A 16-year-old female presented with a 3-week history of an asymptomatic papular eruption in her axillae with progressive increase in the number of lesions. The patient had no systemic symptoms. Personal and familial history was negative for cutaneous diseases. Examination revealed discreet and grouped yellow-red papules symmetrically in the axillae (Figure 1). Mucous membranes were not involved. Dermoscopy showed an orange-yellow background with an erythematous or brown rim. Some lesions had telangiectatic vessels and whitish globules (Figure 2, red arrows) and were crossed by white rail lines (Figure 2, asterisk). A biopsy was performed (Figure 3). Histopathological examination revealed a nodular polymorphous infiltrate expanding the papillary dermis composed of mononucleated and multinucleated histiocytes, most of which were Touton giant cells, xanthomatized cells, lymphocytes and scattered neutrophils and eosinophils (Figure 3). The histiocytes were epithelioid with a few scattered spindled cells. Immunohistochemistry was positive for CD45 and CD68 and negative for CD1a and S100 (Figure 4, CD68 staining). Laboratory work-up including serum triglycerides and cholesterol levels were normal. Magnetic resonance imaging (MRI) did not show involvement of the pituitary gland or hypothalamus. Upper respiratory or ocular involvement was not detectable. The patient declined therapy. She was monitored and had persistence of disease without new lesions at 3 months follow-up. Xanthoma disseminatum (XD) is a rare, usually normolipemic, non-Langerhans cell histiocytosis (non-LCH) of unknown origin, typically in patients between 5 and 25 years of age in 60% of cases, with a male: female ratio of about 2:1.1, 2 Clinically, XD is characterized by numerous yellow or red-brown papules and nodules, symmetrically distributed on the flexor areas and around the eyes.1 The lesions are initially isolated but over months may coalesce into plaques.2 Mucous membranes of the upper digestive and respiratory tracts can be affected.3 In about 40% of all patients, including both adult and pediatric cases, XD is associated with a mild or transient form of diabetes insipidus due to pituitary gland involvement.1-3 On dermoscopy, xanthogranulomatous lesions show yellow-orange background, sometimes surrounded by a subtle erythematous border and telangiectatic vessels known as the “setting sun” sign.4, 5 Longstanding lesions may present additional signs of fibrosis and regression, such as white streaks or white structureless areas.4, 5 These features have also been described in XD.5 Our patient had lesions with the “setting sun” sign but no signs of fibrosis or regression. White rail lines in some lesions corresponded to fibrous septa on histopathology and did not represent fibrotic or regressive manifestations of advanced lesion. The dermoscopic pattern of our patient's lesions was consistent with the short duration of the disease. Histopathologically, XD is characterized by a dense dermal infiltrate composed by histiocytes with irregular scalloped borders admixed with a variable number of foam cells, Touton giant cells and inflammatory cells. In some cases, as in ours, XD lesions may present scattered neutrophils and eosinophils; rarely they are conspicuous and in such a case they can be confused with LCH. The composition of the infiltrate varies depending on the timing of the biopsy with increased numbers of foam cells seen in more mature lesions. The immunochemical staining pattern in XD is similar to other non-LCH disorders, with histiocytes which exhibit positive staining for Factor XIIIa, particularly at the early stages, and CD68, CD163, fascin and CD14 and fail to stain with S-100, CD1a and CD207. The clinical differential diagnosis of XD includes disseminated juvenile xanthogranulomas (JXGs) and eruptive xanthomas (EX). JXG is the most frequent non-LCH, presenting as a spontaneously regressing, dome-shaped, yellow, red or brown papule or nodule, which usually appears at birth or early in life.4 JXGs typically arise on the head, neck and trunk, with no predilection for flexural areas, as in XD.6 JXGs usually appear as solitary lesions, but multiple and disseminated forms are described.6 Systemic involvement, including the eyes, liver, spleen and kidneys, may occur.6 EX are itchy, yellow-orange dermal papules, formed by dermal accumulation of lipid-laden macrophages as a consequence of severe hypertriglyceridemia (above 2000 mg/dL).7 Location of EX on extensor surfaces of the extremities, buttocks and shoulders, as well as the abnormalities of serum lipids levels may help to distinguish EX from XD and JXG. Dermoscopy alone cannot be used to distinguish disseminated JXGs, EX and XD as they have similar dermoscopic findings. EX may be easily differentiated from non-LCH disorders on histopathology, while JXG and XD may be indistinguishable from a histopathological point of view, and in these cases clinical presentation should guide the diagnosis. XD is usually resistant to therapy and may have an unpredictable course, with self-healing, persistence, or progression.2 In mild disease, observation or local physical therapies, such as laser therapy, cryotherapy, curettage and electrodessication and excision, may be chosen. In severe cases, systemic treatment with lipid-lowering agents, systemic corticosteroids and immunosuppressants have been attempted with mixed results.8 Generally, XD patients have normal serum lipid levels but lipid-lowering agents may be useful in these patients to reduce inflammation and production of foam cells.9 Not all lipid-lowering agents can be used in children, because some of them lack pediatric safety data. Cladribine is a synthetic purine analogue, which exerts antineoplastic effects inhibiting DNA synthesis and proliferation, and a promising therapy for XD.10 However, there can be severe adverse effects, such as myelosuppression, and there is a lack of sufficient data in its use in children. Recently, a XD patient with facial involvement has been successfully treated with narrowband UV-B phototherapy.11 This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.