Pyomyositis A article by Theriainteresting and Vaughn

Echeverin this issue of the Journal (page 856) raises once again the question of the appropriate nomenclature of "tropical diseases." In general, clinical entities that are described as occurring largely in the less-developed regions of the world (often, but by no means always, found in those areas with a tropical climate) can be grouped under one of four headings that account for their epidemiologic characteristics: 1. Diseases that have an overriding association with low standards of living, with consequent higher prevalence in populations suffering from poor nutrition, poor hygiene, and lowered resistance to disease because of multiple parasitic and infectious processes. Examples of this group, often very common in the West before the rise in living standards of the past century, include the diarrhea-pneumonia complex of early childhood (accounting for perhaps half of all childhood deaths occurring annually on the globe), infestation with intestinal parasites such as Ascaris lumbricoides, and widespread tuberculosis Attention should also be drawn to the syndromes of early childhood malnu¬ trition so prevalent in Africa, Asia, and Latin America. 2. Diseases in which geographic/ climatic factors play a predominant role. Examples here are vector-borne entities such as onchocerciasis and yellow fever. 3. Diseases in which genetic, eth¬ nic, or cultural differences are paramount, such as kuru, described only in New Guinea. 4. Diseases that express a combi¬ nation of more than one of the above factors. These combinations, especial¬ ly of groups 1 and 2, are very frequent, since the tropical regions have been, to date, heavily associated with pov¬ erty and malnutrition. The historical

"Tropical" Disease?

tendency

among Europeans and North Americans to loosely regard as tropical those regions falling outside their homelands (especially in associ¬ ation with the expansion of colonial¬ ism in the 18th and 19th centuries) often creates confusion that prevents accurate assessment of the possible tropical nature of a given condition. Further, the distinction between tropical and nontropical disease is progressively weakened in these days of rapid transport and growing inter¬ dependence of people in and from all regions of the globe.

Clinical Aspects

Pyomyositis, single

or multiple ab¬ of skeletal muscle, is described as a rare disease in temperate cli¬ mates; recent standard textbooks of pediatrics emphasize its infrequent oc¬ currence.1·2 Stress has been laid on the resistance of muscle tissue to bac¬ terial invasion.3 However, the clinical entity is well recognized, and the pre¬ ponderance of Staphylococcus aureus in primary muscle abscesses is similar in temperate and tropical areas. More space in American texts, is devoted to muscle and soft tissue necrosis with Clostridium infection, following pen¬ etrating wounds and local anaerobic conditions. In contrast, pyomyositis is recog¬ nized as a common condition in trop¬ ical areas, accounting for as much as 4% of all surgical admissions in one series from eastern Africa." Though it occurs in all racial and ethnic groups, the preponderance of cases has been described in the indigenous popula¬ tion in reports from Africa. Over 90% of the organisms isolated from the abscesses have been S aureus, and multiple abscesses are not uncommon, thus suggesting hematogenous seed¬ ing of the bacteria. The large muscles of the limbs and limb girdles are de¬ scribed as the most frequent sites of scesses

Predisposing trauma (viewed retrospectively) is frequent

occurrence.5

but not invariable. The course of the disease and its clinical presentation are most often subacute, with the absence of florid and classical signs and symptoms of abscess formation, sometimes lead¬ ing, as in the first case in the accom¬ panying article by Echeverría and

Vaughn to diagnostic pitfalls. Thus, the clinical aspects of pyo¬ myositis, in both tropical and temper¬ ate climates, are well described, at

least after the initiation of abscess formation. The abscesses are located beneath the deep fascia, and the fre¬ quency of multiple abscesses suggests hematogenous origin; the rarity of positive blood cultures at the time of diagnosis suggests a previous and un¬ recognized bacteremia.

Pathogenesis The uncertainties and arguments concerning the pathogenesis of pyo¬ myositis largely relate to the nature of local or systemic predisposing fac¬ tors that prepare the abscess site(s) for the invading Staphylococcus. Pre¬ vious local trauma, leading to muscle injury and local necrosis, would seem to be the most likely predisposing fac¬ tor in a majority of cases. Miyake was able to produce muscle abscess forma¬ tion at specific local sites in rabbits

by forceps-pinch trauma or prolonged electrical stimulation following intra¬ venous injection of staphylococci.6 Halsted, however, was unable to pro¬

duce muscle abscesses in the presence of similar inoculation by compromis¬ ing local blood supply.7 Other factors that might reason¬ ably be associated with local damage to muscle tissue have not been found in reliable statistical association with cases of pyomyositis. These include sickle cell disease and tissue para¬ sites (Trichinella, Wuchereria, On-

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Selected Findings in Six Patients With Pyomyositis

Diagnosed

in the United States

Authors & Cases Echeverría &

T~ Recent entry to US from tropical area (No. of months preceding

diagnosis) prior trauma to local (No. of weeks preceding diagnosis) Multiple abscesses Known

area

S aureus as causative organism Indications of tissue parasites

*

=

Total

Levin et al9

Vaughan 2

+(2)

Altrocch¡i°

(6 Cases)

+(1V2)

4-5

+(3) +(1)



