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 past medical history of primary biliary cirrhosis presents to the physician's office with complaints of increased pain in both wrists over the past two months. She usually experiences morning stiffness and pain in her wrists for at least 1 hour, but her symptoms gradually improve as she walks around her house during the day. She reports that her pain is also temporarily relieved by ibuprofen. The patient is otherwise healthy and receives daily ursodeoxycholic acid. Her blood pressure is 118/72 mmHg, her heart rate is 68/min, and her temperature is 36.5 °C (97.7 °F). Physical examination is remarkable for tenderness on deep palpation of the right trochanter. Radiographs reveal erosions of her metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. Which of the following findings is mostly associated with this patient's condition?]]
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::Primary biliary cirrhosis (PBC) is an autoimmune cholestatic liver disease characterized by the presence of anti-mitochondrial antibodies (AMA) that result in the inflammatory destruction of the intrahepatic bile ducts, fibrosis, and cirrhosis. PBC commonly affects middle-aged women. Diagnosis is often made when 2 out of the following 3 criteria are met: Biochemical evidence of cholestasis (elevated ALP or GGT), presence of disease-specific AMA, or histological feature of PBC. In addition, elevations in IgM levels are often observed in patients and may be helpful for the diagnosis. Patients with PBC (or other autoimmune diseases) are at increased risk of developing other autoimmune diseases. The incidence of rheumatoid arthritis (RA) has been observed to be increased among patients with PBC, and vice versa. Although the pathophysiology for the association is still unclear, studies have suggested several genetic and epigenetic mechanisms for the association of the 2 diseases. Susceptibility loci that involve both HLA and non-HLA regions have been identified and implicated in the pathogenesis of the association between PBC and RA. Development of other autoimmune diseases has also been associated with PBC, including Sjogren's syndrome, systemic sclerosis, and autoimmune thyroiditis. The patient in the vignette presences with symptoms and signs consistent with RA, including morning stiffness and pain that are relieved by movement during the day, erosions of the MCP and PIP joints. 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
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