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B.K. Wabbels, J.A. Schroeder, B. Voll, H. Siegmund, B. Lorenz; Electron Microscopic Findings in Levator Muscle Biopsies of Patients With Isolated Congenital or Early–onset Acquired Ptosis . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5727.
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Purpose: Systemic mitochondrial diseases as chronic progressive external ophthalmoplegia (CPEO) often cause ptosis. We wanted to know whether mitochondrial abnormalities in the levator muscle are the underlying cause in some patients with isolated congenital or acquired ptosis with otherwise no clinical signs of mitochondriopathy. Methods: Included in this study were 40 patients who underwent ptosis surgery for congenital ptosis (group 1, 21 patients) or isolated acquired ptosis in youth or early adulthood (age of onset 3–51 years, group 2, 19 patients). All patients had a thorough clinical examination before and after surgery. Biopsies of levator and/or orbicularis oculi muscle were performed by one surgeon (BL) at surgery (resection of levator muscle or frontalis suspension). Ultrathin sections were examined with transmission electron microscopy (LEO912AB). The findings were compared with levator muscle biopsies from 4 patients with CPEO and 2 patients with traumatic ptosis or pseudoptosis with enophthalmos (negative controls). Results: 28 samples of 24 patients could be further evaluated (11 patients of group 1, 13 of group 2). In the others not enough striated muscle fibers were present. Six patients of group 1 and 8 patients of group 2 had typical signs of mitochondriopathy such as megamitochondria, swelling and abnormal cristae as the CPEO patients. No mitochondrial pathology was seen in the control group. Levator function was in mean 7.2 mm (4–10 mm) in group 1 and 12.7 mm (9–15 mm) in group 2. No significant clinical differences could be found between the patients with and without mitochondrial abnormalities in both groups. Conclusions: Our results indicate that mitochondrial alterations may be an etiologic factor also in isolated congenital or early–onset acquired ptosis, as electron microscopic findings in levator muscle biopsies showed local mitochondriopathies in a substantial proportion of cases. One patient with mitochondriopathy developed EMG changes in the frontalis muscle since surgery, so it could be presumed that in some patients ptosis may be the first sign of a generalized mitochondriopathy and electron microscopy examination would be of prognostic value.
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