Approximately what percentage of patients with psoriasis develop an associated arthropathy?
Correct Answer E:
Psoriatic arthropathy:
Psoriatic arthropathy correlates poorly with cutaneous psoriasis and often precedes the development of skin lesions. Around 10% percent of patients with skin lesions develop an arthropathy with males and females being equally affected.
Types*:
Management:
*Until recently it was thought asymmetrical oligoarthritis was the most common type, based on data from the original 1973 Moll and Wright paper. Please see the link for a comparison of more recent studies.
You review a 48-year-old woman who is taking methotrexate for rheumatoid arthritis.
Concurrent prescription of which other medication should be avoided?
Correct Answer B: There is an increased risk of haematological toxicity when trimethoprim is prescribed alongside methotrexate.
Methotrexate:
Methotrexate is an antimetabolite which inhibits dihydrofolate reductase, an enzyme essential for the synthesis of purines and pyrimidines.
Indications:
Adverse effects:
Pregnancy:
Prescribing methotrexate:
A 68-year-old presents with a painful swollen left knee which has failed to settle after a weeks rest. There is no history of trauma. On examination he has a moderate sized effusion. A plain radiograph is reported as follows:
What is the most likely diagnosis?
Correct Answer A: This x-ray describes chondrocalcinosis. Non-specific changes such as loss of joint space are common in this age group and pseudogout itself may cause osteoarthritic-like changes.
Pseudogout:
Pseudogout is a form of microcrystal synovitis caused by the deposition of calcium pyrophosphate dihydrate in the synovium.
Risk factors:
Features:
A 69-year-old man presents with an acute episode of gout on his left first metatarsal-phalangeal joint.
What is the most likely underlying mechanism?
Correct Answer B: The vast majority of gout is due to decreased renal excretion of uric acid.
Decreased renal excretion of uric acid is thought to account for 90% of cases of primary gout. Secondary risk factors such as alcohol intake and medications should also be investigated.
Gout: predisposing factors:
Gout is a form of microcrystal synovitis caused by the deposition of monosodium urate monohydrate in the synovium. It is caused by chronic hyperuricaemia (uric acid > 0.45 mmol/l).
Decreased excretion of uric acid:
Increased production of uric acid:
Lesch-Nyhan syndrome:
*Aspirin in a dose of 75-150mg is not thought to have a significant effect on plasma urate levels - the British Society for Rheumatology recommend it should be continued if required for cardiovascular prophylaxis.
A 50-year-old man with no past medical history is investigated for ongoing back pain. He is found to have a vertebral collapse secondary to osteoporosis.
What is the most appropriate test to determine the cause of his osteoporosis?
Correct Answer E: Osteoporosis in a man - check testosterone.
Whilst thyrotoxicosis is a known cause of osteoporosis, testosterone deficiency is much more likely in a middle aged male.
Osteoporosis: causes: Risk factors:
Diseases which predispose:
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