Langerhans cell histiocytosis: fascinating dynamics of the dendritic cell-macrophage lineage

Polyclonal T-cells express CD1a in Langerhans cell histiocytosis (LCH) lesions

Langerhans cell histiocytosis (LCH) is a complex and poorly understood disorder that has characteristics of both inflammatory and neoplastic disease. By using eight-colour flow cytometry, we have identified a previously unreported population of CD1a(+)/CD3(+) T-cells in LCH lesions. The expression of CD1a is regarded as a hallmark of this disease; however, it has always been presumed that it was only expressed by pathogenic Langerhans cells (LCs). We have now detected CD1a expression by a range of T-cell subsets within all of the LCH lesions that were examined, establishing that CD1a expression in these lesions is no longer restricted to pathogenic LCs. The presence of CD1a(+) T-cells in all of the LCH lesions that we have studied to date warrants further investigation into their biological function to determine whether these cells are important in the pathogenesis of LCH.

Granulomatous inflammation: The overlap of immune deficiency and inflammation

Pediatric granulomatous diseases constitute a heterogenous group of conditions in terms of clinical phenotypes, pathogenic mechanisms, and outcomes. The common link is the presence of multinucleated giant cells in the inflammatory infiltrate. The clinical scenario in which a tissue biopsy shows granulomatous inflammation is not an uncommon one for practicing adult and pediatric rheumatologists. Our role as rheumatologists is to develop a diagnostic plan based on a rational differential diagnostic exercise tailored to the individual patient and based mainly on a detailed clinical assessment. This chapter presents a comprehensive differential diagnosis associated with a classification developed by the authors. We describe with some detail extrapulmonary sarcoidosis, Blau syndrome, and immunodeficiency associated granulomatous inflammation, which in our view are the paradigmatic primary forms of granulomatous diseases in childhood. The other entities are presented only as differential diagnoses listing their most relevant clinical features. This chapter shows that almost all granulomatous diseases seen in adults can be found in children and that there are some entities that are essentially pediatric at onset, namely Blau syndrome and most forms of immunodeficiency associated granulomatous diseases.

Somatic activating ARAF mutations in Langerhans cell histiocytosis

The extracellular signal-regulated kinase (ERK) signaling pathway is activated in Langerhans cell histiocytosis (LCH) histiocytes, but only 60% of cases carry somatic activating mutations of BRAF. To identify other genetic causes of ERK pathway activation, we performed whole exome sequencing on purified LCH cells in 3 cases. One patient with wild-type BRAF alleles in his histiocytes had compound mutations in the kinase domain of ARAF. Unlike wild-type ARAF, this mutant was a highly active mitogen-activated protein kinase kinase in vitro and was capable of transforming mouse embryo fibroblasts. Mutant ARAF activity was inhibited by vemurafenib, a BRAF inhibitor, indicating the importance of fully evaluating ERK pathway abnormalities in selecting LCH patients for targeted inhibitor therapy.

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.

Dendritic cell-based approaches for therapeutic immune regulation in solid-organ transplantation

To avoid immune rejection, allograft recipients require drug-based immunosuppression, which has significant toxicity. An emerging approach is adoptive transfer of immunoregulatory cells. While mature dendritic cells (DCs) present donor antigen to the immune system, triggering rejection, regulatory DCs interact with regulatory T cells to promote immune tolerance. Intravenous injection of immature DCs of either donor or host origin at the time of transplantation have prolonged allograft survival in solid-organ transplant models. DCs can be treated with pharmacological agents before injection, which may attenuate their maturation in vivo. Recent data suggest that injected immunosuppressive DCs may inhibit allograft rejection, not by themselves, but through conventional DCs of the host. Genetically engineered DCs have also been tested. Two clinical trials in type-1 diabetes and rheumatoid arthritis have been carried out, and other trials, including one trial in kidney transplantation, are in progress or are imminent.

Cancer risk in children and adolescents with birth defects: a population-based cohort study

Objective

Birth defects are an increasing health priority worldwide, and the subject of a major 2010 World Health Assembly Resolution. Excess cancer risk may be an added burden in this vulnerable group of children, but studies to date have provided inconsistent findings. This study assessed the risk for cancer in children and young adolescents with major birth defects.

