WBR0280

Author	[[PageAuthor::Ayokunle Olubaniyi, M.B,B.S [1] (Reviewed by Yazan Daaboul, M.D. and Alison Leibowitz [2])]]
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 moves her wrists during the day. She reports that her pain is also temporarily relieved by ibuprofen. The patient receives daily ursodeoxycholic acid and reports no known drug or food allergies. 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 ulnar deviation in fingers of both upper extremities and boutonniere deformities of the PIP joints. A tender subcutaneous nodule is palpated over the left olecranon. Radiographs reveal erosions of her metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints with sparing of the distal interphalangeal (DIP) 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. Gout is common among males; it is associated with hyperuricemia and results from precipitation of monosodium urate (MSU) crystals into the joints.]]
Answer B	AnswerB::Positive antibodies against the Fc portion of IgG
Answer B Explanation	[[AnswerBExp::Positive antibodies against the Fc portion of IgG refers to a positive rheumatoid factor (RF). RF is a sensitive but non-specific biomarker that is present in approximately 80% of patients. It is also present in several other autoimmune and connective tissue diseases.]]
Answer C	AnswerC::“Pencil-in-cup” deformity on x-ray
Answer C Explanation	[[AnswerCExp::A “pencil-in-cup” deformity on x-ray is observed in patients with psoriatic arthritis, which is a seronegative spondyloarthropathy (presence of inflammatory arthritis with no rheumatoid factor) that may be present in patients with 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 observed in patients with 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 characteristic.]]
Answer E	AnswerE::Rhomboid-shaped, weakly positively birefringent crystals within the joint space
Answer E Explanation	[[AnswerEExp::Rhomboid-shaped, weakly positively birefringent basophilic crystals within the joint space are characteristic of pseudogout. Pseudogout is a form of arthritis caused by the deposition of calcium pyrophosphate crystals within the joint space. It often involves the knee joint among patients older than 60 years.]]
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). It results 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 in 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. Most importantly, the patient in the vignette presences with symptoms and signs consistent with RA, such as symmetric morning stiffness and pain of the joints that persist for more than 1 hour and are relieved by movement during the day. Physical examination findings, namely ulnar deviation, boutonniere deformities of the PIP joints, and tender subcutaneous nodules present over the olecranon or the extensor surface of the forearms are characteristic features of RA. Finally, radiographic findings of this patient's joint that demonstrate erosions of the MCP and the PIP joints with sparing of the DIP are classic of RA. Pannus formation of the MCP and PIP joints and Baker cyst, which is a true cyst that is usually present in the popliteal fossa, are also classically observed in RA. Approximately 80% of patients with RA have positive rheumatoid factor (RF), which is an autoantibody against the Fc portion of IgG. RF is a sensitive but non-specific biomarker, given its presence in a number of inflammatory and connective tissue diseases. Clinically, anti-cyclic citrullinated peptide (CCP) antibody is a more specific biomarker that is often used to confirm the diagnosis of RA. Educational Objective: Patients diagnosed with autoimmune diseases are at increased risk of developing other autoimmune diseases. Rheumatoid arthritis (RA) is an autoimmune inflammatory arthritis that is characterized by the presence of symmetric joint pains that typically last more than hour and are relieved by movement. Physical examination findings consistent with RA include ulnar deviation of the fingers, pannus formation, Baker's cyst in the popliteal fossa, and tender subcutaneous nodules over the olecranon or the extensor surfaces of the forearm. The majority of patients with RA have a positive rheumatoid factor (RF), which is an autoantibody against the Fc portion of IgG. References: McInnes IA, Schett G. The pathogenesis of rheumatoid arthritis. N Engl J Med. 2011;365:2205-2219. Siegel JL, Luthra H, Donlinger J, et al. Association of primary biliary cirrhosis and rheumatoid arthritis. J Clin Rheumatol. 2003;9(6):340-3. First Aid 2014 366]]
Approved	Approved::Yes
Keyword	WBRKeyword::Autoimmune disorder, WBRKeyword::Arthritis, WBRKeyword::Primary biliary cirrhosis, WBRKeyword::Rheumatoid arthritis, WBRKeyword::Rheumatoid factor, WBRKeyword::Biomarker
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