What is a cause of the crystallization within the synovial fluid of the joint affected by gouty arthritis?

Correct Answer: B

Rationale: The correct answer is B: Underexcretion of uric acid. Gouty arthritis is primarily caused by the underexcretion of uric acid, leading to its accumulation in joints and subsequent crystallization. Choices A, C, and D are incorrect as they do not directly relate to the pathophysiology of gout. Destruction of proteoglycans, overexcretion of uric acid, and increased absorption of uric acid are not primary causes of gouty arthritis.

Correct Answer: C

Rationale: Dark urine is a classic symptom of rhabdomyolysis. When muscle breakdown occurs, myoglobin is released into the bloodstream and filtered by the kidneys, leading to dark urine. Paresthesias (choice A) refer to abnormal sensations like tingling or numbness and are not typically associated with rhabdomyolysis. Bone pain (choice B) is not a prominent symptom of rhabdomyolysis. Diarrhea (choice D) is not a common complaint in rhabdomyolysis cases and is not directly related to muscle breakdown.

Correct Answer: B

Rationale: Bullous impetigo is the correct answer because it is caused by a Staphylococcus aureus toxin that leads to exfoliation and the formation of large blisters. Herpes simplex I virus (Choice A) causes cold sores and is not associated with exfoliation and blister formation. Necrotizing fasciitis (Choice C) is a severe skin infection involving the deeper layers of skin and subcutaneous tissues, typically caused by bacteria such as Streptococcus or Clostridium species, not Staphylococcus aureus. Cellulitis (Choice D) is a common bacterial skin infection, but it does not involve exfoliation and blister formation as seen in bullous impetigo.

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. Hemangiomas, congenital dermal melanocytosis (i.e., Mongolian spots), and macular stains are birthmarks that usually fade or regress as the child gets older. Hemangiomas are vascular birthmarks that often shrink and fade over time. Congenital dermal melanocytosis (Mongolian spots) are blue-gray birthmarks commonly found on the lower back and buttocks of infants, which typically fade by adolescence. Macular stains, also known as salmon patches, are pink or red birthmarks that usually fade within the first few years of life. Choice D is correct because all the mentioned birthmarks tend to diminish as the child grows, unlike choices A, B, and C which do not fade or regress with age.