+(5) -H2V2) +(1) + +

+

+ -T

-T*

t(V2) +

-

+

-

+

+F

+Ft +T/AÍ

2/6

is a secondary or joint invader in association with another bacterium or virus, an argument advanced on the basis of a geographic association of pyomyositis in African surveys with truly tropical, hot, humid zones.4·8 However, it bears mentioning that indolent, superficial infections are particularly prevalent in these situ¬ ations, especially where the rural ag¬ ricultural population is lightly clothed and barefoot; these local infections could serve as a source of transient, unrecognized bacteremia. In addition to the two cases de¬ scribed in this issue of the Journal, four other cases have recently ap¬ peared in the US literature.9·10 Se¬ lected features of these case reports are instructive (Table). Of the six patients, the three who had recently resided outside the United States in tropical areas had multiple abscesses; the other three patients who has resided entirely in the United States had single abscesses. Previous trauma at the abscess site(s) occurring one to

five weeks before diagnosis was noted in four patients and possibly in a fifth. All abscesses were caused by S Aureus. Two of the three patients with recent foreign residence had evidence of filarial infection (the prevalence of filarial infection in recent US immigrants from tropical areas is unknown). It seems reasonable to speculate that pyomyositis, which can clearly occur in a purely nontropical context, is a condition with two necessary pre¬ requisites. First, there must be pre¬ existing local damage (and necrosis?) of muscle tissue. This probably can occur from one of several factors, ex¬ ternal trauma being the most com¬ mon, but possibly also due to tis¬ sue parasites. Second, a transient and usually unrecognized bacteremia, caused most usually by S aureus, dis¬ seminates organisms to the prepared site(s). The combination of poor nu¬ trition and other factors leading to decreased host resistance to infection can well facilitate this process; these factors will be most commonly found in the impoverished tropical areas of the world. No reliable evidence indi-

1. Nelson WE, Vaughan VC, McKay RJ: Textbook of Pediatrics, ed 9. Philadelphia, WB Saunders Co, 1969, p 1318. 2. Barnett HC, Einhorn AH: Pediatrics, ed 15. New York, Appleton-Century-Crofts Inc, 1972, p 1032. 3. Adams RD, Denny-Brown D, Pearson CM: Diseases of Muscle: A Study in Pathology, ed 2. New York, Harper & Bros, 1962, p 386. 4. Horn CV, Master S: Pyomyositis tropicans

Uganda. East Afr Med J 45:463-471, 1968. 5. Traquair RN: Pyomyositis. J Trop Med Hyg 50:81-89, 1947. 6. Miyake H: Beitrage zur Kenntnis der sogenannten myositis Infectiosa. Mitt Grenzgeb Med Chir 13:155-198, 1904. 7. Halsted WS: Surgical Papers. Baltimore, Johns Hopkins Press, 1924, p 103. 8. Marcus RT, Foster WD: Observations on the clinical features, aetiology and geographical

the

commonly occurring Staphylococ¬

was

to the mark in 1947 when he

=

cus

tissue parasites as well as preexisting suboptimal health and nutrition in patients recently arrived from trop¬ ical areas should raise the index of suspicion in US clinicians encounter¬ ing patients with relevant signs and symptoms. It would be interesting to know whether pyomyositis is diag¬ nosed more frequently in the semitropical areas of the United States such as southern Florida and Loui¬ siana.

Thus, Robert T. Burkitt

Trichinella.

t F = filaria. Toxocara-Ascarls antigen. /

chocerca, Dracunculus, Toxocara). There has also been speculation that

cates the existence of a tropical etiologic agent necessary for abscess for¬ mation to occur, but the possibility of

likely close

put forward

the hypothesis that deep muscle abscesses in the tropics are primarily caused by the localized lowering of the vitality of muscle tissue by one of several factors such as trauma or filaria infection; that this area becomes secondarily infected by patho¬ genic organisms circulating in the blood stream and that such a condition is espe¬ cially frequent in people whose general re¬ sistance has been lowered by chronic illhealth.11

It

is

clear

that

the

primary surgi¬

treatment of this condition is

cal drainage of the abscess(es), with antibiotics (especially those effec¬ tive against penicillinase-producing

staphylococci) playing an important but secondary role. With appropriate treatment, mortality is very low, and residual deformity unlikely.

Rather than considering pyomyo¬ sitis an exotic tropical disease, US clinicians should be alerted by the ar¬ ticle by Echeverría and Vaughn to look for and appropriately diagnose and treat this rare but geographically well-distributed condition. STEPHEN C. JOSEPH, MD Office of International Health Programs Harvard University 677 Huntington Ave Boston, MA 02115

References in

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distribution of pyomyositis in east Africa. East Afr Med J 45:167-176, 1968. 9. Levin MJ, Gardner P, Waldvogel FA: "Tropical" pyomyositis: An unusual infection due to Staphylococcus aureus. N Engl J Med 284:196-198, 1971. 10. Altrocchi PH: Spontaneous bacterial myositis. JAMA 217:819-820, 1971. 11. Burkitt RT: Tropical pyomyositis. J Trop Med Hyg 50:71-75, 1947.

Pyomyositis. A "tropical" disease?

Pyomyositis A article by Theriainteresting and Vaughn Echeverin this issue of the Journal (page 856) raises once again the question of the appropriat...
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