Recurrent pneumothoraces, rash, and polyuria

The Histiocyte Society has developed a simplified classification system for adult Langerhans' cell histiocytosis, consisting of single organ and multisystem involvement.1 The incidence in adults is around 1-2 cases per million with a mean age at diagnosis of 35 years.1 Up to a quarter of cases are asymptomatic.2,3 Presenting symptoms depend on the pattern of organ involvement, with bony pain, weight loss, and fever being the most common.1 Diabetes insipidus from pituitary involvement is a characteristic manifestation of the disease-as in our patient. Smoking cessation is essential in pulmonary Langerhans' cell histiocytosis.4 Single organ disease can be managed with watchful waiting; multisystem disease may respond to corticosteroids and systemic chemotherapy.2,3,5 Most patients experience a favourable outcome, although isolated pulmonary Langerhans' cell histiocytosis has the worst outcome.1 Lung transplant can be considered in advanced disease, but there may be recurrence in the allograft.2,3 Diagnosis of Langerhans' cell histiocytosis is often delayed with a median time of 4 months.1 There was substantial delay in diagnosis in our patient, confirming suboptimal awareness for this uncommon condition.