Abstract: 【Abstract】 A 9-year-old male child presented with red plaques on the left upper limb for more than 5 years without obvious subjective symptoms. Topical glucocorticoids and calcineurin inhibitors did not markedly improve his condition. Skin examination showed dark red map-like plaques with clear borders on the extensor side of the left upper limb, with a few white scales attached to the surface and satellite lesions at the edge. There were no obvious abnormalities in routine blood and urine tests or immunological examinations. Histopathological examination revealed dense infiltration of abundant lymphocytes and plasma cells in the upper and middle dermis, with some inflammatory cells infiltrating the fat septa and focal formation of lymphoid follicles; immunohistochemical study showed positive staining for CD3 in interfollicular regions, CD20 in the follicular center, and CD38 in plasma cells, as well as for IgG Kappa chain and IgG Lambda chain; periodic acid-Schiff staining and acid-fast staining both showed negative results. A diagnosis of childhood benign lymphoplasmacytic plaque was made. The patient was treated with topical halometasone cream once a day in the morning, topical tacrolimus ointment once a night, and oral traditional Chinese medicine for promoting blood circulation and removing blood stasis. After 6 months of follow-up, the skin lesions became slightly flat, slightly lighter in color, and no new lesions occurred. Treatment and follow-up were ongoing.

Key words: Lymphoplasmacytic plaque, Lymphocyte and plasma cell infiltration, Mucosa-associated lymphoid tissue lymphoma, Cutaneous plasmacytosis, Acral pseudolymphomatous angiokeratoma of children