Gout

Deposition of sodium urate monohydrate crystals in synovial membranes, articular cartilage, ligaments, bursae leading to destruction of cartilage

·        Age of onset is usually greater than 40 years; males much more often than females

·  Causes:

o       Idiopathic Gout

§         M:F = 20:1

§         Overproduction of uric acid

§         Abnormality of renal urate excretion

o       Secondary Gout

§         Rarely cause for radiographically apparent disease

§         Myeloproliferative disorders, e.g. polycythemia vera, leukemia, lymphoma, multiple myeloma

§         Blood dyscrasias

§         Myxedema, hyperparathyroidism

§         Chronic renal failure

§         Glycogen storage disease

§         Myocardial infarction

§         Lead poisoning

·  Stages:

o       Asymptomatic hyperuricemia

o       Acute monarticular gout

o       Polyarticular gout

o       Chronic tophaceous gout = multiple large urate deposits

·  Location:

o       Joints: hands + feet (1st MTP joint most commonly affected = podagra), elbow, wrist

§         Carpometacarpal compartment especially common), knee, shoulder, hip, sacroiliac joint (15%, unilateral)

o       Ear pinna > bones, tendon, bursa

·        Radiologic features usually not seen until 6-12 years after initial attack

·        Radiologic features present in 50% of inflicted patients

·  Soft tissue findings

o      Calcific deposits in gouty tophi in 50% (only calcium urate crystals are opaque)

o      Eccentric juxta-articular lobulated soft-tissue masses (hand, foot, ankle, elbow, knee)

o       Bilateral olecranon bursitis

o       Aural calcification

·  Joint findings

o       Preservation of joint space initially

o       Absence of periarticular demineralization

o       Erosion of joint margins with sclerosis

o       Cartilage destruction late in course of disease

o       Periarticular swelling (in acute monarticular gout)

o       Chondrocalcinosis (menisci, articular cartilage of knee) resulting in secondary osteoarthritis

Gout. The great toe demonstrates extensive juxta-articular erosions
with soft tissue swelling and little osteoporosis

·  Bone findings

o       "Punched-out" lytic bone lesion ± sclerosis of margin

o       "Mouse / rat bite" from erosion of long-standing soft-tissue tophus
o       "Overhanging margin" (40%)

Gout. There are characteristic erosions with "overhanging" edges seen in gout (white arrows).
These have been characterized as appearing like "rat-bites."

o       Ischemic necrosis of femoral / humeral heads

o       Bone infarction

·  Coexisting disorders:

o       Psoriasis

o       Glycogen storage disease Type I

o       Hypo- and hyperparathyroidism

o       Down’s syndrome

o       Lesch-Nyhan syndrome (choreoathetosis, spasticity, mental retardation, self-mutilation of lips + fingertips)

·        Treatment: colchicine, allopurinol (effective treatment usually does not change x-ray findings)