Immunohistochemical classification of primary and recurrent macular corneal dystrophy
C. Cursiefen, C. Hofmann-Rummelt, U. Schlötzer-Schrehardt, D.-C. Fischer
Purpose: To evaluate the distribution of macular corneal dystrophy (MCD) immunophenotypes in Germany, to find out if a single immunophenotype carries an increased risk for recurrence and to examine whether the recently in Saudi Arabia discovered immunophenotype I A also occurs in Germany.
Methods: Indirect immunohistochemistry for keratan sulfate (KS) was performed on 44 corneal buttons of 37 patients with MCD obtained by perforating keratoplasty includig 2 recurrences (mAbs 3D12/H7, 4G4/A10 and 5-D-4). The serum concentration of KS was determined using mAb 5-D-4 in a serum antigen-inhibition assay in 7 patients. Immunogold labeling with the mAb 5-D-4 was performed in one cornea with immunophenotype I A.
Results: Indirect immunohistochemistry with mAb 5-D-4 demonstrated no reaction in 18 corneas of 16 patients (43 %; immunophenotype I), positive reactions solely within single keratocytes in 21 corneas of 16 patients (43 %; immunophenotye I A) and positive reactions in keratocytes, stroma, endothelial cells and Descemets membrane in 5 corneas of 5 patients (14 %; immunophenotype II). Serum levels of keratan sulfate were not detectable in patients with immunophenotypes I and I A and within normal limits in patients with immunophenotype II. Comparison of the results of mAbs 5-D-4 and 3D12/H7 showed that mAb 5-D-4 recognizes more epitopes on keratocytes, corneal endothelial cells and Descemets membrane than 3D12/H7. Immunogold labeling with mAb 5-D-4 in a cornea with immunophenotype I A localized KS mainly to the rough endoplasmic reticulum and in intracellular deposits of mucoid material with low electron density within keratocytes. The two recurrences demonstrated immunophenotype II (p<0.05). No positive reaction occurred with the mAb 4G4/A10 neither in normal cornea nor in MCD immunophenotypes I, IA and II (as classified with 5-D-4).
Discussion: Macular corneal dystrophy immunophenotype I A can be found outside Saudi Arabia in German patients. MCD-immunophenotypes I and I A have a much higher prevalence than immunophenotype II in German patients. Recurrences of MCD necessitating rekeratoplasty seem to be more common in immunophenotype II.
Department of Ophthalmology and University Eye Hospital,University of Erlangen-Nürnberg, D-91054 Erlangen