Methods and Findings

This retrospective, statewide, population-based, cohort study was conducted in three US states (Utah, Arizona, Iowa). A cohort of 44,151 children and young adolescents (0 through 14 years of age) with selected major, non-chromosomal birth defects or chromosomal anomalies was compared to a reference cohort of 147,940 children without birth defects randomly sampled from each state’s births and frequency matched by year of birth. The primary outcome was rate of cancer prior to age 15 years, by type of cancer and type of birth defect. The incidence of cancer was increased 2.9-fold (95% CI, 2.3 to 3.7) in children with birth defects (123 cases of cancer) compared to the reference cohort; the incidence rates were 33.8 and 11.7 per 100,000 person-years, respectively. However, the excess risk varied markedly by type of birth defect. Increased risks were seen in children with microcephaly, cleft palate, and selected eye, cardiac, and renal defects. Cancer risk was not increased with many common birth defects, including hypospadias, cleft lip with or without cleft palate, or hydrocephalus.

Conclusion

Children with some structural, non-chromosomal birth defects, but not others, have a moderately increased risk for childhood cancer. Information on such selective risk can promote more effective clinical evaluation, counseling, and research.

Multisystem Langerhans cell histiocytosis presenting as an oral lesion

Langerhans cell histiocytosis (LCH) is a rare proliferative disorder in which the pathologic Langerhans cells infiltrate and destroy the tissues. Patients with LCH present varied clinical manifestations. Cutaneous lesions in LCH manifest as vesiculopapular eruptions that often mimic various infectious diseases particularly in infants. We present a case of a female infant with an ulcerative lesion intraorally. The baby was asymptomatic otherwise. A detailed history revealed the presence of cutaneous lesions that was overlooked by her parents.

CONCLUSION

This report tries to briefly discuss the current concepts regarding the etiology of LCH. An attempt has been made to emphasis the need for a through systemic examination. The protocol of investigative procedures to be adopted in LCH is also discussed.

Hypothetical pathogenesis of eosinophilic infiltration in Langerhans cell histiocytosis of the jaw

OBJECTIVE

The present study investigated the densities of mast cells and CCL-11/eotaxin-1 expression of tumor cells in Langerhans cell histiocytosis (LCH) of the jaw.

STUDY DESIGN

Eleven LCH cases arising in the jaws were selected. We evaluated eotaxin-1 expression in LCH cells via immunohistochemical staining. Toluidine blue was used to stain mast cells, with 20 periapical granuloma specimens serving as the control group.

RESULTS

In all 7 patients with multifocal LCH, jaw lesions were the earliest manifestation. Toluidine blue staining revealed that most of the mast cells involved in LCH were degranulated, and the number of mast cells in LCH lesions was not significantly higher than in periapical granulomas. Upon immunohistochemical examination, all patients but one showed positivity for eotaxin-1 in LCH cells.

CONCLUSION

This preliminary study suggests that eotaxin-1 expression in LCH cells may contribute to eosinophilic infiltration. Further studies of chemokine-receptor interactions will be needed to confirm this.

Targeting BCL2 family in human myeloid dendritic cells: a challenge to cure diseases with chronic inflammations associated with bone loss

Rheumatoid arthritis (RA) and Langerhans cell histiocytosis (LCH) are common and rare diseases, respectively. They associate myeloid cell recruitment and survival in inflammatory conditions with tissue destruction and bone resorption. Manipulating dendritic cell (DC), and, especially, regulating their half-life and fusion, is a challenge. Indeed, these myeloid cells display pathogenic roles in both diseases and may be an important source of precursors for differentiation of osteoclasts, the bone-resorbing multinucleated giant cells. We have recently documented that the proinflammatory cytokine IL-17A regulates long-term survival of DC by inducing BCL2A1 expression, in addition to the constitutive MCL1 expression. We summarize bibliography of the BCL2 family members and their therapeutic targeting, with a special emphasis on MCL1 and BCL2A1, discussing their potential impact on RA and LCH. Our recent knowledge in the survival pathway, which is activated to perform DC fusion in the presence of IL-17A, suggests that targeting MCL1 and BCL2A1 in infiltrating DC may affect the clinical outcomes in RA and LCH. The development of new therapies, interfering with MCL1 and BCL2A1 expression, to target long-term surviving inflammatory DC should be translated into preclinical studies with the aim to increase the well-being of patients with RA and LCH.

Resorption of PDLLA plates as a nidus for recurrent langerhans cell histiocytosis

Resorbable plating systems have been adapted into routine use for craniofacial reconstruction in children. After implantation in some patients, the area around the plates can develop palpable and visible fibrous capsules, with underlying bone resorption and a significant foreign-body giant cell reaction. The reaction is usually self-limited. We report a case in which Langerhans cell histiocytosis was resected, and then recurred at the sites of resorbing plate and screw placement in association with a foreign-body giant cell reaction.

