LCH is a rare clonal disease of the monocyte-macrophage system characterized by uncontrolled proliferation and accumulation of CD1a+/CD207+ dendritic cells [7]. The clinical behavior of LCH is remarkably heterogeneous and may range from isolated, self-healing skin and bone lesions to life-threatening multi-system condition.
Generally, patients with LCH can be divided into two groups based on the extent of involvement at diagnosis, namely, single-system LCH and multisystem LCH. The single-organ involvement may be unifocal or multifocal. Specific organs are considered high risk; they include the liver, spleen and hematopoietic system. Approximately 65% of patients have single-system disease [8]. Bone is the most common single-organ site (80% of cases) followed by the skin (12%) [9].
Congenital self-healing reticulohistiocytosis (CSHRH) is characterized by absence of systemic symptoms and spontaneous involution. In addition, dermatological manifestations are peculiar compared to the other LCH types. More than 100 cases have been reported in literature. This disease is probably underestimated due to the lack of extracutaneous involvement and spontaneous resolution within few weeks or months.
The most common presentation is characterized by diffuse multiple erythematous to purpuric-brown papulonodules or vesicles on the skin. In addition, cutaneous blisters and mucous erosions are very rarely reported. Indeed, although some authors have emphasized the absence of mucous membrane involvement, oral lesions have been described in five patients within the first days of disease manifestation [4, 10, 11]. Our patient presented since birth cutaneous blisters and few erosions in the oral mucosa without feeding difficulties [12]. Isolated lesions have been reported approximately in 25% of cases without preferred site; the disease onset is usually at birth, and in some cases within early childhood [13]. Few patients with CSHRH manifested at birth numerous blue-purplish and dark-red papular, nodular lesions; this presentation is considered part of the spectrum of blueberry muffin baby (BMB) [3]. Other rare and atypical cutaneous manifestations in children with CSHRH are diffuse hypopigmented flat-topped papules [14].
Differential diagnoses of CSHRH should consider: congenital or acquired infections (syphilis, impetigo, herpes, staphylococcal scaled-skin syndrome, etc.), autoimmune diseases (neonatal pemphigus or neonatal lupus erythematosus) or other haematological disorders [12].
Upon literature review, the most frequent sequela of CSHRH is post-inflammatory hyper- or hypopigmentation. Residual scars, milia, and anetoderma, especially in larger lesions are also reported [15]. Indeed, our patient presented dyschromic and atrophic scars on the trunk and right leg (Fig. 1C).
The diagnosis of LCH is based on histopathology and immunohistochemistry, which are the same in all forms of LCH. The hallmark cells stain positive for S100 protein, CD1a and Langherin (CD207), a monoclonal antibody direct against a type II transmembrane c-type lectin protein of Birbeck granules [16]. The activating BRAFV600E mutation has been recently identified as a frequent molecular genetic alteration both in systemic LCH and in CSHRH. The presence of circulating cells carrying the mutation is considered predictive of disseminate disease [17]. In our patient BRAFV600E mutation was present only on Langerhans cells of the skin.
The diagnosis of CSHRH is confirmed through clinical features, absence of extracutaneous involvement, early spontaneous healing, and histology. Moreover, relapse of cutaneous manifestation and/or subsequent visceral involvement including lungs, eyes, or bones have been described, especially in the first year of life. These data suggested that a long-term follow-up is mandatory [3, 5, 6, 18,19,20].
No specific treatment for congenital self-healing reticulohistiocytosis is required, apart from topical management for blisters and erosions as in our patient, or systemic antibiotics in case of bacterial superinfection [18].
In conclusion, our case confirms that congenital lesions of oral mucosa in CSHRH are possible. In our opinion this localization is probably underestimated due to fugacity of the erosions and difficulties in exploring the oral cavity in a newborn with normal feeding. Patients affected with LCH, without extracutaneous involvement who manifest a benign course require a follow-up until the first year of life because the diagnosis of CSHRH can be confirmed only a posteriori.
