Abnormal extracellular material in the levator palpebrae superioris complex in congenital ptosis
B. J. Clark, E. G. Kemp, W. M. Behan and W. R. Lee
Department of Pathology, Western Infirmary, Glasgow, Scotland.
OBJECTIVE: To determine the pathologic abnormalities of the levator
palpebrae superioris in congenital ptosis. METHODS: By means of light and
electron microscopy and immunohistochemistry, anterior levator tissue
specimen from 15 patients with congenital ptosis excised during routine
levator resections were examined. RESULTS: All specimens showed lack of
muscle fibers with endomysial and perimysial fibrosis and thickening of the
aponeurosis. In addition, in four of the 15 patients, an abnormal
extracellular material was present. By light microscopy this appeared as an
unusual amorphous material arranged in clumps and bands, and electron
microscopy showed it to consist of parallel coarse bundles of
fibrillogranular material. Collagen type III and fibronectin were
identified within this material by immunohistochemistry. There was no
detectable collagen types I, II, IV, V, VI, or VII or laminin, and the
material did not stain for actin, myosin, myoglobin, amyloid P component,
or amyloid A. CONCLUSIONS: In four of 15 samples of levator palpebrae
superioris from patients with congenital ptosis, we identified an unusual
amorphous extracellular material that stained positively for collagen type
III and fibronectin on immunohistochemistry. This novel material, which we
call "amorphocollagenoid," may represent a product of dysgenesis of the
levator tissues. The source and full composition of this material merit
further study.