Langerhans cell sarcoma with an aberrant cytoplasmic CD3 expression

Abstract

Langerhans cell sarcoma is a rare and aggressive high grade hematopoietic neoplasm with a dismal prognosis. It has a unique morphological and immunotypic profile with a CD1a/ langerin/S100 + phenotype. T cell lineage markers except for CD4 in Langerhans cell sarcoma have not been documented previously. We report a case of 86 year-old male of Caucasian descent who presented with an enlarging right neck mass over 2 months with an underlying unknown cause of anemia. Computed tomography scan of the neck, chest and abdomen revealed generalized lymphadenopathy and mild splenomegaly suspicious for lymphoma. Diagnostic core biopsy performed on right neck mass revealed a possible T cell lymphoma with expression of T cell lineage specific marker CD3 but conclusive diagnosis could not be made due to insufficient core biopsy sample. Further excisional biopsy performed on a left inguinal node showed a hematopoietic neoplasm with features of Langerhans cell sarcoma with a focal cytoplasmic CD3 expression in 30-40% of the tumor cells. PCR for T cell receptor (TCR) gene rearrangement failed to demonstrate a clonal gene rearrangement in the tumor cells arguing against a T cell lineage transdifferentiation, suggesting an aberrant CD3 expression. To the best of our knowledge, this case represents the first report of Langerhans cell sarcoma with an aberrant cytoplasmic CD3 expression.

Virtual slides

http://www.diagnosticpathology.diagnomx.eu/vs/2065486371761991

[Monosystemic, oligolesional Langerhans cell histiocytosis. A rare congenital dermatosis]

A five-day-old female infant presented with congenital red-livid papules and nodules on the head, chest, back and left arm. The nodule on the chest was ulcerated at birth. The pregnancy and delivery were uneventful. There was no history of birth trauma to account for the ulcerated lesion. The parents and the three older siblings were healthy without similar skin lesions. The skin biopsy showed in the deep layer of the dermis a multinodular, granulomatous histiocytic infiltrate. The histiocytic cells expressed S-100 and CD1a. There were additionally many eosinophils. The suspected diagnosis Langerhans cell histiocytosis was confirmed by the histologic results. The patient was referred to pediatric hematology-oncology where evaluation showed no evidence of systemic involvement. The clinical, radiological, sonographic and histological results led to the diagnosis of a congenital, monosystemic, oligolesional Langerhans cell histiocytosis of the skin. In addition to the case presentation, we review the current stand of knowledge of the pathogenesis, the clinical classification and the therapy of the Langerhans cell histiocytosis.

Langerhans's cell histiocytosis in old subjects: two rare case reports and review of the literature

BACKGROUND

Langerhans cell histiocytosis (LCH) is a proliferative disease of histiocyte-like cells that generally affects children; LCH onset is rare in adults; immunohistochemistry is essential to obtain the correct diagnosis, and treatment protocols are controversial.

OBJECTIVE

To describe two new cases of adult onset oral LCH.

CASE REPORTS

Case 1: a 71-year-old woman, complaining of diffuse oral pain, presented with erythematous mucosal lesions; the panoramic radiograph and CT scan showed multiple mandible radiolucent areas. Immunohistochemical assay for S-100, CD1a and langerin test was essential in reaching the correct diagnosis. Case 2: a 77-year-old female patient presented with a non-painful, non-bleeding, slightly elevated erythematous palatal lesion of 6 months duration, together with a genital vulvar lesion of uncertain nature. The pathology confirmed the diagnosis of LCH. Many therapies (etoposid, radiotherapy) could induce only a clinical partial remission; Cladribine induced a complete recovery.

CONCLUSION

The first case was difficult to diagnose: the clinical presentation and course of the disease (LCH) in the elderly are multiple and unpredictable. An immunohistochemistry study is often essential to obtain the correct diagnosis. The second case required several therapeutic interventions: even though some cases regress spontaneously, others require systemic chemotherapy.

B-RAF mutant alleles associated with Langerhans cell histiocytosis, a granulomatous pediatric disease

BACKGROUND

Langerhans cell histiocytosis (LCH) features inflammatory granuloma characterised by the presence of CD1a+ dendritic cells or 'LCH cells'. Badalian-Very et al. recently reported the presence of a canonical (V600E)B-RAF mutation in 57% of paraffin-embedded biopsies from LCH granuloma. Here we confirm their findings and report the identification of two novel B-RAF mutations detected in LCH patients.

