High prevalence of BRAFV600E in patients with cholestasis, sclerosing cholangitis or liver fibrosis secondary to Langerhans cell histiocytosis.

Targeted therapies with MAPK inhibitors have proven to modulate the clinical manifestations of patients with Langerhans cell histiocytosis (LCH). We explored the presence of BRAFV600E mutation in our cohort of patients with LCH and cholestasis, sclerosing cholangitis, or liver fibrosis that presented resistance to chemotherapy. The BRAFV600E mutation was detected either in the diagnosis (skin and bone) or liver biopsy in our cohort of 13 patients. Thus, we observed a high incidence of BRAFV600E mutation in 100% either in diagnostic biopsy (skin and bone) or liver biopsy in patients with progressive liver disease, sequela, or liver transplant requirement.

Langerhans cell histiocytosis in a young patient with Pitt-Hopkins syndrome.

Pitt-Hopkins syndrome (PTHS, MIM #610954) is a rare neurodevelopmental disease characterized by the association of intellectual disability, characteristic facial gestalt and episodes of abnormal and irregular breathing. PTHS is due to heterozygous loss-of-function variants in the TCF4 gene (transcription factor 4, MIM #602272) encoding for a basic helix-loop-helix transcription factor. TCF4 is highly expressed during early development of the nervous system, and it is involved in cellular differentiation and proliferation. Since the first clinical description in 1978, less than 200 PTHS patients have been described. A comprehensive phenotype, especially regarding cancer predisposition, is not yet well defined. We report the case of a 7-year-old boy affected by PTHS with a 4-week history of progressive swelling of the frontal bones diagnosed with Langerhans cell histiocytosis.

Post-scabietic nodules: Mimicker of infantile indeterminate cell histiocytosis and potential diagnostic pitfall.

Indeterminate cell histiocytosis (ICH) is an extremely rare disease and little is known about its etiology. Patients usually present with nodular, dermal proliferations of indeterminate cells, which characteristically resemble Langerhans cells but lack Birbeck granules. The clinical course is highly variable, ranging from spontaneous regression to rapid progression with reports of extracutaneous involvement, subsequent acute myeloid leukemias, and associated B-cell lymphomas. Rare cases of ICH-like reactions have been reported in the setting of scabies infestations as well as in patients who had been bitten by ticks and mosquitos. We present a successfully treated case of indeterminate cell-rich post scabietic nodules in an otherwise healthy 8-month-old boy and review the literature on similar cases. Clinical context is essential for correct interpretation of these indolent ICH-mimicking lesions, and to avert unnecessary patient anxiety and aggressive management.

Pulmonary Langerhans Cell Histiocytosis.

Pulmonary Langerhans cell histiocytosis (PLCH) is a diffuse cystic lung disease that is strongly associated with exposure to cigarette smoke. Recently, activating pathogenic mutations in the mitogen-activated protein kinase pathway have been described in the dendritic cells in patients with PLCH and have firmly established PLCH to be an inflammatory myeloid neoplasm. Disease course and prognosis in PLCH are highly variable among individual patients, ranging from spontaneous resolution to development of pulmonary hypertension and progression to terminal respiratory failure. A subset of patients with PLCH may have extrapulmonary involvement, typically involving the skeletal system in the form of lytic lesions, skin lesions, or the central nervous system most commonly manifesting in the form of diabetes insipidus. Smoking cessation is the cornerstone of treatment in patients with PLCH and can lead to disease regression or stabilization in a substantial proportion of patients. Further insight into the underlying molecular pathogenesis of PLCH has paved the way for the future development of disease-specific biomarkers and targeted treatment options directed against the central disease-driving mutations.

Pediatric Langerhans cell histiocytosis: state of the science and future directions.

Langerhans cell histiocytosis (LCH) is an inflammatory neoplasm of myeloid origin characterized by the presence of classic CD1a+/CD207+ cells. An ongoing debate over the grouping of LCH was finally settled in favor of neoplasm after the discovery of the BRAF V600E mutation in 2010. The pathologic cells were found to involve an almost universal activation of the MAPK/ERK pathway, with mutations identified in most kinases upstream of ERK (RAS/RAF/MEK). The clinical presentation of LCH is a mixed bag, ranging from self-resolving localized disease to fulminant, fatal disseminated disease. The current standard of care for patients with multisystem LCH, who have high relapse rates, continues to be combination treatment with vinblastine and prednisone. Patients treated with BRAF and MEK inhibitors have shown a significant and sustained response in early-phase trials. During the current decade, researchers have described an extensive genomic landscape for LCH that has significantly enlarged our understanding of the biology and pathogenesis of this disease, especially neurodegenerative LCH. These advances have opened the door to studies of precision medicine and targeted therapy in LCH. Disease reactivation, long-term sequelae, very high-risk disease, and neurodegenerative LCH represent ongoing challenges. A renewed understanding of the biology of this disease, coupled with targeted therapies, may help in overcoming most of these challenges.

