Sir,
A 7-month-old girl was referred to our department for pigmented lesions that had appeared one month after birth. The patient and her mother did not have any significant medical history. Physical examination revealed multiple brownish pigmented macules on the right head, face, chest, back and left lower limb [Figure 1]. Darier's sign was negative, and a biopsy was taken from the left lower limb. Histological examination of the biopsy showed pigmentation of the basal layer of the epidermis and dense mononuclear cell infiltration in the papillary dermis [Figure 2a]. Toluidine blue staining revealed a number of mast cell infiltration [Figure 2b], and Dylon staining revealed an increased number of eosinophils [Figure 2c]. In addition, immunohistochemistry results revealed IL-5 positive cells within the upper dermis [Figure 2d], and laboratory data showed peripheral blood eosinophilia (960 cells/mm3: normal <590). We diagnosed the eruptions as urticaria pigmentosa and followed up for three months without any treatment until the patient moved to another prefecture. Although the eruptions remained unchanged, the patient did not show any other symptoms during our follow-up period.
Figure 1.
A 7-month-old girl showed multiple brownish pigmented macules on the right head, face (a) (arrowhead), chest (b) and left lower limb (c)
Figure 2.
(a) Histological examination of the biopsy showed pigmentation of the basal layer of the epidermis and dense mononuclear cell infiltration in the papillary dermis (hematoxylin-eosin staining, original magnification × 200). (b) Toluidine blue staining revealed many mast cells within the infiltrating cells (original magnification × 200). (c) Dylon staining revealed an increased number of eosinophils (original magnification × 200). (d) Immunohistochemistry results revealed interleukin 5-positive cells within the upper dermis (original magnification × 400)
In this report, we showed a rare case of urticaria pigmentosa with eosinophilic infiltration in an infant. Urticaria pigmentosa, also known as maculo-papular cutaneous mastocytosis, usually shows generalized reddish-brown macules or papules.[1] A typical histopathologic finding is perivascular and interstitial infiltration of mast cells in the upper dermis. However, there are rare cases of urticaria pigmentosa accompanied by eosinophilic infiltration. To date, a few reports demonstrated that cutaneous mastocytosis was rarely accompanied by eosinophilic infiltration.[2,3] The mechanism of eosinophilic infiltration in patients with urticaria pigmentosa has not yet been elucidated. A possible mechanism is that mechanical stress induces eosinophilic infiltration, as well as urticaria (Darier's sign).[2] Mast cells contain a variety of cytokines and growth factors, and mechanical stress induces mast cell degranulation. Degranulated mast cells that release prostaglandin D2, platelet-activating factor, and interleukin 5 (IL-5) can promote eosinophilic infiltration in skin lesions.[4] Our case is unique because the patient also showed peripheral blood eosinophilia. To our knowledge, cases of urticaria pigmentosa accompanied by eosinophilic infiltration do not show peripheral blood eosinophilia. A previous study demonstrated that inhalation of IL-5 in patients of asthma leads to the development of peripheral blood eosinophilia.[5] In addition, T helper 2 cells that release IL-5 are activated by mast cells via the interleukin 4 pathway.[4] In the present case, we examined whether IL-5-positive cells increased in the skin lesions of urticaria pigmentosa associated with eosinophilic infiltration, and there were IL-5 positive cells within the upper dermis. Thus, IL-5 released from mast cells and/or T helper 2 cells can cause eosinophilic infiltration in urticaria pigmentosa. In conclusion, we demonstrated a unique case of urticaria pigmentosa, which showed eosinophilic infiltration in the skin lesions and peripheral blood eosinophilia.
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Conflicts of interest
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