WBR0280

Author	[[PageAuthor::Ayokunle Olubaniyi, M.B,B.S [1] (Edited by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Musculoskeletal/Rheumatology
Prompt	[[Prompt::A 60 year-old woman with a medical history of primary biliary cirrhosis (PBC) comes to your office due to increased pain in her right hip and thigh over the past two weeks. The pain is exacerbated when she lies on her right side while sleeping, and is temporarily relieved with ibuprofen. She usually experiences stiffness and pain in her hip the morning following sleeping in this position that gradually lessens as she walks around her house and does chores. The patient is otherwise healthy and takes ursodeoxycholic acid (UDCA). She is 156 cm tall and weighs 89 kg. Upon examination, vital signs appear to be normal. The patient demonstates tenderness on deep palpation of the right trochanter. Radiographs also reveal erosions of her metacarpophalangeal (MCP) and proximal interphalangeal joints (PIP). Which of the following test results is the most relavent to the diagnosis of this patient?]]
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 the X-ray.
Answer C Explanation	[[AnswerCExp::A “pencil-in-cup” deformity on X-ray is observed in patients with 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 the X-ray.
Answer D Explanation	[[AnswerDExp::Presence of subchondral cysts and osteophytes on an X-ray is seen in cases of osteoarthritis. Classic presentation involves pain in the weight bearing joints such as the hip joint and the knee joint. Involvement of the proximal interphalangeal joints (Bouchard's nodes) and the distal interphalangeal joints (Heberden's nodes) is pathognomonic. It usually does not impact the MCP joint.]]
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 observed in cases of 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, which can lead to liver cirrhosis. PBC can be associated with other autoimmune disorders such as Sjögren's syndrome or autoimmune thyroid disease, but its association with rheumatoid arthritis is very rare and poses a difficulty in the management of the disorder. Rheumatoid arthritis usually affects the small synovial joints – MCP and PIP, but not the distal interphalangeal joints (DIP). In this patient, the joint pain is worse in the morning and gradually lessens as the day progresses, while the pain in osteoarthritis reduces with rest and worsens with prolonged use. Educational Objective: The presence of an autoimmune disorder in a patient warrants searching for other autoimmune disorders. Rheumatoid arthritis must be differentiated from osteoarthritis. RA mainly affects the MCP and PIP, sparing the DIP. References: First Aid 2014 366]]
Approved	Approved::Yes
Keyword	WBRKeyword::Autoimmune disorders, WBRKeyword::Arthritis, WBRKeyword::Primary biliary cirrhosis, WBRKeyword::Rheumatoid arthritis
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::