METHODS AND RESULTS

Mutations of B-RAF were observed in granuloma samples from 11 out of 16 patients using 'next generation' pyrosequencing. In 9 cases the mutation identified was (V600E)B-RAF. In 2 cases novel polymorphisms were identified. A somatic (600DLAT)B-RAF insertion mimicked the structural and functional consequences of the (V600E)B-RAF mutant. It destabilized the inactive conformation of the B-RAF kinase and resulted in increased ERK activation in 293 T cells. The (600DLAT)B-RAF and (V600E)B-RAF mutations were found enriched in DNA and mRNA from the CD1a+ fraction of granuloma. They were absent from the blood and monocytes of 58 LCH patients, with a lower threshold of sequencing sensitivity of 1%-2% relative mutation abundance. A novel germ line (T599A)B-RAF mutant allele was detected in one patient, at a relative mutation abundance close to 50% in the LCH granuloma, blood monocytes and lymphocytes. However, (T599A)B-RAF did not destabilize the inactive conformation of the B-RAF kinase, and did not induce increased ERK phosphorylation or C-RAF transactivation.

CONCLUSIONS

Our data confirmed presence of the (V600E)B-RAF mutation in LCH granuloma of some patients, and identify two novel B-RAF mutations. They indicate that (V600E)B-RAF and (600DLAT)B-RAF mutations are somatic mutants enriched in LCH CD1a(+) cells and absent from the patient blood. Further studies are needed to assess the functional consequences of the germ-line (T599A)B-RAF allele.

Langerhans cell histiocytosis - a case report

A 17-year-old male presented for dermatologic consultation with slightly elevated reddish papules covered by yellowish scales in the scalp for the last two years and reddish and indurated ulcers in the perineum lasting six months. Additional complaints included polyuria, polydipsia, delay in the development of secondary sexual characteristics and hearing loss of the right ear secondary to a medium otitis. Lesions from scalp and perineum were sampled for histopathologic examination and revealed a dense cellular infiltrate made up of mononuclear cells with conspicuous eosinophilic cytoplasm and large cleaved vesicular nucleus, some of them with shapes resembling the format of a kidney and others reminiscent of coffee beans. Numerous intermingling eosinophils were present. The diagnosis of Langerhans cell histiocytosis was then rendered and confirmed by positive immunostaining of neo-plastic cells for anti-CD1a and anti-S100 protein antibodies. The work-up revealed diabetes insipidus, hypogonadotropic hypogonadism, hiperprolactenemia, growing-hormone deficiency and thickness of the pituitary stalk. The patient was treated with prednisone and vinblastin based chemotherapy regimen for six months with complete remission, but presented recurrence of some lesions in the scalp, which were handled with topical mustard and corticosteroids. After chemotherapy, the endocrinologic disturbances were corrected with hormonal replacement therapy. The patient is currently in good health with a follow-up of five years.

Spontaneous regression of pulmonary involvement after smoking reduction and removal of and radiation therapy for Langerhans cell histiocytosis of the sphenoid bone: which comes first, the chicken or the egg?

Isolated pulmonary Langerhans cell histiocytosis (LCH) in adults is known to regress spontaneously after smoking cessation alone, but little is known about whether this rationale could also apply in cases of multisystem pulmonary LCH. In particular, pediatric patients with multisystem LCH including involvement in "risk organs" such as lungs often benefit from systemic chemotherapy. Here, we present a 37-year-old man with spontaneous regression of pulmonary lesions in multisystem LCH, achieved solely by smoking reduction following local treatment of bone lesions.

Langerhans cell histiocytosis preceding the development of juvenile xanthogranuloma: a case and review of recent developments

Langerhans cell histiocytosis (LCH) and juvenile xanthogranuloma (JXG) both belong to the histiocytosis group of disorders, which have varied prognostic and clinical significance. Their normal cellular counterparts share a common CD34-positive hematopoietic stem cell precursor that matures along CD14-negative or -positive pathways. Rare cases of LCH and JXG show overlapping findings, suggesting that this divergent maturation is not irreversible. We report a case of an infant diagnosed with cutaneous LCH shortly after birth. Two years after diagnosis, a recurrent lesion in his external auditory canal contained lipidized cells with CD68 and factor XIIIa expression and lacked Birbeck granules and CD1a, consistent with JXG. Our case and previous reports of this phenomenon raise the question of a histogenic relationship between LCH and JXG, and we speculate that the lesional cells of origin are subjected to therapy-induced modulation that results in a varied differentiation.

