A 57-year-old woman presents to her family doctor with complaints of progressive unilateral foot swelling, without history of recent trauma or pain. She first noticed the problem months ago, but more recently is finding it difficult to get her foot into her shoes, and she has trouble walking. Her past medical history includes long-standing mild hypertension, mild obesity, insulin-dependent diabetes mellitus and mild hypercholesterolemia.
The most likely diagnosis is:
a) Charcot foot
c) hypertrophic osteoarthritis
e) subacute stress fracture
The most correct answer is (a): Charcot foot
Charcot foot is the term given to describe the progressive neuropathic degeneration of the mid-foot joints and associated osseous structures. The term Charcot joint could be used to describe any neuropathic joint that results in bony destruction, bone resorption and deformity and is usually associated with soft tissue swelling. The abnormality frequently takes months or years to develop and generally does so without pain (due to its neuropathic nature — loss of local pain sensation). The condition can eventually lead to skin ulceration (from weight-bearing on the deformed body part) and possible infection, which would then typically include symptoms of fever, marked local erythema and more proximal extremity pain. If left untreated, the disease process may lead to a need for amputation.
The most common cause of a Charcot joint is neuropathy relating to insulin-dependent diabetes mellitus, as this lady has, with chronic poor blood glucose control. Less common causes include alcoholic neuropathy, certain CNS disorders (spinal cord injury, syringomelia, myelomeningocele, cerebral palsy), as well as uncommon conditions such as 3rd-stage syphilis (termed ‘tabes dorsalis’) and leprosy.
If discovered relatively early, disease progression can be slowed or halted with use of casting and perhaps walking braces. Surgical correction is generally not very helpful. The most important differentiation after initial discovery is to rule out associated infection (osteomyelitis). Bone and gallium scans might be helpful, along with MRI, in this differentiation. A skin ulcer may be present in uninfected Charcot foot, but if an ulcer isn't present, the chance of associated infection is much lower.
Hypertrophic osteoarthritis may result in large bulky marginal osteophytes, but without the destruction and collapse. Gout in the foot generally affects the 1st MTP joint and doesn’t ordinarily result in this degree of bone destruction and deformity. Stress fractures in the foot more commonly involve the metatarsal shafts, or the calcaneus, and typically present with progressive pain.
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