[Sclerosing mesenteritis: can it be a IgG4 dysimmune disease?].

AIMS: Mesenteric panniculitis (MP), sclerotic mesenteritis (SM) and mesenteric lipodystrophy (ML) are the three histopathological forms of a rare inflammatory mesenteric disease. The pathogenesis is unknown until now. Hypothesis of a dysimmune disorder is advocated. Our purpose was to find histological basis to assert this hypothesis.

MATERIAL AND

METHODS

All patients with a diagnosis of inflammatory mesenteric disease made in Beaujon hospital were selected. A histological study and a systematic immunostaining with IgG4, CD3 and CD8 antibodies were performed for each patient with paraffin block available. Dysimmune features were defined by: a plasma cells component >30 %, an eosinophilic polynuclears component >10 %, a rate TCD8/CD3 >30 % and IgG4+ plasma cells >30/high power field (x400). Cases were classified in 3 forms on the basis of the predominant component: MP (lymphoid/plasma cell infiltrate), SM (fibrosis), ML (fat necrosis).

RESULTS

Thirteen patients (7 men, 6 women) were selected, with a mean age of 57 years (21-80 years); a paraffin block was available for 10 patients. The clinical and histological presentations were heterogeneous: a mesenteric mass was the most frequent mode of revelation (6/13 patients) and all histological forms were present (3 MP, 5 SM and 5 ML). Nine patients had surgical biopsy, 2 had a trephine biopsy and 2 a resection. Standard histological analysis showed numerous eosinophils (> or =10 %) and plasma cells (>30 %) in respectively 3 (23 %) and 6 (46 %) of the 13 cases. The immunohistochemistry (performed in 10 patients) showed numerous TCD8+ in 80 % of the cases and numerous IgG4+ plasma cells in only 31 % of the cases (4 cases) (IgG4+ >30/x400).

CONCLUSIONS

Our results demonstrate that inflammatory mesenteric diseases are heterogeneous: high components of plasma cells, eosinophils and TCD8+ lymphocytes were found respectively in 46, 23 and 80 % of cases; eosinophils were observed exclusively in sclerotic forms. Only 31 % of cases encompass numerous IgG4+ plasma cells, suggesting a pathogenesis different than hyper-IgG4 diseases.