Neither IL-17A mRNA nor IL-17A protein are detectable in Langerhans cell histiocytosis lesions

Langerhans cell histiocytosis (LCH) is a rare disease characterized by heterogeneous lesions including CD207(+)/CD1a(+) dendritic cells that can result in significant morbidity and mortality. The etiology of LCH remains speculative, and neoplastic and inflammatory origins have been debated for decades. A recent study identified abundant interleukin-17 (IL-17A) protein in dendritic cells in LCH lesions as well as in plasma from patients with active disease. Furthermore, it identified dendritic cells as a novel source of IL-17A expression. However, subsequent studies from our research group failed to identify any IL-17A gene expression from CD207(+) dendritic cells or CD3(+) T cells in LCH lesions. In this study, further investigation once again fails to identify any cells in LCH lesions with IL-17A gene expression. Furthermore, IL-17A antigen is undetectable in LCH lesion lysates with western blotting, immunoprecipitation, spectral analysis, and enzyme-linked immunosorbent assay (ELISA). Western blots, immunoprecipitation, and ELISA experiments also demonstrate that antibodies used in original studies that established the IL-17A hypothesis for pathogenesis of LCH recognize nonspecific proteins. We conclude that evidence for IL-17A as a significant factor in LCH remains inadequate and clinical trials targeting IL-17A remain unjustified.

Multisystem Langerhans cell histiocytosis in children: current treatment and future directions

Langerhans cell histiocytosis (LCH) is a rare (about 3-5 cases per million children aged 0-14 years), non-malignant disease characterized by proliferation and accumulation of clonal dendritic cells, extreme clinical heterogeneity, and an unpredictable course. Three large-scale, international, prospective therapeutic studies (LCH-I to III) for multisystem LCH (MS-LCH) have been conducted by the Histiocyte Society since 1991. The cumulative lessons from these studies are summarized in this review. Patients with MS-LCH represent a heterogeneous group with respect to disease severity and outcome, therefore treatment stratification and risk-tailored treatment are mandatory. The risk for mortality can be predicted based on involvement of 'risk organs' (e.g. hematopoietic system, liver, and/or spleen) at diagnosis and on response to initial therapy (assessed after 6-12 weeks of treatment). Thus, patients without involvement of risk organs (low-risk group) are not at risk for mortality but need systemic therapy in order to control the disease activity and avoid reactivations and permanent consequences. Patients with risk organ involvement (risk group) are at risk for mortality, and lack of therapy response defines a subgroup with a particularly dismal prognosis (high-risk group). Those patients in the risk group who respond to therapy and survive are at risk for reactivations and permanent consequences. The LCH-I study compared the efficacy of vinblastine and etoposide, and concluded that they are equivalent single-agent treatments for children with MS-LCH. However, the results of this trial were inferior with respect to response rate at week 6, disease reactivation rate, and sequelae, when compared with historical trials using more intensive regimens. The combination of prednisolone and vinblastine was established as a standard first-line treatment through the LCH-II and LCH-III studies. The regimen consists of one to two 6-week courses (continuous oral corticosteroids 40 mg/m2/day for 4 weeks, tapered over 2 weeks plus weekly vinblastine intravenous push) of initial therapy, followed by a continuation phase (three weekly pulses of oral prednisolone 40 mg/m2/day for 5 days plus a vinblastine injection). The addition of a third drug to the standard combination (etoposide in LCH-II and methotrexate in LCH-III) failed to significantly improve survival in the risk group. The remaining mortality in the risk group is about 20%, and up to 40% in the high-risk group. Concerning low-risk MS-LCH, comparison of results of the LCH-II study with historical data suggested that the remaining reactivation rate of about 50% (and possibly permanent consequences) could be reduced by prolongation of the total treatment duration. To study this hypothesis, in the low-risk group of the LCH-III study standard maintenance therapy was randomly given for a total treatment duration of 6 and 12 months. Unpublished preliminary data from this recently closed trial suggested that prolongation of the treatment duration may significantly improve reactivation-free survival. In summary, several studies have shown that systemic therapy is indicated for all patients with MS-LCH. A standard two-drug regimen consisting of an initial 'intensive' phase for 6-12 weeks, followed by a less intensive 'maintenance phase' for a total treatment duration of at least 12 months is recommended for patients treated outside of clinical trials. Non-responders, particularly those with progressive disease in risk organs, are eligible for experimental salvage approaches. Remaining questions will be addressed in the upcoming LCH-IV trial, which is in the process of intensive preparation.