Systemic vasculitides may be classified according to the type of cells involved in the proliferation, as well as the specific type of tissue damage occurring within the vein or arterial walls. Under this classification scheme for systemic vasculitis, Kawasaki disease is considered to be a necrotizing vasculitis (also called necrotizing angiitis), which may be identified histologically by the occurrence of necrosis (tissue death), fibrosis, and proliferation of cells associated with inflammation in the inner layer of the vascular wall.Other diseases involving necrotizing vasculitis include polyarteritis nodosa, granulomatosis with polyangiitis, Henoch–Schönlein purpura, and eosinophilic granulomatosis with polyangiitis.Kawasaki disease may be further classified as a medium-sized vessel vasculitis, affecting medium- and small-sized blood vessels, such as the smaller cutaneous vasculature (veins and arteries in the skin) that range from 50 to 100 µm in diameter. Kawasaki disease is also considered to be a primary childhood vasculitis, a disorder associated with vasculitis that mainly affects children under the age of 18. A recent, consensus-based evaluation of vasculitides occurring primarily in children resulted in a classification scheme for these disorders, to distinguish them and suggest a more concrete set of diagnostic criteria for each. Within this classification of childhood vasculitides, Kawasaki disease is, again, a predominantly medium-sized vessel vasculitis.It can also be classed as an autoimmune form of vasculitis. It is not associated with anti-neutrophil cytoplasmic antibodies, unlike other vasculitic disorders associated with them (such as granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis). This form of categorization is relevant for appropriate treatment.
The pituitary stalk (also known as the infundibular stalk, Fendersons funnel, or simply the infundibulum) is the connection between the hypothalamus and the posterior pituitary. The floor of the third ventricle is prolonged downward as a funnel-shaped recess—the infundibular recess—into the infundibulum, where the apex of the pituitary is attached. It passes through the dura mater of the diaphragma sellae as it carries axons from the magnocellular neurosecretory cells of the hypothalamus down to the posterior pituitary where they release their neurohypophysial hormones, oxytocin and vasopressin, into the blood. This connection is called the hypothalamo-hypophyseal tract or hypothalamo-neurohypophyseal tract. Damage to the pituitary stalk blocks the release of antidiuretic hormone, resulting in polydipsia (excessive water intake) and polyuria (excessive urination). The diameter of the pituitary stalk at the level of optic chiasm is 3.3 mm, and at the pituitary gland insertion site is measured at 1.9 mm. See also
Pituitary stalk interruption syndrome

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