Multiple sclerosis manifests as asymmetrical and in different parts of the body because:

Correct Answer: A

Rationale: The correct answer is A. Multiple sclerosis is characterized by the immune system attacking the myelin sheath in the central nervous system. This attack leads to patchy damage on the myelin sheath, resulting in asymmetrical neurological symptoms. Choices B, C, and D are incorrect because they do not accurately describe the pathophysiology of multiple sclerosis. In multiple sclerosis, it is the autoreactive lymphocytes that target and damage the myelin sheath, not acetylcholine receptors, T lymphocytes, or cortical motor cells.

Correct Answer: B

Rationale: Multiple dark bands on the nails can be a concerning sign of malignant melanoma, a type of skin cancer that can affect the nails. While some nail changes are considered normal variants, dark bands should not be dismissed lightly as they can indicate a serious condition like melanoma. Nail fungus typically presents differently, causing discoloration, thickening, or distortion of the nail without distinct dark bands. Additionally, aging can lead to various nail changes, but dark bands alone are not a common feature of normal aging.

Correct Answer: D

Rationale: The correct answer is D, Colon cancer. Colon cancer commonly presents with blood in the stool due to bleeding from the tumor. Gastroesophageal reflux (Choice A) is associated with heartburn and regurgitation of stomach contents into the esophagus. Crohn's disease (Choice B) is a type of inflammatory bowel disease that can cause symptoms like abdominal pain, diarrhea, and weight loss, but it does not typically present with blood in the stool as a primary symptom. Irritable bowel syndrome (Choice C) is a functional gastrointestinal disorder characterized by symptoms such as abdominal pain, bloating, and changes in bowel habits, but it does not usually involve blood in the stool as a prominent feature.

Correct Answer: C

Rationale: The correct answer is dementia with Lewy bodies (DLB). Hallucinations, parkinsonian symptoms (like bradykinesia and limb rigidity), and fluctuating cognition are characteristic of DLB. Alzheimer's disease (Choice A) typically presents with memory loss as a prominent feature. Vascular dementia (Choice B) is associated with a history of strokes and step-wise cognitive decline. Frontotemporal dementia (Choice D) often presents with changes in behavior and personality rather than the parkinsonian symptoms seen in this case.

Correct Answer: A

Rationale: The correct answer is A: live and can cause infection. In patients like the one described with a history of heart transplant and receiving long-term steroids, who are immunocompromised, live attenuated vaccines are contraindicated. Live vaccines contain weakened (attenuated) forms of the virus or bacteria, which can replicate and cause mild infections in healthy individuals but can lead to serious infections in immunocompromised individuals. Choices B, C, and D are incorrect because attenuated vaccines are not mutated, not inactive, and not pathogenic in healthy individuals, respectively.

Correct Answer: C

Rationale: The clinical findings of thin hair, exophthalmos, hyperreflexia, and pretibial edema are classic features of Graves disease, an autoimmune disorder that results in hyperthyroidism. Exophthalmos (bulging eyes) and pretibial edema (swelling in the lower legs) are particularly associated with Graves disease due to the autoimmune stimulation of the thyroid gland, leading to increased thyroid hormone production. Subacute thyroiditis (Choice A) typically presents with neck pain and tenderness, while autoimmune thyroiditis (Choice B) is commonly known as Hashimoto's thyroiditis, which presents with hypothyroidism symptoms. Hashimoto's disease (Choice D) is characterized by goiter and hypothyroidism, which contrasts with the hyperthyroidism seen in this patient.

Correct Answer: A

Rationale: The correct answer is Vitamin B12. Vitamin B12 deficiency can lead to megaloblastic anemia and neurological symptoms, including lower extremity paresthesias. Folate deficiency can also cause megaloblastic anemia but typically does not present with neurological symptoms. Iron deficiency leads to microcytic anemia, not megaloblastic anemia. Vitamin K deficiency is associated with coagulation abnormalities, not megaloblastic anemia.

Correct Answer: B

Rationale: In peripheral artery disease, pain in the lower extremities worsens with the elevation of the extremity because it diverts blood flow away from the affected area, exacerbating the pain. Choices A, C, and D are incorrect. Resting doesn't increase blood flow, a dependent position doesn't lead to blood pooling in this context, and pain worsening due to touch or massage is not a typical feature of peripheral artery disease.

Correct Answer: B

Rationale: The correct answer is B because sudden onset of behavioral changes is a typical symptom of delirium. Delirium is characterized by an acute and fluctuating disturbance in attention, awareness, and cognition. Choice A is incorrect because delirium is not a normal part of aging. Choice C describes memory issues, which can be seen in delirium but are less specific than sudden behavioral changes. Choice D, while it mentions the patient's independence, does not directly support the diagnosis of delirium.