Histiocytoses: emerging neoplasia behind inflammation.

Histiocytoses are disorders characterised by inflammation and the accumulation of cells derived from the monocyte and macrophage lineages, which results in tissue damage. Although they are often considered rare disorders with protean clinical manifestations, considerable advances in the understanding of their genetics have led to increased clinical recognition of these conditions, and fuelled further insights into their pathogenesis. In this Review, we describe insights into the cells of origin, molecular pathology, clinical features, and treatment strategies for some of the most common histiocytic disorders, including Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease. With the discovery of recurrent mutations affecting the mitogen-activated protein kinase and mTOR-AKT pathways in some of these histiocytoses, our understanding of these diseases has now evolved from the concept of a primary inflammatory condition to that of a clonal neoplastic disease. This understanding has led to the development of effective mechanism-based therapeutic strategies for patients with histiocytic diseases.

Current understanding and management of pulmonary Langerhans cell histiocytosis.

Pulmonary Langerhans cell histiocytosis (PLCH) is a diffuse lung disease that usually affects young adult smokers. PLCH affects different lung compartments; bronchiolar, interstitial and pulmonary vascular dysfunction may coexist to varying extents, resulting in diverse phenotypes. Analyses of PLCH tissues have identified activating mutations of specific mitogen-activated protein kinases (BRAFV600E and others). The current consensus is that PLCH represents a myeloid neoplasm with inflammatory properties: the myeloid tumour cells exhibit surface CD1a expression and up to 50% of the cells harbour activating BRAF or other MAPK mutations. PLCH may be associated with multisystem disease. The detection of disease outside of the thorax is facilitated by whole body positron emission tomography. The natural history of PLCH is unpredictable. In some patients, disease may remit or stabilise following smoking cessation. Others develop progressive lung disease, often associated with evidence of airflow limitation and pulmonary vascular dysfunction. Due to the inability to accurately predict the natural history, it is important that all patients undergo longitudinal follow-up at least twice a year for the first few years following diagnosis. The treatment of PLCH is challenging and should be individualised. While there is no general consensus regarding the role of immunosuppression or chemotherapy in management, selected patients may experience improvement in lung function with therapy. Determination of BRAFV600E or other mutations may assist with the development of an individualised approach to therapy. Patients with progressive disease should be referred to specialised centres and considered for a trial of pharmacotherapy or evaluated for transplantation.

Idiopathic thrombocytopenic purpura in childhood, Langerhans cell histiocytosis in adulthood: More than a chance association?

Described herein, a case of Langerhans cell histiocytosis (LCH) in an adult with Idiopathic Thrombocytopenic Purpura (ITP) diagnosed at age ten. She presented with cranial diabetes insipidus, later developed hypogonadotrophic hypogonadism and multiple cervical lympadenopathy from which histopathology of excisional biopsy confirmed LCH. Magnetic resonance imaging showed thickened pituitary stalk. Association of ITP and LCH is unknown but the question of LCH presenting as isolated thrombocytopenia in childhood only to be discovered in adulthood when there was pituitary and bone involvement remains. It reemphasizes the need for high index of suspicion and the challenges in diagnosing LCH at the outset.

Mutually exclusive extracellular signal-regulated kinase pathway mutations are present in different stages of multi-focal pulmonary Langerhans cell histiocytosis supporting clonal nature of the disease.

