Page 407 - Textbook of Pathology, 6th Edition

hyperplastic arteriolosclerosis and necrotising arteriolitis. All 391
the three types are common in hypertension but may occur
due to other causes as well.

Hyaline Arteriolosclerosis
Hyaline sclerosis is a common arteriolar lesion that may be
seen physiologically due to aging, or may occur pathologically
in benign nephrosclerosis in hypertensives and as a part of
microangiopathy in diabetics; the subject is discussed again
in Chapter 22.

MORPHOLOGIC CHANGES. The visceral arterioles are
particularly involved. The vascular walls are thickened
and the lumina narrowed or even obliterated.
Microscopically, the thickened vessel wall shows
structureless, eosinophilic, hyaline material in the intima
Figure 15.1 The structure of a medium-sized muscular artery. and media (Fig. 15.2,A).
PATHOGENESIS. The exact pathogenesis is not known.
ARTERIOSCLEROSIS However, the following hypotheses have been proposed:
Arteriosclerosis is a general term used to include all condi- i) The lesions result most probably from leakage of compo-
tions with thickening and hardening of the arterial walls. nents of plasma across the vascular endothelium. This is
The following morphologic entities are included under substantiated by the demonstration of immunoglobulins,
arteriosclerosis: complement, fibrin and lipids in the lesions. The permeability
I. Senile arteriosclerosis of the vessel wall is increased, due to haemodyanamic stress CHAPTER 15
II. Hypertensive arteriolosclerosis in hypertension and metabolic stress in diabetes, so that these
III. Mönckeberg’s arteriosclerosis plasma components leak out and get deposited in the vessel
(Medial calcific sclerosis) wall.
IV. Atherosclerosis ii) An alternate possibility is that the lesions may be due to
The last-named, atherosclerosis, is the most common and immunologic reaction.
most important form of arteriosclerosis; if not specified, the iii) Some have considered it to be normal aging process that is
two terms are used interchangeably with each other. exaggerated in hypertension and diabetes mellitus.

SENILE ARTERIOSCLEROSIS
Hyperplastic Arteriolosclerosis
Senile arteriosclerosis is the thickening of media and intima
of the arteries seen due to aging. The changes are non- The hyperplastic or proliferative type of arteriolosclerosis is
selective and affect most of the arteries. These are possibly a characteristic lesion of malignant hypertension; other The Blood Vessels and Lymphatics
induced by stress and strain on vessel wall during life. causes include haemolytic-uraemic syndrome, scleroderma
and toxaemia of pregnancy.
MORPHOLOGIC FEATURES. The changes are as under: MORPHOLOGIC FEATURES. The morphologic changes
1. Fibroelastosis: The intima and media are thickened due affect mainly the intima, especially of the interlobular
to increase in elastic and collagen tissue. arteries in the kidneys. Three types of intimal thickening
2. Elastic reduplication: The internal elastic lamina is split may occur.
or reduplicated so that two wavy layers are seen. i) Onion-skin lesion consists of loosely-placed concentric
Eventually, the fibrotic changes result in age-related layers of hyperplastic intimal smooth muscle cells like the
elevation of systolic blood pressure. bulb of an onion. The basement membrane is also
thickened and reduplicated (Fig. 15.2, B).
HYPERTENSIVE ARTERIOLOSCLEROSIS ii) Mucinous intimal thickening is the deposition of amor-
phous ground substance, probably proteoglycans, with
Hypertension is the term used to describe an elevation in scanty cells.
blood pressure. Pathology of 3 forms of hypertension— iii) Fibrous intimal thickening is less common and consists
systemic, pulmonary and portal, is discussed in detail with of bundles of collagen, elastic fibres and hyaline deposits
diseases of the kidneys (Chapter 22), lungs (Chapter 17) and in the intima.
liver (Chapter 21) respectively. Severe intimal sclerosis results in narrowed or
Arteriolosclerosis is the term used to describe 3 morpho- obliterated lumen. With time, the lesions become more
logic forms of vascular disease affecting arterioles and small and more fibrotic.
muscular arteries. These are: hyaline arteriolosclerosis,