Coexistence of pyoderma gangrenosum and sweet's syndrome in a patient with ulcerative colitis

Pyoderma gangrenosum (PG) and Sweet's Syndrome (SS) are inflammatory skin diseases caused by the accumulation of neutrophils in the skin and, rarely, in internal organs. These neutrophilic dermatosis (NDs) are distinguished by the existence of forms of transition or overlap. They are frequently associated to systemic diseases especially hematologic and gastrointestinal ones. We report a case of a patient with ulcerative colitis (UC) who successively developed two types of NDs: PG then SS. A 66 years old patient with a history of UC consulted in July 2012 for an erythematous swelling of the back of the right hand treated with antibiotics without improvement. At that time, bacteriological samples were negative. In October 2012, he was hospitalized for polyarthralgia and impaired general condition. In physical examination, he had vesiculobullous plaque of 10 cm long of the right hand and wrist, infiltrated erythematous plaque on the right leg and another topped with a large pustule at the left ankle. Skin biopsy showed at the back of the right hand an aspect of PG and at the infiltrated plaques of the ankle an aspect of SS. Prednisone was started with improvement of the skin lesions and a recovery condition. The combination of PG and SS has already been described in cases of hematologic malignancy and rarely in UC. There is also the notion of passage from a neutrophilic dermatosis to another. Indeed, a typical lesion initially of SS can evolve to a future PG. This case demonstrates that neutrophilic dermatoses form a continous spectrum of entities that may occur in UC.


Introduction
Neutrophilic dermatoses (NDs) are characterized histologically by an epidermal and/or dermal infiltrate of polymorphonuclear leucocytes, absence of microorganisms on special stains and culture. This group of diseases includes, Sweet´s syndrome (SS), pyoderma gangrenosum (PG), erythema elevatum diutinum, neutrophilic eccrine hidradenitis and Sneddon Wilkinson disease [1]. Recently, NDs have been included among the autoinflammatory diseases, which are due to mutations of genes regulating the innate immune responses [2]. These entities are distinguished by the existence of forms of transition or overlap and the frequency of their association with systemic diseases especially hematologic and gastrointestinal ones. We report a case of a patient with ulcerative colitis (UC) who successively developed two types of NDs: PG then SS.

Patient and observation
A 66 year old patient with a history of UC treated by mesalazine since 5 years consulted in July 2012 for a painful erythematous swelling of the back of the right hand. The bacteriological samples were negative, the lesion was considered as an abscesses and the patient was treated with antibiotics and local antiseptics without improvement. The evolution was characterized by the appearance of an erythematous vesiculobullous centrifugal expansion taking the whole back of the right hand treated several times by various antibiotics unsuccessfully. Biopsy of this lesion was initially not specific. In October 2012, the patient was hospitalized for fever and polyarthralgia in the context of impaired general condition. He had a quiescent UC disease.
The skin examination found an erythematous plaque of 10 cm of diameter, with a raised border and vesicules, taking the back of the right hand and wrist (Figure 1) . There was also an infiltrated erythematous plaque on the right leg (

Discussion
SS and PG are the most common neutrophilic dermatosis. They have many features in common: neutrophilic infiltrate, altered immunologic reactivity, response to immunosuppressives and reports of coexistence in a single patient [3]. The combination of these two entities has already been described in cases of hematologic and much more rarely in the case of chronic inflammatory bowel disease [4] .In fact , there is an overlap between the two conditions with lesions categorised as SS actually being clinically more characteristic of atypical bullous PG and vice versa [3]. Indeed, a typical lesion initially of SS can evolve to a future PG.
Other associations of NDs have been reported: PG and subcorneal pustular dermatosis [5], PG and aseptic spleen abscess [6]. We are actually dealing with a "neutrophilic disease". Our observation showed that neutrophilic dermatoses are a continous spectrum as our patient developed first PG followed by SS. Unlike PG, the incidence of which, in UC patients, is about 1-3% [2], SS is very rare. The increasing number of patients affected by intestinal bowel diseases (IBD) developing SS during the last years, together with the evidence that cutaneous manifestations of IBD are very frequent, would appear to suggest that there is a relationship, possibly a common pathogenetic mechanism, between IBD and SS. Although NDs have been described also in some patients with quiescent IBD, the occurrence of the disorder has frequently been reported during relapse of disease. The patient described here had a quiescent disease when the NDs had occurred.
In histological samples, the lack of vasculitis and the abrupt onset of dermatosis without ulcerations allow the SS to be dinguished from PG. Malone et al suggested that vasculitis may be present in some patients with Sweet's syndrome. It is than an epiphenomen due to the release of noxious products from neutrophils, especially in the Page number not for citation purposes 3 cases of lesions of long duration [7]. In our patient, histology was typical for PG and SS without vasculitis in the second one.
Concerning the treatment of NDs, usually four to six weeks of glucocorticoid therapy are needed [2]. Agents that have been successfully implemented as glucocorticoid-sparing agents include dapsone, azathioprine [8,9], tacrolimus, mycophenolate mofetil, methotrexate, chlorambucil, and clofazimine [2]. Tumor necrosis factor-α inhibitors, such as adalimumab or infliximab, have been shown to be helpful with refractory disease, especially in patients with inflammatory bowel disease [10]. SS and PG are usually responsive to oral corticosteroids, and the immunosuppressant should be considered in resistant or highly relapsing cases. In our case, the UC was quiescent so our patient was treated with corticoids alone with a good clinical and biological evolution.

Competing interests
The author's declare no competing interests.

Authors' contributions
All authors contributed significantly to this work.