Her whole face and body were confluent sheets of blanching erythema. No papules, no texture, and no scale. No epidermal component, just markedly increased dermal and subcutaneous blood flow.
She was a bright red elderly female with rigors and a distressed look on her face. Whispers of toxic shock syndrome circulated among the staff. Was a superantigen responsible for this?
Red but not hypotensive. Her cutaneous beds were vasodilated, but muscle and visceral vasculature had retained arteriolar tone, and therefore maintained a normal blood pressure.
Mast cells leave the bone marrow as immature mononuclear cell precursors. They take up residence in tissues where they mature. When a mast cell or basophil meets an appropriate stimulus, like IgE cross-linked on their cell surface, degranulation releases histamine and other vasoactive mediators. The result is cutaneous vasodilation, the most famous type of hypersensitivity reaction described by Gell and Coombs in the 1960s. But these mediators, they have other effects.
“Are you having trouble breathing?” We had a language barrier, but she nonetheless appeared to have difficulty answering a simple question. She wouldn't look you in the eye. Rather than answer, she would cry and squint.
In too much distress? Or is this histamine's effect on her neurons?
Histamine and friends.Mediated by normal vascular endothelium, the response in the cutaneous bed is vasodilation. Histamine directly causes contraction, not relaxation, of smooth muscle in tissue without endothelium. Such interfaces include the bronchiole and intestinal wall.
Mildly tachypneic, she was not wheezing on exam, and her expiratory phase was normal. Bronchiolar smooth muscle appears relaxed.
“Are you having any pain? Where is the pain?” She cannot answer. She is whimpering.
Crampy pain from contracting intestinal smooth muscle? Her abdominal exam was soft and flat. Unlike surgical peritoneal processes, dynamic causes to abdominal pain can have a benign exam.
“Any diarrhea?” Hypermotile small bowel shortens transit time and decreases absorption.
Dorsalis pedis pulse is bounding. Precordium is bounding. Her skin out to her fingers and toes, fire red and blanching.
Was she stung by something? What did she eat? A large piece of spoiled tuna? What new medication did she start?
She shakes her head, frowning and squinting.
Maybe it is not the time for a history. She is not ready for fact-finding. That can wait until after treatment.
Block and stabilize. We start with antihistamines and a dose of oral glucocorticoid. She receives anxiolytic medication, and from the hallway, she appears more comfortable. Our resident ventures back across the curtain to obtain more facts.
“She has had this multiple times before, sometimes after meals. She ate eggs this morning,” he said. “She takes cyproheptadine.”
He continues about dizziness and intermittent, stabbing chest pain of ultrabrief duration.
Her exam did not display bronchiolar smooth muscle constriction. The pain associated with this, like cardiac and esophageal muscle, is generally more a tightness or pressure in the chest. Not something stabbing. With a past medical history of coronary artery disease uncovered, I suppose we will do our diligence and register an ECG.
Her symptoms were better, and her ECG would later return: inferior ST elevation injury pattern.
What?! Did she rupture a plaque from the stress of her hypersensitivity reaction? Did peripheral vasodilation steal blood away from her coronary circuit?
What we have come to expect is atheromatous plaque narrowing the lumen of a coronary artery and then rupture of the less mature and less stable plaques. Luminal occlusion is completed by the addition of thrombus atop the disrupted atheroma, and downstream injury ensues. Is this what we are dealing with? Standard ACS?
There are, however, static vasculopathies other than atherosclerosis.
Arteriosclerosis is a hardening of the arteries proximal to the arteriole. The elastic and muscular media are replaced by fibrous tissue that will later calcify. Unlike atherosclerosis, the intima and lumen remain uninvolved, so forward flow is preserved. Hardened and less distensible arteries are common with age. And systolic hypertension ensues over years.
Arteriolosclerosis is the thickening of the media and intima of arterioles by hyaline deposition. It is the common finding in diabetics and hypertensives, and remains the pathology behind our term “microvascular disease.” Tortuous vessels with narrowed lumens course throughout the human body, and are visible at the bedside in one location: the retina. The narrowed arteriolar lumen is responsible for elevations in diastolic pressure and inadequate tissue oxygenation despite hypertension.
She has at least one, if not all three, of the static vasculopathies. And atop that today, she has a dynamic vasculopathy. We see it as fire in cutaneous vessels and constriction in coronary vessels.
The immediate treatment. With atheroma and hyaline deposition replacing normal endothelium, the response to histamine in the coronary vessel is not vasodilation as it is in cutaneous beds but rather smooth muscle constriction, vasospasm mirroring what would happen to bronchiolar and enteric interfaces. The next treatment then is to supply the mediator that normal endothelium would otherwise have offered.
Nitroglycerin. Her atypical pain would get better with nitroglycerin, and her ST segments improved. Her initial troponin returned at 2. She went to the cardiac catheterization laboratory to demonstrate plaque and chronic, static vasculopathy worst in the posterior descending artery. No lesion requiring a new stent. Her signs mediated by spasm of coronary vessels responding to histamine and friends liberated in the hypersensitivity reaction?
Allergic angina and the allergic MI were first described in the 1950s. The entity would later be termed Kounis syndrome in the 1990s when it was noted that a favorite locale for mast cells to make their home is the shoulder of a coronary plaque. It is believed that histamine is not alone in its orchestration of coronary ischemia; instead it is accompanied by other mediators like thromboxane, leukotrienes, and platelet activating factor. It is an elaborate interplay of mast cells, T-cells, macrophages, and the endothelium that can result not only in coronary spasm but also plaque rupture and thrombus formation, an interplay that researchers find is eerily similar to the terminal events in garden-variety, nonallergic ACS.
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