Nonhealing Cellulitis in a 54-Year-Old Man with Diabetes Mellitus

IM BOARD REVIEW DAVID L. LONGWORTH, MD, JAMES K. STOLLER, MD, EDITORS STEVEN D. MAWHORTER, MD Department of Infectious Disease, Cleveland Clinic; CREDI! research interests in clinical infectious disease, travel medicine, and the immunology of infections Nonhealing cellulitis in a 54'yeai>old man with diabetes mellitus 54-YEAR'OLD MAN with type 1 (insulin- WHAT IS THE DIAGNOSIS? dependent) diabetes mellitus presents to the emergency department with a 1-week What is the most likely diagnosis in this history of fever with temperatures as high as 1 case? 103°F (39.4°C) and progressive erythema, warmth, swelling, and tenderness of his left • Improper antibiotic therapy of cellulitis medial thigh. He says he has not had any trau- • Diabetic myonecrosis ma to this area. He is admitted to the hospital • Pyomyositis and receives clindamycin 900 mg intra- • Traumatic hematoma venously every 8 hours. Though his white blood cell count declines from 22.0 to 12.0 x Improper antibiotic therapy of cellulitis 109/L, he continues to have significant pain needs to be considered but is unlikely in this and cutaneous signs consistent with cellulitis. patient. The specific bacterial etiology of cellulitis is often not known. A leading edge cul- Initial evaluation ture (not done in this case) is instructive only Blood cultures are negative. A duplex ultra- 30% of the time at best. (A leading edge cul- If cellulitis does sound scan is negative for deep vein thrombo- ture is performed by inserting a needle in the not respond sis. Plain radiographs of the left thigh show no subcutaneous tissue and aspirating the gas, foreign body, or evidence of osteomyelitis. inflamed interface between normal and cel- to antibiotics Magnetic resonance imaging (MRI) reveals lulitic tissue.) Published data indicate that in a diabetic diffuse changes in soft tissue and muscle with- clindamycin usually covers the most likely out the fascial enhancement that is consistent organisms found in typical cellulitis—staphy- patient, look with diffuse infiltrative edema or inflammato- lococci, streptococci, and rare anaerobes. for another ry disease (FIGURE 1). NO discrete abscess is Aside from diabetes mellitus, this patient noted. has no obvious immunocompromising condi- diagnosis The patient is transferred to a tertiary care tions that might limit antibiotic effectiveness. center for further management. However, in a diabetic patient, a wider range Physical examination. On admission, the of organisms may be responsible for unrespon- patient's temperature is 99.9°F {31.TC), and sive cellulitis. For example, if the cellulitis is his blood pressure is 142/84 mm Hg. His left severe, we need to consider synergistic necro- thigh is slightly red and warm, with extremely tizing cellulitis, also called synergistic non- tender "woody" induration. The balance of his clostridial myonecrosis, in which Gram-nega- examination is normal, with no evidence of tive organisms often contribute as part of a cutaneous anesthesia, nerve entrapment, or mixed aerobic and anaerobic infection. A neuropathy. Computed tomography (CT) combination of a beta-lactam and a beta-lac- performed 24 hours after his MRI scan now tamase inhibitor, such as piperacillin-tazobac- shows ring-enhancing lesions in the deep tam or ticarcillin-clavulanate or a carbapen- muscles of the medial left thigh (FIGURE 1). em, provides appropriate broader coverage. Aspiration and culture of the lesions is per- Necrotizing fasciitis, which is very simi- formed. lar to the synergistic cellulitis-myonecrosis CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 67 • NUMBER 1 JANUARY 2000 13 Downloaded from www.ccjm.org on October 1, 2021. For personal use only. All other uses require permission. IM BOARD REVIEW syndromes mentioned above, is another possi- bility. It can be caused by group A Streptococcus pyogenes, Clostridium species, or mixed aerobic and anaerobic bacteria. It typically proceeds rapidly through extreme pain to cutaneous anesthesia with bullae formation, not seen in this case.1 It should be emphasized, however, that surgical consultation with full- thickness biopsy or exploration is appropriate when patients have signs and symptoms of toxemia or the diagnosis is uncertain. Gas pro- duction in tissues is too unreliable a sign to use in ruling in or ruling out severe myocutaneous infection. Diabetic myonecrosis, an uncommon complication of diabetes mellitus, was first described in 19652 and is believed to result from atherosclerotic and diabetic microangiopathic vascular infarction of skeletal muscle. It typically involves the thigh muscles and presents with severe pain over days to weeks, evolving into a well-defined mass-like lesion. Cultures are negative and treatment is sup- portive, usually without