Unilesional self‐limited Langerhans cell histiocytosis: a case report and review of the literature

Self‐limited Langerhans cell histiocytosis (LCH) represents a rare, congenital, cutaneous form of LCH associated with a good prognosis. Only 35 cases of solitary lesion self‐limited LCH have been reported. Herein, we present an additional case in a 3‐month‐old boy who presented with an isolated pigmented nodule on his left posterior shoulder, which had been present since birth. Punch biopsy showed histopathologic features of LCH with positive CD1a and CD68 stains. Further examination and investigation showed no features of systemic involvement. The lesion spontaneously resolved within 2 months, and there has been no evidence of recurrence on follow up. As several cases of recurrence and complications have been reported in self‐limited LCH, we emphasize the need for long‐term, and perhaps indefinite, follow up for symptoms and signs associated with LCH in these patients.     

Extracellular signal‐regulated kinase activation of self‐healing Langerhans cell histiocytosis: A case report

A 3‐month‐old boy developed small papules on his trunk. After the papules increased in number, the patient was diagnosed with Langerhans cell histiocytosis based on the pathological findings. He was referred to our department for further examination. Upon initial examination, the papules and nodules were scattered on his back, abdomen and lumbar region. Because he did not present with any organ involvement except the skin, he was diagnosed with single‐system and skin‐limited Langerhans cell histiocytosis. Skin rashes were treated with a topical steroid and started regressing 3 months after onset. All papules disappeared 6 months after onset. In this boy, the Langerhans cell histiocytosis tumor cells expressed phosphorylated extracellular signal‐regulated kinases. In Langerhans cell histiocytosis, BRAF V600E and other genes are known to mutate to act as driver mutations in stem cells of the myeloid dendritic cell lineage. Consequently, extracellular signal‐regulated kinases are continuously activated, which contributes to Langerhans cell histiocytosis carcinogenesis.     

A case of congenital solitary Langerhans cell histiocytoma

A newborn baby boy was referred to the Paediatric Dermatology Unit with a solitary asymptomatic nodule overlying his right nasolabial fold. Complete physical examination, full blood count, serum chemistry, liver function tests and baseline imaging were unremarkable. Histopathological examination showed an atypical dermal infiltrate of mononuclear cells that stained positive with CD1a and S100. A diagnosis of congenital solitary Langerhans cell histiocytoma was made. The lesion completely resolved by 4 months of age. The baby is now 15 months old and repeat systemic evaluation has remained normal.     

Congenital Langerhans cell histiocytosis presenting in a 27‐week‐gestation neonate

Langerhans cell histiocytosis is exceedingly rare in premature infants, and the few cases reported suggest a poor prognosis with systemic involvement. We present a case of Langerhans cell histiocytosis limited to a single cutaneous lesion, presenting in a 27‐week‐gestation infant, which is the youngest gestational age of reported Langerhans cell histiocytosis cases. The lesion showed spontaneous resolution by 41 weeks corrected gestational age, and systemic involvement was absent, demonstrating a mild course of skin‐only Langerhans cell histiocytosis in a premature infant.     

Progressive nodular histiocytosis – rare variant of cutaneous non‐Langerhans cell histiocytosis

Progressive nodular histiocytosis is an extremely rare skin disease is clinically characterized by the coincidence of two distinct lesions, namely, superficial xanthomatous papules up to 5 mm and deep nodules and tumors 1–3 cm. Histologically the nodules represent spindle cell xanthogranulomas. We report a 24‐year‐old women with these findings. The distinction from other non‐Langerhans cell histiocytoses, in particular multiple juvenile xanthogranulomas, which may be more likely to show spontaneous remission, is somewhat unclear; patients with progressive nodular histiocytosis usually follow a serious and disfiguring clinical course.     

Co‐existence of Langerhans cell histiocytosis and reticulohistiocytosis with initial presentation of skull lesions: A case report

Langerhans cell histiocytosis (LCH) is a rare histiocytic disorder resulting from dysregulated clonal proliferation of Langerhans cells. Reticulohistiocytosis (RH) is another rare histiocytosis caused by the proliferation of histiocytes other than Langerhans cells. Co‐existence of LCH and RH in different organs and in the same skin area has not been reported. We present the case of a 20‐year‐old woman who initially had co‐existing bone LCH and cutaneous RH. After 1 year of chemotherapy with cytarabine, bone LCH significantly improved but cutaneous LCH developed in the same area where cutaneous RH was, resulting in hybrid LCH and RH of the skin. This unique history provides some evidence to support the theory that LCH and RH originate from the same stem cells and subsequently develop into hybrid LCH and RH of the skin in a cytokine environment influenced by chemotherapy. Repeat skin biopsies may be considered for adjusting treatment regimens in LCH patients whenever pre‐existing skin lesions progress.