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

Next Page

Clinical Characteristics

Smallpox is a remarkably variable disease. It may be a relatively benign infection (variola minor or alastrim), healing without scarring, or a disease that is severe and rapidly fatal. In general, the African and Asian variola major is a more severe and fulminating illness, whereas the variola minor of South America is more benign, but both vary considerably in individual patients. All infections start with fever, headaches, backache, tiredness, and an erythematous rash over the face and chest. This redness becomes more papular, then vesicular and umbilicated. The vesicles fill with a milky fluid, which resembles pus; because secondary infection often occurs, they may become truly pustular. As the vesicles dry, they become crusty. The resulting scarring may be negligible or severe. It tends to be most noticeable on the face and is made worse by the secondary bacterial infection (Fig. 40.2). Death can occur even before the rash has developed. Some patients develop a severe hemorrhagic rash, with widespread bleeding beneath the vesicle. The smallpox vesicles may spread and become confluent, stripping large areas of epidermis. Such broadly denuded areas are fertile ground for secondary infection and predispose to septicemia. Similar lesions occur in the mucous membranes of the mouth, palate, larynx, and trachea.



Fig. 40.2 A-D. The clinical spectrum of smallpox. (A) The acute disease in a West African child. (B) The rash is fading; the acute stage is over in a young child from Malawi. (C) The rash is almost gone but both elbows and the wrists are swollen. Also a child from Malawi. (D) No visible rash; there are a few scars on the legs. Swelling of both elbows, both knees and ankles. Visible thickening of the tibiae. The child is well clinically but has severe osteomyelitis variolosa. (B-D courtesy of Dr. J.C. Davidson and Dr. P.E.S. Palmer: Jounal of Bone and Joint Surgery, 1963).


There is no relationship between the severity of the smallpox infection and the occurrence or the extent of bone and joint involvement. The smallpox may be so clinically mild that it may be overlooked entirely, and yet the osteomyelitis may be severe. The diagnosis in several patients has been recognized by their radiological findings and only subsequently confirmed clinically as smallpox. There is often great disparity between the serious bone and joint abnormalities and the clinical condition of the patient. This is typical of the disease and is an important diagnostic feature. On the other hand, children (the bone infection never occurs in adults) may have a very severe clinical smallpox infection, and a careful radiological search may fail to reveal any evidence of bone infection.

The majority of patients with osteomyelitis are less than 10 years old, but it has been recorded as late as 16 years. There is no correlation with the patient's nutrition or general condition before the smallpox infection, nor is there any association with sickle cell disease or other abnormality, congenital or acquired.

Clinical bone infection may be recognized 5 days after the onset of the rash and while the skin changes are still obvious; in other patients it may be delayed as long as 28 days after the diagnostic skin changes are first seen and when the patient has only minor residual scarring or discoloration. In, some patients, the severity of the general disease prevents early recognition of the bone and joint infections; in many with less severe infection, the joint and bone problems become apparent as the patient becomes ambulatory. The patient's first complaint is usually of swelling around a joint, but a careful radiological search will show thickening of a bone, such as the ulna, humerus, or fibula, before the patient is aware of it. Bone pain is not a major symptom, unlike other types of osteomyelitis; movement of a joint may be restricted and some patients may complain of discomfort. Occasionally this restriction is noticed before the swelling of the soft tissues around the joint is visible. There is often an effusion into the joint, but it may be difficult to recognize because of the overlying soft tissue swelling. The elbows are most often affected and the changes are frequently bilateral. In the majority of young patients with skeletal involvement, this clinically benign condition produces much more deformity than the symptoms would suggest.

In severely affected patients, the joint may become totally disorganized and pathological fracture can occur. Clinically this presents as abnormal mobility. In some series, the elbows show this most frequently, in others the ankles are the most often affected. Sinuses from severely affected joints may appear spontaneously, and this seems to be more frequent when the effusion has not been aspirated, or has been aspirated too late. Simple aspiration of the fluid, relieving the tension within the joint, may prevent development of sinuses but carries the contrary risk of introducing bacterial infection.

The clinical appearance of these children is such that it is often difficult to believe that they are not running a considerable fever. A child with grossly swollen elbows and ankles may seem otherwise well. Usually one-third of the patients are afebrile, one-third have a low fever, and the remaining third will have a swinging temperature. However, careful the physical examination, infection of bone may not be recognized unless sought radiologically.

The clinical progress of the osteitis is slow and, again, unrelated to that of the smallpox. Improvement may occur in 1 or 2 months, and mildly affected patients may return to normal within 4 months. Others take up to 2 years and, although clinically well, may be left with radiological abnormalities. Fusion of a joint may be a late result. The unfortunate tribal doctor in some parts of Africa has been blamed by missionaries when children have bilaterally fused elbows; this is unfair because his, or her, treatment is unlikely to have much effect on a variola infection of a joint! Other children will be left with short and irregular digits and sometimes shortened long bones. Fusion is not the only sequel to joint involvement; the joints may remain flail, may subluxate and dislocate, or become fixed in a grossly deformed position. Arthritis may precede ankylosis. Antibiotics have no effect on the progress or prognosis.

Back to the Table of Contents

Copyright: Palmer and Reeder