Summary Auto‐reactive cytotoxic T lymphocytes play a key role in the progressive loss or destruction of melanocytes in vitiligo but the mechanism underlying the loss of self‐tolerance is unknown. A deregulation of regulatory T‐cell biology has recently been suggested. The analysis of the suppressive effects of peripheral T regulatory cells in vitiligo patients revealed a functional defect in seven of 15 cases. This defect was strongly correlated with disease activity. The evaluation of the percentage of peripheral regulatory T lymphocytes did not reveal any intrinsic quantitative defect. Yet, a decrease in the percentage of such cells was noted in patients with progressive forms, suggesting a recruitment of regulatory T cells from the peripheral blood to the site of injury. This was further corroborated by the significant increase of Forkhead box P3 expression in the vitiliginous skin of patients. Our data support the involvement of a functional defect of peripheral regulatory T cells in the pathogenesis of vitiligo and open new possibilities to advance therapeutic approaches.

Our results indicate that effector T lymphocytes from active CD become resistant to suppression by Tregs. This resistance might cause loss of tolerance to gluten, but also to self-antigens.

Painless unilateral proptosis is a frequent manifestation of numerous orbital neoplastic and non neoplastic processes. Various mesenchymal tumours of both fibrohistiocytic and vascular origin are well-described causes. Hemangiopericytomas (HPC) are rare vascular tumours which can infrequently involve the orbit and their incidence is estimated to be 0.8% to 3% of primary orbital tumours 1,2 . We herein report a new case of orbital HPC revealed by unilateral proptosis in a 38-year-old man. Our aim was to highlight the clinicopathological and radiological features of this rare neoplasm with review of the current literature. CASE REPORTA 38-year-old previously healthy man, presented with a onemonth history of rapid expanding intra-orbital mass resulting in painless proptosis of the left eye. On admission, ophthalmologic examination revealed severe left eye proptosis (grade III). A palpable mass in the left orbit was protruding out of the palpebral fissure (Figure 1). It was irreductible, non-tender and nonpulsatile. The conjunctiva was chemotic and there was marked ulcerative keratitis. The visual acuity was 0 / 10 in the affected eye and ocular movements were restricted in all directions. The contralateral eye was within normal limits. Computed tomography (CT) scan of the orbital region (Figure 2) revealed a 87 x 54 x 32 mm, well-circumscribed mass within the intraconal space of the left orbit extending along the optic nerve and homogeneously enhanced after intravenous administration of contrast medium. Magnetic resonance imaging (Figure 3) showed a soft tissue mass iso-intense on T1-weighted images and hypo-intense on T2-weighted images. Laboratory tests and chest radiograph were within normal limits. An incisional biopsy of the intra-orbital mass was performed but was difficult to realize due to excessive haemorrhage. Histological examination of the tiny biopsy specimen obtained, established an initial diagnosis of an undifferentiated sarcoma. Orbital exenteration was carried out due to the infiltrative and highly vascular nature of the tumour.Macroscopically, the exenteration specimen measured 130 x 120 x 105 mm. A small atrophic globe at the anterior aspect of the specimen did not appear invaded by the tumour. The cut section of the mass showed a firm greyish white tumour. The eyelids were not infiltrated by the tumour. Histological examination of the surgical specimen showed a hypercellular neoplasm predominantly composed of randomly oriented polygonal and rounded cells with ill-defined cytoplasm

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