Ingravallo G.
Department of Pathology, “Policlinico di Bari”, A. Moro University, Bari, Italy

Keywords: xanthoma, histiocytosis, child.

Case report. A 17-month-old girl was examined for the appearance of multiple small skin lesions located predominantly on the trunk. Family history was devoid of significant problems, apart from a history of allergic rhinitis in the father and allergic contact dermatitis in the mother. There were no relevant diseases in the remote personal medical history. The mother reported that for two weeks in full well-being, small asymptomatic lesions had appeared on the trunk. Dermatological examination highlighted 7 monomorphic, 1 mm diameter, yellowish papules, 3 of which in the left paravertebral region at the height of C7 (Fig. 1), 1 in the right preauricular region, 1 on the left side and 2 on the buttocks. Dermoscopic examination highlighted the homogeneous yellow color of the lesions (Fig. 1, box). Laboratory tests, including the lipid profile, were within normal limits. We performed a punch biopsy of the largest papule of the paravertebral region. The histological examination highlighted a widened dermal papilla with a thinned epidermis in the center and hyperplastic on both sides. The papillary dermis was completely occupied by a monomorphic cell population going down to the high-est part of the reticular dermis (Fig. 2). The infiltrate was made up of histiocytes with a central nucleus and large cytoplasm, most of the time foamy; only two giant cells of the Touton type were appreciated; an inflammatory infiltrate was practically absent (Fig. 3). Clinical and histological data led to the diagnosis of papular xanthoma. Parents were reassured about the benignity of the disease and its probable spontaneous regression.

Fig. 1: Papular xanthoma: yellowish papules, with yellow color more evident on dermoscopy (inset).

Discussion. Papular xanthoma belongs to Class II - non-Langerhans histiocytosis with dermal dendrocytes - along with juvenile xanthogranuloma and other less frequent forms (3). Papular xanthoma mainly affects the child (1, 2), but it can also affect the adult (5).
Our case adheres to the criteria proposed by Winkelmann (5) for papular xanthoma, i.e. 1- asymptomatic papules distributed throughout the skin, 2- absence of visceral involvement, 3- normal lipid profile, 4- infiltrate composed mainly of foam cells, 5- absence of one initial histiocytic phase and inflammatory infiltrate. From a clinical point of view (2) the lesions appear in the first year of life in a progressive way for some months, mainly affecting the back and face, always sparing the palmar-plantar region and mucous membranes; their number varies, but they can usually be counted, and their diameter is also variable, the smallest being of 1 mm, the largest rarely exceeding 1 cm. These are yellow lesions from their appearance, which spontaneously regress in months, sometimes years (4). Mucous membranes and internal organs are always spared and the lipid profile is normal.
Papular xanthoma enters differential diagnosis with numerous conditions. Juvenile xanthogranuloma is difficult to differentiate from a clinical point of view, except in cases where physical examination or at least the history highlights a prexanthomatous phase; histologically the presence of numerous Touton cells and inflammatory infiltrate speaks in favor of the diagnosis of juvenile xanthogranuloma. Disseminated xanthoma is clinically characterized by greater polymorphism, with the presence of papules, nodules; the lesions converge in the axillary and inguinal folds giving rise to more or less extensive plaques; lesions of other organs such as the eye, mucous lesions and often pitressin-sensitive diabetes coexist. Benign cephalic histiocytosis differs histologically due to the lack of foam cells.
Conclusion. The current case was presented because of its rarity and to remind doctors of the existence of this benign histiocytosis which allows the family to be reassured.

Conflicts of interest
The Author declares that he has no conflicts of interest.

Address to: Prof. Ingravallo G.
Department of Pathology, Policlinico di Bari
Piazza G. Cesare, 11, Bari, Italy

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