Wang Tao,Liu Yuehua,Zheng Heyi

To the editor: Histiocytoid Sweet’s syndrome (HSS) is an entity which has clinical features similar to typical Sweet’s syndrome (SS) but is distinguished by dermal infiltration of immature neutrophilic granulocytes. Herein, we report a case of HSS associated with rheumatoid arthritis (RA) and pleuritis. She initially responded to prednisone.

A 59-year-old Chinese woman presented with a sudden onset of fever and non-pruritic painful maculoerymatous skin lesions on her upper body 10 years ago. She reported similar symptoms on three prior occasions. The third occurrence was six months prior to current presentation. She was advised to take corticosteroids. The lesions initially resolved, but recurred soon after abrupt corticosteroid discontinuation. Past medical history was significant for a palpitation for 6 years and RA in her lower limbs for 8 years. Social and family medical histories were unremarkable. On physical examination, she had a fever (Tmax=38.9°C) and tender, non-pruritic, erythematous, round, raised, and edematous plaques diffusely scattered over the upper body. Plaques were different in size, and included pustules and peripheral vesiculation in several new lesions (Figure 1A).She had swollen ankles. An extensive blood evaluation was unremarkeable. Chest X-ray revealed a rare pleuritiswith effusion, which confined a pleurisy serofibrinous. Histological features revealed pustules and prominent edema of the upper dermis, accompanied with dense perivascular inflammatory infiltration(Figure 1B). The dermal infiltrate was negative for CD20, CD35, PAS, S-100, and CD1a, and positive for myeloperoxidase, CD45, CD68 (KP1 and PGM1), with the reaction of KP1 antibody was much stronger than that of PGM1, antitrypsin alpha-1 antibody, alpha-1 antichymotrypsin, and lysozyme, indicating a myelocytic origin. Ki-67 staining showed no positive cells. The morphologic resemblance of these immature myeloid precursors to histiocytes was consistent with HSS. Given the diagnosis, the patient was given oral prednisolone 40 mg/d, and slowly tapered down. All of the skin lesions improved within two months and did not recur in a follow-up period of 4 years. The RA and pleuritis were well response to corticosteroids.

Our patient was found to have HSS with RA and pleuritis. HSS accompanied with RA had been reported before.According to clinical features and imaging signs, and this patient had an elevated erythrocyte sedimentation rate, RA, and the pleuritis was well response to corticosteroids, all of this suggest a diagnosis of rheumatoid pleuritis. However, we cannot rule out other type of pleuritis, etc. tuberculosis, without a histopathological proof. The relationship between HSS and pleutitis need more cases and further study.

All SS patients do not need to be treated because some patients have self-limited episodes. Systemic corticosteroids are the gold standard of therapy for SS,but other reported treatments include indomethacin, naproxen, cyclophosphamide, dapsone, potassium iodide, colchicines, etanercept,intravenous immunoglobulin, and clofazimine. Recurrence is very common. Wu et alreported a case of HSS following a course of trimethoprim-sulfamethoxazole (TMP-SFX). One month after discontinuation of TMP-SFX, the erythematous nodule spontaneously regressed. In our case, the patient refused treatment for RA and pleuritis, but was willing to take 40 mg/d prednisolone. Her HSS regressed completely without recurrence with a tapered treatment regimen and rheumatoid symptoms had improved.

In conclusion, we present a novel case of HSS associated with RA and pleuritis, which response to corticosteroids. In concordance with previously cited literature, we conclude that HSS is a new subtype of SS and SS treatments can be transferred to that of HSS.