Tropical Medicine Mission Index of Diseases About Tropical Medicine Tropical Medicine Home Page Tropical Medicine Staff

Next Page

Differential Diagnosis

There are very few bone infections which are bilateral, frequently symmetrical, and which affect epiphyses primarily. There are equally few in which the patient remains so clinically unaffected, in which sequestration does not follow severe bone involvement, and in which surgery and antibiotic therapy have no effect. (Both are probably contraindicated!) For this reason, recognition of the disease is important to spare the unfortunate sufferer from unnecessary treatment.

Smallpox may never again be seen in the acute stage, but its end results may be seen for another decade or two, especially in the tropics. Short and stubby metacarpals or phalanges, unusual deformities of long bones, flaring of the metaphyses, flail joints, or ankylosis with precocious osteoarthritis may all be indications of the etiology. Most important, such abnormalities will be strongly suggestive of prior smallpox osteomyelitis if they are bilaterally symmetrical in the limbs (although not necessarily in degree of involvement) and show no evidence of sequestration or spiculated new bone. The radiographic appearance may be complicated by a pyogenic infection, and then the multiplicity of the lesions may be an important factor in recognizing the underlying disease.

There is much similarity between osteomyelitis variolosa and infantile cortical hyperostosis (Caffey's disease) which supports the speculation that Caffey's disease may also be a viral infection. Both diseases erupted in epidemics but are, fortunately, rarely seen today. The clinical presentation of Caffey's disease is similar except that there is no rash. The patients may have raised or normal temperatures. There is very little bone pain in most children with Caffey's disease, and none have the acute pain which is so typical of acute pyogenic osteomyelitis. The radiological changes are similar to those of smallpox, both in their development and in their symmetry. Caffey's disease often affects the mandible, clavicle, ribs, scapula, and other bones which are only rarely affected by smallpox, but affected bones may have the same appearance of pseudosequestration and take the same 2 years or more to heal. Fortunately, Caffey's disease does not cause bony ankylosis as occurs with smallpox, a more destructive entity.

The differential diagnosis of healed smallpox osteitis includes old septic or tuberculous arthritis and previous yaws or luetic (treponemal) osteomyelitis. The end stages of smallpox osteitis may occasionally bear a superficial resemblance to achondroplasia, but only a few bones will be involved in smallpox and there will often be inequality in their lengths. Moreover, although the bones in osteomyelitis variolosa may be short and have flaring of the metaphyses, they are not as massive as the bones of achondroplasia. The differential diagnosis of short digits resulting from smallpox is aided by the almost inevitable presence of bone or joint disease elsewhere in the skeleton.

Back to the Table of Contents

Copyright: Palmer and Reeder