Correct Answer: A

Rationale: Abrupt withdrawal or discontinuation of prednisone, a corticosteroid, can lead to adrenal crisis. This occurs due to the suppression of the adrenal glands' natural cortisol production caused by prolonged exogenous steroid administration. Adrenal crisis presents with symptoms such as weakness, fatigue, abdominal pain, and hypotension. Hypercortisolism (Cushing syndrome) results from chronic excessive exposure to cortisol, not abrupt withdrawal. ACTH stimulation would be expected in response to low cortisol levels, not as a direct consequence of prednisone withdrawal. Thyroid crisis (thyroid storm) is associated with severe hyperthyroidism and is not directly related to corticosteroid withdrawal.

Correct Answer: A

Rationale: Psoriasis is the correct answer because it is a chronic inflammatory skin condition characterized by features such as angiogenesis (formation of new blood vessels), immune cell activation (especially T cells), and excessive keratinocyte proliferation. This results in the typical symptoms seen in psoriasis, such as red, scaly patches on the skin. Melanoma is a type of skin cancer arising from melanocytes, not characterized by the features mentioned. Atopic dermatitis is a different skin condition involving eczematous changes, not specifically associated with the described characteristics of psoriasis. Urticaria is a skin condition characterized by hives and does not involve the same pathophysiological processes as psoriasis.

Correct Answer: B

Rationale: Most body fluids are located within cells in the intracellular space. While the extracellular space also contains body fluids, the majority is found within the cells. Intravascular space refers to fluids within blood vessels, and transcellular space includes fluids in compartments like cerebrospinal, pleural, and peritoneal cavities.

Correct Answer: C

Rationale: Multiple sclerosis is characterized by the immune system mistakenly attacking the myelin sheath in the central nervous system. This results in the formation of lesions that can occur in different parts of the central nervous system, leading to varied symptoms depending on the location of the damage. Choice A is the correct answer because it accurately describes the pathophysiology of multiple sclerosis. Choices B, C, and D are incorrect because they describe mechanisms or locations that are not associated with the pathogenesis of multiple sclerosis.

Correct Answer: C

Rationale: Benign positional vertigo is typically triggered by changes in head position, such as bending forward or turning over in bed. This change in position leads to brief episodes of vertigo, often associated with nystagmus, which is rapid, involuntary eye movements. Pupillary changes and headaches are not typical features of benign positional vertigo, making choices B and A incorrect. Nystagmus in benign positional vertigo usually stops when the eyes fixate on an object, so choice D is also incorrect.