WBR0280

Author	[[PageAuthor::Ayokunle Olubaniyi, M.B,B.S [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Musculoskeletal/Rheumatology
Prompt	[[Prompt::A 60 year-old woman with a past medical history of primary biliary cirrhosis (PBC) comes to your office because of a 2 week history of increasing pain of the right hip and thigh. The pain is exacerbated by lying on her right side while sleeping, and temporarily relieved with ibuprofen. She usually has stiffness and pain in the hip during the following morning that gradually diminishes as she walks around her house and does house chores. The patient is otherwise healthy and takes ursodeoxycholic acid (UDCA). She is 156 cm tall and weighs 89 kg. Vital signs are normal. Physical examination discloses tenderness on deep palpation of the right trochanter. Radiographs also revealed erosions of her metacarpophalangeal (MCP) and proximal interphalangeal joints (PIP). Which of the following is needed in order to make a diagnosis? A) Needle-shaped, negatively birefringent crystals within the joint space B) Positive antibody against the Fc portion of IgG C) “Pencil-in-cup” deformity on X-ray D) Presence of subchondral cysts and osteophytes on X-ray E) Rhomboid-shaped, positively birefringent crystals within the joint space.]]
Answer A	AnswerA::Needle-shaped, negatively birefringent crystals within the joint space.
Answer A Explanation	[[AnswerAExp::Needle-shaped, negatively birefringent crystals within the joint space are observed in patients with gout. This is more common in males, and it results from precipitation of monosodium urate crystals into the joints due to hyperuricemia.]]
Answer B	AnswerB::Positive antibody against the Fc portion of IgG.
Answer B Explanation	AnswerBExp::Positive antibody against the Fc portion of IgG refers to a positive rheumatoid factor which is present in about 80% of patients. This is an autoimmune disorder affecting the synovial joints.
Answer C	AnswerC::“Pencil-in-cup” deformity on X-ray.
Answer C Explanation	[[AnswerCExp::“Pencil-in-cup” deformity on X-ray refers to psoriatic arthritis. This is a seronegative spondyloarthropathy (arthritis without rheumatoid factor) common in patients with the chronic skin condition called psoriasis.]]
Answer D	AnswerD::Presence of subchondral cysts and osteophytes on X-ray.
Answer D Explanation	[[AnswerDExp::Presence of subchondral cysts and osteophytes on X-ray is seen in osteoarthritis. Classic presentation involves pain in the weight bearing joints such as the hip and knee joints. Affectation of the proximal interphalangeal joints (Bouchard’s nodes) and the distal interphalangeal joints (Heberden’s nodes) is pathognomonic. It usually spares the MCP.]]
Answer E	AnswerE::Rhomboid-shaped, positively birefringent crystals within the joint space.
Answer E Explanation	[[AnswerEExp::Rhomboid-shaped, positively birefringent crystals within the joint space are seen in pseudogout.]]
Right Answer	RightAnswer::B
Explanation	[[Explanation::This patient has a past medical history of Primary Biliary Cirrhosis (PBC) which is an autoimmune disorder characterized by chronic destruction of bile ducts that can lead to liver cirrhosis. PBC can be associated with other autoimmune disorders such as Sjögren’s syndrome, autoimmune thyroid disease, but its association with rheumatoid arthritis is very rare and poses a difficulty in its management. Rheumatoid arthritis usually affects the small synovial joints – MCP and PIP, but spares the distal interphalangeal joints (DIP). The joint pain is worse in the morning but gradually lessens as the day progresses while the pain in osteoarthritis reduces with rest and worsens with prolonged use. Educational Objective: References: ]]
Approved	Approved::Yes
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