The histiocytoses are rare disorders characterized by the accumulation of macrophage, dendritic cell, or monocyte-derived cells in various tissues and organs of children and adults. More than 100 different subtypes have been described, with a wide range of clinical manifestations, presentations, and histologies. Since the first classification in 1987, a number of new findings regarding the cellular origins, molecular pathology, and clinical features of histiocytic disorders have been identified. We propose herein a revision of the classification of histiocytoses based on histology, phenotype, molecular alterations, and clinical and imaging characteristics. This revised classification system consists of 5 groups of diseases: (1) Langerhans-related, (2) cutaneous and mucocutaneous, and (3) malignant histiocytoses as well as (4) Rosai-Dorfman disease and (5) hemophagocytic lymphohistiocytosis and macrophage activation syndrome. Herein, we provide guidelines and recommendations for diagnoses of these disorders.

; for the CORIMUNO-19 Collaborative Group IMPORTANCE Severe pneumonia with hyperinflammation and elevated interleukin-6 is a common presentation of coronavirus disease 2019 (COVID-19). OBJECTIVE To determine whether tocilizumab (TCZ) improves outcomes of patients hospitalized with moderate-to-severe COVID-19 pneumonia. DESIGN, SETTING, AND PARTICPANTS This cohort-embedded, investigator-initiated, multicenter, open-label, bayesian randomized clinical trial investigating patients with COVID-19 and moderate or severe pneumonia requiring at least 3 L/min of oxygen but without ventilation or admission to the intensive care unit was conducted between March 31, 2020, to April 18, 2020, with follow-up through 28 days. Patients were recruited from 9 university hospitals in France. Analyses were performed on an intention-to-treat basis with no correction for multiplicity for secondary outcomes. INTERVENTIONS Patients were randomly assigned to receive TCZ, 8 mg/kg, intravenously plus usual care on day 1 and on day 3 if clinically indicated (TCZ group) or to receive usual care alone (UC group). Usual care included antibiotic agents, antiviral agents, corticosteroids, vasopressor support, and anticoagulants. MAIN OUTCOMES AND MEASURES Primary outcomes were scores higher than 5 on the World Health Organization 10-point Clinical Progression Scale (WHO-CPS) on day 4 and survival without need of ventilation (including noninvasive ventilation) at day 14. Secondary outcomes were clinical status assessed with the WHO-CPS scores at day 7 and day 14, overall survival, time to discharge, time to oxygen supply independency, biological factors such as C-reactive protein level, and adverse events. RESULTS Of 131 patients, 64 patients were randomly assigned to the TCZ group and 67 to UC group; 1 patient in the TCZ group withdrew consent and was not included in the analysis. Of the 130 patients, 42 were women (32%), and median (interquartile range) age was 64 (57.1-74.3) years. In the TCZ group, 12 patients had a WHO-CPS score greater than 5 at day 4 vs 19 in the UC group (median posterior absolute risk difference [ARD] −9.0%; 90% credible interval [CrI], −21.0 to 3.1), with a posterior probability of negative ARD of 89.0% not achieving the 95% predefined efficacy threshold. At day 14, 12% (95% CI −28% to 4%) fewer patients needed noninvasive ventilation (NIV) or mechanical ventilation (MV) or died in the TCZ group than in the UC group (24% vs 36%, median posterior hazard ratio [HR] 0.58; 90% CrI, 0.33-1.00), with a posterior probability of HR less than 1 of 95.0%, achieving the predefined efficacy threshold. The HR for MV or death was 0.58 (90% CrI, 0.30 to 1.09). At day 28, 7 patients had died in the TCZ group and 8 in the UC group (adjusted HR, 0.92; 95% CI 0.33-2.53). Serious adverse events occurred in 20 (32%) patients in the TCZ group and 29 (43%) in the UC group (P = .21). CONCLUSIONS AND RELEVANCE In this randomized clinical trial of patients with COVID-19 and pneumonia requiring oxygen support but not admitted to the intensive care...

