Transmission electron microscopy of collagen dermal fibrils. A: Normal control. Fibril diameter is 97,1 +/- 8,1 nm (original magnification 45.000x). B: EDS arthrochalasis subtype (VIIB): complete retention of the N-propeptide of the α2(I)-procollagen chain is caused by skipping of the N-proteinase cleavage site itself, resulting in incorporation of pN-collagen molecules into the collagen fibrils in the extracellular matrix. This causes loss of the normal collagen fibril morphology, with decreased fibril density, decreased fibril diameter (43.82 +/- 6.09 nm), irregular contours and occasional cauliflowers (original magnification 45.000x). C: OI/EDS-proband P3: The N-proteinase cleavage site remains intact, but processing of the type I procollagen N-propeptide is delayed, resulting in abnormal collagen fibrils, with irregular borders and diameters (73.01 +/- 5.88 nm) that are smaller than those from controls but larger than for patients with EDS arthrochalasis type. Fibril contours are only slightly irregular and fibril density is decreased (original magnification 45.000×).