AIMS: Pulmonary Langerhans cell histiocytosis (PLCH) is an idiopathic cigarette smoking-related disorder of the lung. Molecular changes in cellular or fibrotic stages of PLCH have not been investigated. We studied the prevalence of extracellular signal-regulated kinase (ERK) pathway mutations in different PLCH stages and other non-PLCH smoking-related lung diseases. METHODS AND RESULTS: The cohort included 28 PLCH with cellular (n = 10), mixed cellular/fibrotic (n = 4) and fibrotic histology (n = 14). Seven cases had concurrent multi-focal/multi-lobar tumours. Respiratory bronchiolitis interstitial lung disease (RB-ILD, n = 2), desquamative interstitial pneumonia (DIP, n = 4) and mixed RB-ILD/DIP (n = 2) were included for comparison. BRAF(V) (600E) immunohistochemistry, next-generation sequencing (NGS) and peptide nucleic acid (PNA) clamp polymerase chain reaction (PCR) with high analytical sensitivity (<0.1-0.2%) were used to analyse RAS, BRAF and MAP2K1 genes. Of 26 cases with gene mutation data, BRAF(V) (600E) was identified in eight of 12 (67%) cellular cases and in one of 14 (7%) fibrotic cases. MAP2K1 or KRAS mutations were observed in four of 14 (29%) fibrotic cases and three of the 12 (25%) cellular cases. Multi-focal/multi-lobar specimens carried identical BRAF (n = 5) or non-hotspot MAP2K1 (n = 2) mutations. The other smoking-related disorders were negative for mutations. Patients with cellular lesions or BRAF mutation were significantly younger than patients with fibrotic or BRAF wild-type PLCH. CONCLUSION: The presence of identical but mutually exclusive ERK pathway mutations in multi-focal PLCH supports a neoplastic/clonal origin for this disease. Patient age and mutation type differed between cellular and fibrotic histology and may indicate a natural progression or a mutation-specific pathogenicity.

Smoking-related idiopathic interstitial pneumonia: A review.

For many years, cigarette smoking has been considered as the leading cause of chronic obstructive pulmonary disease and lung cancer. Recently, however, it has also been associated with the development of diffuse interstitial lung diseases. In the latest classification of the major idiopathic interstitial pneumonias (IIP), the term smoking-related IIP has been introduced, including two entities, namely desquamative interstitial pneumonia (DIP) and respiratory bronchiolitis-interstitial lung disease (RB-ILD). Other entities in which smoking has a definite or suggested role include pulmonary Langerhan's cell histiocytosis, smoking-related interstitial fibrosis, combined pulmonary fibrosis and emphysema syndrome and idiopathic pulmonary fibrosis. In this review, we will focus on the mechanisms of smoking-related lung damage and on the clinical aspects of these disorders with the exception of idiopathic pulmonary fibrosis, which will be reviewed elsewhere in this review series.

Chromium-induced diffuse dermatitis with lymph node involvement resulting from Langerhans cell histiocytosis after metal-on-metal hip resurfacing.

Total hip arthroplasty (THA) is a highly effective surgical treatment for severe joint involvement. However, due to the release of metal ions in the blood, the patients who undergo hip replacement with metal-on-metal (MOM) bearings may develop signs of allergic skin disease. We report a case of a 60-year-old man who had received MOM hip resurfacing 5 years earlier for osteoarthritis. He presented with a 3-year history of diffuse dermatitis that did not respond to antihistamines and corticosteroids and also had elevated serum levels of chromium and cobalt. A patch test revealed chromium-sulfate hypersensitivity. A skin biopsy showed nonspecific perivascular lymphocytic infiltrate associated with histiocytes. A biopsy of an inguinal lymph node demonstrated large aggregates of Langerhans cells, suggesting type IV delayed-type hypersensitivity. The prosthesis was replaced using ceramic-on-ceramic bearings and the dermatitis resolved after 3 months. The lymph nodes decreased in volume and the serum chromium levels normalized within 24 months of revision surgery. The high levels of serum ions associated with the metal debris from MOM-THAs may induce sensitization and type IV hypersensitivity reactions. Replacing the prosthesis using alternative coupling surfaces is the only approach that has the capacity to resolve these symptoms. Physicians who are not familiar with this issue may misdiagnose systemic symptoms and provide inadequate treatment.

