Langerhans cell histiocytosis (LCH) can affect children and adults with wide variety of clinical manifestations, including unifocal, single-system multifocal, single-system pulmonary (smoking-associated), or multisystem disease. The existing paradigms in the management of LCH in adults are mostly derived from the pediatric literature. Over the last decade, the discovery of clonality and MAPK-ERK pathway mutations in most cases led to the recognition of LCH as a hematopoietic neoplasm, opening the doors for treatment with targeted therapies. These advances have necessitated an update of the existing recommendations for the diagnosis and treatment of LCH in adults. This document presents consensus recommendations that resulted from the discussions at the annual Histiocyte Society meeting in 2019, encompassing clinical features, classification, diagnostic criteria, treatment algorithm, and response assessment for adults with LCH. The recommendations favor the use of 18F-Fluorodeoxyglucose positron emission tomography based imaging for staging and response assessment in majority of cases. Most adults with unifocal disease may be cured by local therapies, while the first-line treatment for single-system pulmonary LCH remains smoking cessation. Among patients not amenable or unresponsive to these treatments and/or have multifocal and multisystem disease, systemic treatments are recommended. Preferred systemic treatments in adults with LCH include cladribine or cytarabine, with emerging role of targeted (BRAF- and MEK-inhibitor) therapies. Despite documented response to treatments, many patients struggle with high symptom burden from pain, fatigue, and mood disorders that should be acknowledged and managed appropriately.

POEMS syndrome is a rare clonal plasma cell disease. Patients with POEMS syndrome are at risk of developing pulmonary hypertension, but the data on its incidence and impact on outcome are limited. We reviewed records of 154 POEMS syndrome patients with complete duplex echocardiography data for estimation of pulmonary artery systolic pressure (sPAP) at the time of diagnosis. Forty-two (27%) of 154 patients with pulmonary hypertension (estimated sPAP ≥50mmHg) were identified. Median age was 46 years (range 31-71 years). Patients with pulmonary hypertension were more likely to have peripheral edema (P=0.04), ascites (P=0.02), pleural effusion (P=0.005), and have longer time from onset to diagnosis (P=0.004) when compared with those without pulmonary hypertension. Restrictive abnormalities and decreased diffusion capacity of carbon monoxide were observed in 83% and 96% patients with pulmonary hypertension, compared with 50% and 72% in patients without pulmonary hypertension, respectively. Reversibility of pulmonary hypertension was observed after treatment of POEMS syndrome. After median follow of 32 months, survival of patients with pulmonary hypertension was worse than those without (median overall survival 54 months vs. median not reached, P=0.021). In conclusion, pulmonary hypertension is a common feature of POEMS syndrome, and is associated with signs of extravascular volume overload. Although active treatment of POEMS syndrome can reverse pulmonary hypertension, survival of these patients is worse than those without pulmonary hypertension.

POEMS syndrome is a rare plasma cell dyscrasia. This study compared the responses to and survival of 347 POEMS syndrome patients given three first-line treatment regimens: autologous stem cell transplantation (ASCT, N = 165) and melphalan + dexamethasone (MDex, N = 79), or lenalidomide + dexamethasone (LDex, N = 103). After a median 45-month follow-up, overall hematologic complete remission (CRH) was 46.4%, vascular endothelial growth factor complete remission (CRV) was 55.1%, and neurological remission (RN) was 93.8%. CRH was better with ASCT (49.7%) than with MDex (37.7%, p = 0.001). CRV was better with ASCT (66.2%) than with MDex (38.5%, p = 0.001) or LDex (47.7%, p = 0.008). Differences in RN achieved by three regimens (91.5% vs. 100% vs. 93.8%, p = 0.234) were not significant. Overall 3-year progression-free survival (PFS) was 80.5% and overall 3-year overall survival (OS) was 90.8%. PFS was 87.6% with ASCT and 64.9% with LDex (p = 0.003). OS in the three regimens did not differ (p = 0.079). In medium-high risk patients, ASCT had better CRH and CRV than MDex, and better PFS than LDex. Therefore, although all three treatments had reasonable responses and survivals, patients with higher risk may benefit more from ASCT treatment.