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This is a literature review of the use of Sirolimus, to treat orbital lymphatic malformations. Sirolimus is an immunosuppressant used in renal transplants, and acts by inhibiting mammalian target of rapamycin (mTOR), which in turn inhibits activation of T and B cells. The authors found nine reports with 10 cases of orbital lymphatic malformations treated with Sirolimus. There were four males and six females, aged between one week and 23 years. The malformations were purely lymphatic in six, lymphaticovenous in three and lymphatic-arteriovenous in one. Six patients had undergone previous treatments including surgery, sclerotherapy and other medical therapy. Five patients started therapy under the age of six years, and two after the age of 16 years. Dosing varied and was based on surface area in some reports and weight in others and ranged from six to 52 months in duration. Trough target levels were 5-20ng/ml and most patients remained within target. Interestingly, one patient who was below target responded but developed a recurrence. When restarted on Sirolimus at a dose which reached target she had a complete response. Overall, three patients had a complete response defined as disappearance of the lesion clinically or radiologically or complete resolution of symptoms. Seven had a partial response and none had no response. Adverse effects included mild reversible leukopenia, mildly elevated triglycerides or cholesterol, and mild transaminitis, none of which required cessation of Sirolimus. The article is interesting as it offers hope for an otherwise very challenging condition, particularly for predominantly microcystic sub-types which are not amenable to sclerotherapy. Unfortunately, details of the morphological subtype were missing in seven of the 10 patients. 

The use of Sirolimus for treatment of orbital lymphatic malformations: A systematic review.
Shoji MK, Shishido S, Freitag SK.
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James Hsuan

Aintree University Hospital, Liverpool, UK.

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