New insights into the molecular pathogenesis of langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare proliferative disorder characterized by an accumulation of cells sharing the major phenotypic features of cutaneous Langerhans cells. Given its variable clinical evolution, ranging from self-limiting lesions to multisystemic forms with a poor prognosis, in the last decades it has been debated whether LCH might not have a neoplastic rather than an inflammatory nature. However, although the fundamental events underlying the pathogenesis of LCH are still elusive, recent advances have strikingly improved our understanding of the disease. In particular, the identification of multiple interplays between LCH cells and their tumor microenvironment, along with the recognition of the lesional cytokine storm as a key determinant of LCH progression, has substantiated new opportunities for devising targeted therapeutic approaches. Strikingly, the detection of the rapidly accelerated fibrosarcoma isoform B(V600E) gain-of-function mutation as a genetic alteration recurring in more than 50% of patients has fueled the paradoxical picture of LCH as a tumor of the antigen-presenting cells that can evade rejection by the immune system. Thus, new evidence regarding the ontogeny of LCH cells, as well as a better understanding of the putative immune system frustrating strategy in LCH, may help to define the precise pathogenesis.

Pulmonary Langerhans cell histiocytosis and diabetes insipidus in pregnant women: our experience.

Pulmonary Langerhans cell histiocytosis (PLCH) occurs predominantly in young adult smokers. Diabetes insipidus occurs in up to 15 % patients with PLCH. Information on PLCH in pregnancy is sparse, especially associated with diabetes insipidus. We report three patients with these conditions and describe the disease history and pregnancy outcomes.

Lupus Vulgaris Erythematoides: report of a patient initially misdiagnosed as dermatitis.

A small percentage of patients with tuberculosis present with cutaneous findings, which may be difficult to diagnose. We present a patient diagnosed with a rare, non-scarring form of cutaneous tuberculosis (CTB), classically termed as lupus vulgaris erythematoides.

Langerhans cell histiocytosis and Erdheim-Chester disease.

PURPOSE OF REVIEW: To provide an updated overview of the pathogenesis and treatment of Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD). RECENT FINDINGS: There is ongoing debate as to the exact pathogenesis of these disorders and their classification as reactive versus neoplastic. Proinflammatory cytokines are known to play a role in both LCH and ECD and strengthen the hypothesis that, at least in part, they are disorders of immune dysregulation. The recent discovery of activating mutations in the proto-oncogene BRAF in a subset of LCH patients suggests that LCH is in fact a neoplastic disorder. Understanding of the mechanisms that promote proliferation and migration of histiocytes has led researchers to explore targeted immune-modulatory therapies for ECD. Similarly for LCH, alternative chemotherapeutic agents and reduced-intensity hematopoietic stem cell transplant are being evaluated for refractory disease. SUMMARY: More research is needed to better understand the cause of these disorders and may help in identifying new targeted therapies, particularly for patients with refractory or relapsed disease. Multinational trials are ongoing for LCH and are urgently needed for ECD.

Langerhans cell histiocytosis with central nervous system involvement--complete response to 2-chlorodeoxyadenosine after failure of tyrosine kinase inhibitor therapies with sorafenib and imatinib.

Langerhans cell histiocytosis (LCH) is rare in adults, and only a subset of these patients suffers from central nervous system (CNS) involvement. Hence, evidence-based treatment recommendations are lacking. A case of a 20-year-old student with multisystem LCH and extensive CNS involvement is described, who showed a durable response to 2-chlorodeoxyadenosine after prior therapies with the tyrosine kinase inhibitors sorafenib and imatinib. In accordance to the experiences provided by other case series, which are reviewed herein, 2-chlorodeoxyadenosine can be considered an effective and safe option for adult LCH with CNS involvement.

Langerhans cell histiocytosis in children born 1982-2005 after in vitro fertilization.

AIM: In a recent Swedish study, comparing data from the Swedish Cancer Register with the Medical Birth Register including data on IVF, an increased risk of Langerhans cell histiocytosis (LCH) was found in children born 1982-2005 after IVF. Here, we aimed to verify the LCH diagnoses and examine whether any special forms of the disease were overrepresented in this population. METHODS: Medical records for all children with LCH conceived by IVF were acquired and the diagnosis confirmed or discarded. Disease characteristics were compared with data from children diagnosed with LCH 1992-2001 in the Stockholm County. RESULTS: We verified LCH in seven children born after IVF, all born prior to 2002. These children did not have milder disease forms. The odds ratio (OR) to develop LCH for the whole group born after IVF was 3.2 [95% confidence interval (CI), 1.4-7.3] and for children born before 2002, 5.2 [95% CI, 2.3-11.9], compared with children in Stockholm County 1992-2001. CONCLUSION: LCH was overrepresented in children born after IVF prior to 2002. Affected children did not have milder disease forms. These findings may be valuable to understand LCH aetiology. Additional studies on a putative correlation between IVF and LCH in the offspring are encouraged.