Aberrant expression of CD10 in ground-glass-like multinucleated giant cells of multicentric reticulohistiocytosis

Reticulohistiocytoses: a revision of the full spectrum

Reticulohistiocytoses (RH) are rare and clinically heterogeneous histiocytic disorders of dermatological interest. Three clinical entities with superimposable histopathological features are currently considered, namely solitary reticulohistiocytoma, diffuse/generalized reticulohistiocytosis and multicentric reticulohistiocytosis. Although in the last decade, RH studies have only minimally progressed, histiocytosis research has advanced considerably: the prognostic and therapeutic importance of the clinical subclassification of histiocytosis patients as well as of the detection of genetic alterations in the genes of the ERK pathway has been highlighted. According to these insights, we previously reported the presence of molecular alteration RH and described a subset of patients with disseminated multisystem involvement lacking arthritis. In the present review, we aim to update and revise the knowledge regarding RH. We first reviewed their histopathological, immunophenotypical and ultrastructural features, discussed their histopathological differential diagnosis with other conditions characterized by infiltrates made of oncocytic or epithelioid cells (with special regard to Destombes-Rosai-Dorfman disease) and finally summarized the molecular landscape of RH. We therefore tried to adjust the clinical subclassification of Langerhans cell histiocytosis to the clinical phenotypes of RH, outlining five clinically different groups of patients. Finally, we reconsidered the clinical workflow to the evaluation of RH patients, in light of the 5 different clinical groups and discussed the different therapeutic approaches and the possible role of target inhibitors.

Tumor necrosis factor antagonists in the treatment of multicentric reticulohistiocytosis: Current clinical evidence

Multicentric reticulohistiocytosis (MRH) is a rare and debilitating systemic disorder characterized by cutaneous nodules and destructive polyarthritis. Due to its unknown etiology, the treatment of MRH varies with different rates of success, which causes treatment options to be rather independent and empirical. In the present study, a case of a 48‑year‑old woman with a 12‑month history of polyarthralgia and skin nodules was reported. Biopsy samples, which were obtained from her skin eruption exhibited dermal infiltration with histiocytes and multinucleated giant cells. Immunohistochemical staining indicated positivity for CD68. The patient was diagnosed with MRH and treated with a combination therapy of infliximab, prednisolone and methotrexate. Her symptoms improved markedly within 2 weeks. Following the results of this case study, a systematic review of 17 cases of MRH treated with tumor necrosis factor (TNF) antagonists was performed, and the efficacy of anti‑TNF treatment in MRH was analyzed.

Multicentric reticulohistiocytosis and fibroblastic rheumatism

Multicentric reticulohistiocytosis (MRH) and fibroblastic rheumatism (FR) are uncommon disorders with similar joint and skin manifestations. They are usually included among the non-Langerhans histiocytoses, but recent insights drive some criticism. The diagnosis is often challenging and must be confirmed by the histological typical features. If the skin manifestations are missing, the arthritic complaints may be confused with those of other rheumatic disorders. In these cases, only a careful clinical and radiological evaluation leads to the correct diagnosis. The natural course of the diseases may rapidly develop into disabling manifestations, making an aggressive treatment strongly recommendable. There is emerging evidence that anti-tumour necrosis factor-α agents and bisphosphonates are promising drugs for MRH, while a course of methotrexate and steroids seems to be the best option for FR. Finally, the clinician should be aware that in many cases MRH, but not FR, is associated with a large number of systemic manifestations and with malignancy. This eventuality must be accurately ruled out.