pneumonia requiring mechanical ventilation. When refractory hypoxemia ensued, he had to be placed on VV ECMO. Under these conditions, he was transferred to our center and listed for a bilateral pulmonary transplantation. Forty-eight hours after admission, and due to intense polyuria, central diabetes insipidus was diagnosed. In this clinical context, the presence of cutaneous lesions on the scalp was reconsidered and biopsied under the presumption of possible LCH, with pathology analysis confirming the diagnosis. He continued to be assisted with VV ECMO for 66 more days as a bridge to transplantation, developing multi-organ failure and passing away before a donor organ was available. The diagnosis of LCH should be considered in any adult patient with bullous emphysema of undetermined cause. Given the possibility of early therapeutic interventions, the search for its clinical associations (e.g., diabetes insipidus and/or skin lesions) should be a systematic part of the etiologic workup. The availability of skin specimens to reach a diagnosis makes its thorough search an important part of the diagnostic approach.