ANSWER 16
The clinical picture is one of acute monoarthritis. The patient has a history of some hip
pains but this and the Heberden’s nodes are common findings in an 80-year-old woman,
related to osteoarthritis. The blood results show a raised white cell count and ESR, a raised
blood sugar, and renal function at the upper limit of normal.
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The differential diagnosis includes trauma, septic arthritis, gout and pseudogout.Differential diagnoses of pain in the kneeThe recent introduction of a thiazide diuretic for treatment of the hypertension increases
the suspicion of gout. Pseudogout is caused by deposition of calcium pyrophosphate crys-
tals and would be expected to show calcification in the articular cartilage in the knee
joint. The X-rays here show some joint space narrowing but no calcification in the articu-
lar cartilage. The fever, high white cell count and ESR are compatible with acute gout. The
raised glucose may also be a side-effect of thiazide diuretics. If this remains after the acute
arthritis has subsided then it may need further treatment. Precipitation of gout by thi-
azides is more likely in older women, particularly in the presence of renal impairment and
diabetes. It may involve the hands, be polyarticular and can affect existing Heberden’s
nodes.
The serum uric acid level is likely to be raised, but this occurs commonly without evidence
of acute gout. The definitive investigation is aspiration of the joint. The fluid should be
sent for culture and inspection for crystals. A high white cell count would be expected in
an acute inflammatory arthritis. The diagnosis is made from the needle-like crystals of
uric acid which are negatively birefringent under polarized light, unlike the positively
birefringent crystals of calcium pyrophosphate.
In this case the pain in the joint was partly relieved by the aspiration. Treatment with a
non-steroidal anti-inflammatory drug should be covered by a proton pump inhibitor in
view of her history of heartburn and indigestion. The thiazide diuretic was changed to an
angiotensin-converting enzyme inhibitor as treatment for her hypertension, and the blood
glucose settled.
- A careful drug history is an essential part of the history.
- Thiazide diuretics can precipitate diabetes and gout, especially in the elderly.