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Granulomatous Diseases
Published in Ayşe Serap Karadağ, Lawrence Charles Parish, Jordan V. Wang, Roxburgh's Common Skin Diseases, 2022
Albert Alhatem, Robert A. Schwartz, Muriel W. Lambert, W. Clark Lambert
Overview: Xanthogranuloma (XG) is a moderately uncommon, benign, proliferative histiocytic disorder, which originates from dermal factor XIIIa positive dendrocytes. It is the most common of the non-Langerhans cell histiocytosis, occurring predominantly in young children.
Progressive mucinous histiocytosis treated successfully with thalidomide: a rare case report
Published in Journal of Dermatological Treatment, 2023
Reem Diab, Mohammad Shahidi Dadras, Azadeh Rakhshan, Ali Kaddah, Fahimeh Abdollahimajd
Histiocytosis is divided into two sub-groups: Langerhans and non-Langerhans cell histiocytosis, distinguished by the immunophenotype of the affected cells (3). Langerhans cell histiocytosis (LCH) includes Letterer–Siwe disease, Hand-Schüller-Christian disease, eosinophilic granuloma, congenital self-healing, and adult LCH, staining positively for CD1a, S100 protein, and CD207 (langerin), and negatively for CD68, CD163, and factor XIIIa (3). Non-Langerhans cell histiocytosis (non-LCH) is divided into three subgroups: primarily cutaneous, cutaneous with systematic involvement, and primarily extra-cutaneous in addition to skin involvement (4). Non-LCH includes juvenile xanthogranuloma, xanthoma disseminatum, benign cephalic histiocytosis, progressive nodular histiocytosis, spindle cell xanthogranuloma, and generalized eruptive histiocytosis, which are of dendritic origin; HPMH was later added to this group (5).
Short-term response to alemtuzumab in CD52-positive secondary histiocytic sarcoma in a child: Is it time to consider new targets?
Published in Pediatric Hematology and Oncology, 2020
Elvis Terci Valera, María Sol Brassesco, Maristella Bergamo Francisco dos Reis, Gilberto Maggioni, Renato Luiz Guerino-Cunha, Carlos Eduardo Grecco, Jorge Elias Jr., Mery Kato, Luiz Gonzaga Tone
Histiocytic and macrophage-dendritic neoplasms are very uncommon tumors with variable clinical behavior. Current classification proposal stratifies these lesions into five main groups: L (Langerhans), C (Cutaneous and mucocutaneous histiocytosis), R (Rosai-Dorfman Disease and miscellaneous noncutaneous, non-Langerhans cell histiocytosis), M (Malignant histiocytosis) and H (Hemophagocytic lymphohistiocytosis and macrophage activation syndrome).2 A large spectrum of histiocytic lesions has been described in association with leukemia in children.3 These lesions range from benign, locally aggressive, to highly malignant tumors. HS is a subtype of malignant histiocytosis considered a very aggressive and potentially lethal end of this spectrum where genetic information and new insights supporting precision therapies are warranted. Owing to the paucity of clinical and genetic information on pediatric cases of secondary HS following ALL, our brief report aimed to add a thorough description on both clinical and genetic findings of this association in a child. Clinical experience with targeted-therapy as a rescue regimen using alemtuzumab is also described. In addition, we proposed to gather and to explore the most frequent mutations and leading cell pathways involved in this SMN described in pediatric cases to date.
Erdheim–Chester disease and vemurafenib: a review of ophthalmic presentations and clinical outcomes
Published in Orbit, 2023
Ji Kwan Park, Laura C. Huang, Andrea L. Kossler
Previously classified as a non-Langerhans cell histiocytosis, ECD is now increasingly understood as a disorder with similar pathogenetic mechanisms to Langerhans cell histiocytosis (LCH).21,22 Initially, the identification of high levels of pro-inflammatory chemokines including TNF-α, interferon-α, interleukin-1, interleukin-6, interleukin-12, and monocyte chemotactic protein-1 (MCP1/CCL2) suggested a type 1 T-helper cell differentiation and activation necessary for systemic signaling.23 Infliximab, anakinra, and tocilizumab have been used to inhibit these inflammatory cytokines.24 Recent genetic and molecular advances have contributed to understanding the pathophysiology of ECD as an alteration in the mitogen-activated protein kinase (MAPK) pathway and PIK3CA-AKT-mTOR pathway that produces dysregulated cell survival with failure of apoptosis and subsequent proliferation of histiocytes (Figure 1).24–26 Specific mutations in the RAS-RAF-MEK-ERK-MAPK (RAS-RAF-MAPK) pathway result in an uncontrolled stimulation of receptor tyrosine kinases that may act as a proto-oncogene “gain of function” mutation.27–29 Activating mutations in BRAF-V600E exist in 54% of ECD patients, which can be detected in biopsies.30 This amino acid substitution from valine to glutamic acid results in uncontrolled cell growth.31 Target inhibition of the mutated BRAF-V600E is the primary mechanism of action in vemurafenib and dabrafenib.24 Cobimetinib and trametinib are MEK inhibitors that target the MAPK pathway when BRAF-V600E mutation is absent. In a review of 38 cases investigated for genetic mutations for ECD, somatic mutations involving BRAF (66%), MAP2K1 (16%, but as high as 30%), ARAF (5%), MAP2K2 (3%), KRAS and NRAS (3%, but as high as 27%), PIK3CA (11%), MAP2K1 and a PIK3CA mutation (3%) were detected.24,32 Moreover, the phosphorylated forms of mTOR are expressed by the foamy histiocytes in ECD.33 Sirolimus and everolimus are mTOR inhibitors that interfere with the PI3K-AKT pathway.24 Additionally, it has been shown that both LCH and ECD demonstrate clonal mutations involving genes of the MAPK pathway in greater than 80% of cases.30 Due to this new understanding of the pathogenesis underlying these disorders, a recently proposed classification has been introduced that classifies ECD and LCH within the same category of histiocytic disease, reflecting the currently modified categorization of histiocytic disorders.28