antibiotics.3 Unfortunately, lesions recur or new ones arise in 42% of cases.4 This patient had no other diabetic Pyomyositis microangiopathic organ involvement and had has a subacute positive aspirate cultures, making diabetic myonecrosis less likely. presentation Traumatic hematomas can be difficult to differentiate from abscesses. Hematomas appear nearly identical to abscesses on CT, and become visible early on both CT and MRI. In addition, hematomas can become secondarily infected. Since the immune sys- tem mounts an acute inflammatory reaction that assists in resolving even sterile hematomas, one may even observe fever and local signs similar to those of infection. This patient did not use anticoagulants or have a history of trauma, making this possibil- FIGURE 1. Magnetic resonance imaging ity unlikely. (MRI) and computed tomographic (CT) Pyomyositis—a pyogenic infection of the studies of the patient's thigh, demon- skeletal muscle—is due to Staphylococcus strating the clinical progression of aureus in more than 90% of cases.5'6 It may pyomyositis. T1-weighted MRI (top) and arise by deeper extension from cellulitis, or by T2-weighted MRI (middle) demonstrate diffuse inflammation (bright, increased direct hematogenous seeding of the muscle. signal on T2) without focal abscess. This condition typically has a subacute pre- Bottom, CT scan the next day shows a sentation with fever, persistent severe pain, hypodense abscess (pyomyositis) medial tenderness, swelling, and "woody" induration. to the femur. In contrast, myositis with rhabdomyolysis has 22 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 67 • NUMBER 1 JANUARY 2000 Downloaded from www.ccjm.org on October 1, 2021. For personal use only. All other uses require permission. a more acute onset and muscle swelling with mimic cellulitis and does not respond to "bogginess." The most commonly infected antibiotics. Ultrasonography can also demon- muscles are those of the thigh. Pyomyositis is strate local fluid collections. However, CT uncommon hut has an increased incidence in and MRI provide much more detail and give diabetic patients.5 important information about the extent of Though classically described in patients disease and the involvement of adjacent struc- from tropical climates who are otherwise nor- tures, such as possible bony involvement in a mal, pyomyositis has been noted in immuno- case of pyomyositis due to contiguous compromised patients in temperate climates. osteomyelitis.3 In addition, an imaging test Various theories attempt to explain a geo- can pinpoint the abscess, which would facili- graphic distribution of this disease, though tate the drainage procedure. limited access to timely medical care, more A word of caution: Since severe group common in tropical locations, is plausible. A streptococcal fasciitis does not produce This case fulfills all the classic features of gas, lack of gas on radiographic studies pyomyositis in a diabetic patient in a temper- should not delay an aggressive evaluation in ate climate. cases in which necrotizing fasciitis is sus- pected.1 • WHAT IS THE EVALUATION? As in any abscess-associated infection, definitive treatment involves antibiotics and Evaluation of nonhealing cellulitis in a adequate drainage of the abscess. In our case, 2 patient with diabetes should include all aspiration and culture also confirmed the except which one of the following? presence of oxacillin-sensitive S aureus in the involved muscle, providing useful data to • Blood cultures guide antibiotic therapy. This culture result • Muscle enzyme determinations was obtained even though antibiotic therapy • Ultrasonography, CT, MRI, or all three had already been started, demonstrating the • Aspiration and culture benefit of draining abscesses therapeutically • Electromyelographic testing and diagnostically, even in patients on active Gas is an therapy. unreliable sign Blood cultures are positive in 5% to 29% Electromyelographic testing can be very of diabetic patients with pyomyositis, though helpful in diagnosing some forms of inflam- of severe it is often unclear whether positive results rep- matory myositis but does not have a role in myocutaneous resent an original bacteremia or seeding from this patient. the infected muscle.5 Conversely, autopsy infection studies found spontaneous muscle abscesses in 1 WHAT CAUSES PYOMYOSITIS? fewer than 1% of patients who died of staphy- lococcal septicemia.5 Pyomyositis may develop as a result of all Muscle enzyme determinations (ie, 3 except which one of the following? serum concentrations of creatine phosphoki- nase, aspartate, aminotransferase, lactate • Immunocompromised state dehydrogenase, and aldolase) are usually nor- • Hematogenous spread during transient mal in pyomyositis,6 in spite of extensive

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