USMLE® Step 1 style questions USMLE
A 3-year-old boy is brought to the emergency department by his parent due to a fever for the past six days. The fever has not responded to treatment with acetaminophen. His parent mentions that the patient has refused to eat due to pain in his mouth. During his bath yesterday, the parent also noticed that he has a rash covering his trunk and limbs. Temperature is 39°C (102.2°F), pulse is 125/min, and blood pressure is 90/55 mm Hg. Examination shows an irritable-appearing child with a polymorphous rash covering the trunk which peels off near the fingers, as well as bilateral eye injection without exudate. Cervical lymphadenopathy is present. Which of the following complications may be seen in this patient if left untreated?
Kawasaki disease exam links
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Hannah Goerner, Tanner Marshall, MS, Jerry Ferro, Kyle Slinn, RN, BScN, MEd
Kawasaki disease isn’t at all related to the motorcycle and engine company, other than the fact that they were both founded or first described in Japan. Kawasaki disease is a vasculitis or an inflammation of the blood vessels, that mostly affects the coronary arteries but can also affect any large- or medium-sized arteries as well. With Kawasaki disease, the immune system attacks the arteries. Ultimately, it’s not quite known why this happens though, some theories suggest it has some infectious cause, though autoimmune reactions and genetic predisposition probably play a part as well.
Whatever the case, when the endothelial cells in the blood vessels are attacked, they become damaged which exposes the underlying collagen and tissue factor found in the middle layer of the blood vessel, or the tunica media.
And this leads to a few serious problems: First, these exposed materials increase the chance of blood coagulation. When blood coagulates it forms clots that can block blood flow in the coronary arteries, leading to ischemia of the heart muscle.
Secondly, damaged endothelial cells in coronary arteries mean weak artery walls, which can lead to coronary aneurysms. These aneurysms form because fibrin is deposited into the blood vessel wall as part of the healing process. Fibrin makes the vessel stiffer, less elastic, and unable to gently stretch with high arterial pressures; instead, the arteries develop permanent bulges that we call aneurysms. Aneurysms 8mm or larger are at the most risk of rupturing, which reduces blood flow to the heart, causing ischemia and potentially myocardial infarction, or heart attack.
And third, in some cases, the fibrosis doesn’t lead to aneurysms, but instead, the fibrosis of the blood vessel walls make the vessel walls thicker, which reduces the lumen diameter and restricts blood flow. If blood flow’s restricted or reduced, the heart again might become ischemic, leading to a heart attack.
Kawasaki disease is most commonly seen in infants and children under five years old and is more likely to affect boys. This disease is self-limited which means that the inflammation will resolve after 6 to 8 weeks but if we left it untreated, there is a 20-25% risk of the heart complications we went over.
Alright, so let’s look at the symptoms of Kawasaki disease. We rarely see any cardiac symptoms in the first few weeks unless the patient has an underlying heart condition already, and so cardiac symptoms typically evolve later.
Now the classic symptoms of Kawasaki disease are as follows: conjunctivitis with limbus sparing (which is red eyes with a margin right around the iris that is still white), a rash that might extend across other parts of the body, and starts polymorphous but later desquamates, or flakes off, adenopathy, or enlarged lymph nodes, especially the cervical lymph nodes. A strawberry tongue which is when the top layer of cells on their tongue slough off giving the tongue a very red, “strawberry” like appearance, also their mouth and throat may look really red too and their lips might become dry and cracked. Their hands and feet might get swollen and develop a rash as well. And finally, they might have 5 or more days of high fever that typically doesn’t resolve with antipyretics.
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "Kawasaki disease: etiopathogenesis and novel treatment strategies" Expert Review of Clinical Immunology (2016)
- "Diagnosis of Kawasaki disease" International Journal of Rheumatic Diseases (2017)
- "Diagnosis and management of kawasaki disease" Am Fam Physician (2015)