Reduction in the number and size of islets. This changemost often is seen in type 1 diabetes, particularly with rapidly advancing disease. Most of the islets are small, inconspicuous, and not easily detected.
Fig. 20.26A ). They are most often seen type 1 diabetes at the time of clinical presentation.
Amyloid deposition within islets in type 2 diabetesbegins in and around capillaries and between cells. At advanced stages, the islets may be virtually obliterated (see
Fig. 20.26B ); fibrosis also may be observed. Similar lesions may be found in older nondiabetics, apparently as part of normal aging.
An increase in the number and size of islets, especially characteristic of nondiabetic newborns of diabetic mothers. Presumably, fetal islets undergo hyperplasia in response to the maternal hyperglycemia.
Diabetic macrovascular disease. The hallmark of diabetic macrovascular disease is accelerated atherosclerosis
Fig.20.26(A)Autoimmuneinsulitisinahumanpancreaticexplant.ArrowspointtoinflammationsurroundingisletofLangerhans,whilethesurroundingacinarstructuresareessentiallynormal.(Photograph provided by Dr. Martha Campbell-Thompson, JDRF Network for Pancreatic Organ Donors, University of Florida., Gainesville, Florida.) (B)Amyloidosisofapancreaticisletintype2diabetes.Amyloidosistypicallyisobservedlateinthenaturalhistoryofthisformofdiabetes, withisletinflammationnotedatearlierobservations.
affectingtheaortaandlarge-andmedium-sizedarteries.Exceptforitsgreaterseverityandearlierageatonset,atherosclerosisindiabeticsisindistinguishablefromthatinnondiabetics(Chapter10).Myocardialinfarction,causedbyatherosclerosisofthecoronaryarteries,isthemostcommoncauseofdeathindiabetics.Significantly,itisalmostascommonindiabeticwomenasindiabeticmen.Bycontrast,myocardialinfarctionisuncommoninnondiabeticwomenofreproductiveage.Gangreneofthelowerextremities,asaresultofadvancedvasculardisease,isabout100timesmorecommoninindividualswithdiabetesthaninthegeneralpopulation.Thelargerrenalarteriesalsoaresubjecttosevereatherosclerosis,butthemostdamagingeffectofdiabetesonthekidneysisexertedattheleveloftheglomeruliandthemicrocirculation,asdiscussedlater.
Hyalinearteriolosclerosis,thevascularlesionassociatedwithhypertension(Chapters10and14),isbothmoreprevalentandmoresevereindiabeticsthaninnondiabetics,butitisnotspecificfordiabetesandmaybeseeninolderadultswhodonotsufferfromeitherdiabetesorhypertension.Ittakestheformofanamorphous,hyalinethickeningofthewallofthearterioles,whichcausesnarrowingofthelumen(
Fig.20.27 ).Notsurprisingly,indiabeticpatients,itsseverityisrelatednotonlytothedurationofthediseasebutalsotothepresenceorabsenceofhypertension.