Langerhans Cell Histiocytosis (LCH) is an orphan disease of clonal dendritic cells which may affect any organ of the body. Most of the knowledge about the diagnosis and therapy is based on pedriatic studies. Adult LCH patients are often evaluated by physicians who focus on only the most obviously affected organ without sufficient evaluation of other systems, resulting in patients being underdiagnosed and/or incompletely staged. Furthermore they may be treated with pediatric-based therapies which are less effective and sometimes more toxic for adults. The published literature on adult LCH cases lacks a comprehensive discussion on the differences between pediatric and adult patients and there are no recommendations for evaluation and comparative therapies. In order to fill this void, a number of experts in this field cooperated to develop the first recommendations for management of adult patients with LCH. Key questions were selected according to the clinical relevance focusing on diagnostic work up, therapy, and follow up. Based on the available literature up to December 2012, recommendations were established, drafts were commented by the entire group, and redrafted by the executive editor. The quality of evidence of the recommendations is predominantly attributed to the level of expert opinion. Final agreement was by consensus.

Adult pulmonary Langerhans' cell histiocytosis is a rare disorder of unknown aetiology that occurs predominantly in young smokers, with an incidence peak at 20-40 yrs of age. In adults, pulmonary involvement with Langerhans' cell histiocytosis usually occurs as a single-system disease and is characterised by focal Langerhans' cell granulomas infiltrating and destroying distal bronchioles.High-resolution computed tomography (HRCT) of the chest is essential to the diagnosis, typically showing a combination of nodules, cavitated nodules, and thick-and thin-walled cysts. A high macrophage count in bronchoalveolar lavage (BAL) fluid is a common but nonspecific finding that merely reflects exposure to tobacco smoke. BAL is useful for eliminating infections and the other infiltrating lung disorders that can be seen in young adults. Langerhans' cells can be identified in BAL fluid, but, in contrast to what was initially hoped, this test shows a very low sensitivity and is rarely useful in the diagnosis of the disease.The definite diagnosis of pulmonary Langerhans' cell histiocytosis requires identification of Langerhans' cell granulomas, which is usually achieved by surgical lung biopsy at a site selected by chest HRCT. In practice, however, lung biopsy is performed on a case-by-case basis.No effective treatment is available to date, and improved understanding of the mechanisms involved in the pathogenesis of pulmonary Langerhans' cell histiocytosis is urgently needed, and should help in the development of specific therapeutic strategies for patients with this orphan disease.

Acute respiratory failure (ARF) in patients with cancer is frequently a fatal event. To identify factors associated with survival of cancer patients admitted to an intensive care unit (ICU) for ARF, we conducted a prospective 5-year observational study in a medical ICU in a teaching hospital in Paris, France. The patients were 203 cancer patients with ARF mainly due to infectious pneumonia (58%), but also noninfectious pneumonia (9%), congestive heart failure (12%), and no identifiable cause (21%). We measured clinical characteristics and ICU and hospital mortality rates.ICU mortality was 44.8% and hospital mortality was 47.8%. Noninvasive mechanical ventilation was used in 79 (39%) patients and conventional mechanical ventilation in 114 (56%), the mortality rates being 48.1% and 75.4%, respectively. Among the 14 patients with late noninvasive mechanical ventilation failure (>48 hours), only 1 survived. The mortality rate was 100% in the 19 noncardiac patients in whom conventional mechanical ventilation was started after 72 hours. By multivariable analysis, factors associated with increased mortality were documented invasive aspergillosis (odds ratio [OR], 2.13; 95% confidence intervals [CI], 1.05-14.74), no definite diagnosis (OR, 3.85; 95% CI, 1.26-11.70), vasopressors (OR, 3.19; 95% CI, 1.28-7.95), first-line conventional mechanical ventilation (OR, 8.75; 95% CI, 2.35-35.24), conventional mechanical ventilation after noninvasive mechanical ventilation failure (OR, 17.46; 95% CI, 5.04-60.52), and late noninvasive mechanical ventilation failure (OR, 10.64; 95% CI, 1.05-107.83). Hospital mortality was lower in patients with cardiac pulmonary edema (OR, 0.16; 95% CI, 0.03-0.72). Survival gains achieved in critically ill cancer patients in recent years extend to patients requiring ventilatory assistance. The impact of conventional mechanical ventilation on survival depends on the time from ICU admission to conventional mechanical ventilation and on the patient's response to noninvasive mechanical ventilation.