When Vasculitis Masks a Flesh-Eating Infection: Rare Case Reveals Diagnostic Traps

A rare and treacherous collision of two serious diseases has been documented in a new case report published in Clinical Case Reports, describing a 38-year-old woman with polyarteritis nodosa who developed necrotizing fasciitis, the rapidly progressive soft tissue infection often described in the public imagination as a flesh-eating disease. The case is striking not only because of the rarity of the combination, but because the underlying vasculitis and the patient’s immunosuppressive treatment created a clinical picture so ambiguous that standard diagnostic scores and laboratory markers pointed in the wrong direction. The report offers a detailed account of how clinicians navigated the overlap between chronic inflammatory disease and acute life-threatening infection, and why the authors argue that clinical judgment must sometimes override scoring systems when a patient is deteriorating in front of the medical team.

Polyarteritis nodosa, or PAN, is a necrotizing vasculitis that attacks medium-sized and small arteries. The inflammation of the vessel walls can lead to occlusion of the arteries, cutting off blood supply to the tissues they serve and producing ischemia, ulceration, and tissue death. In this patient, the disease had already announced itself in dramatic fashion: for a month before her acute deterioration, she had suffered recurring necrotic, weeping sores across her feet, thighs, arms, and torso. An earlier histopathological evaluation had confirmed the diagnosis, showing prominent involvement of small and medium-sized vessels with acute inflammation and fibrinoid necrosis, the characteristic pattern of vessel wall destruction seen in PAN, with no granulomas or malignancy to suggest an alternative explanation. Her lesions were further complicated by what the treating team described as diffuse pyoderma gangrenosum, another ulcerating condition that can accompany systemic disease and that further muddied the diagnostic waters.

The acute crisis began with burning pain, redness, and swelling in the third and fourth digits of her right hand. She had already completed fourteen days of vancomycin and sulzone therapy without any improvement in her ulcers, an early warning that something beyond ordinary cellulitis was at work. Over the following four days, the symptoms spread relentlessly from the fingers to the entire hand and forearm. When clinicians examined her, they found erythema, swelling, severe pain, skin discoloration, fluid-filled bullae, and frank necrosis covering the hand and forearm, with ulcers on the palm leaking pus. This constellation of findings, particularly the pain that appeared disproportionate to the visible findings and the rapid tissue destruction, raised the immediate suspicion of necrotizing fasciitis, an infection of the fascial planes that can advance by the hour and cause systemic toxicity and multi-organ failure if not treated urgently.

The differential diagnosis in such a presentation is broad and unforgiving. The team considered severe cellulitis, a pyoderma gangrenosum flare in the setting of active PAN, compartment syndrome, clostridial myonecrosis, and even chronic conditions such as hypopigmented mycosis fungoides, though the acute tempo made the latter unlikely. Compartment syndrome was initially entertained because of the marked swelling and pain in the limb, but the clinical course and operative findings pointed instead toward a necrotizing soft tissue infection. Gas gangrene was judged less likely because there was no crepitus and imaging did not suggest gas in the soft tissues. Severe cellulitis, too, fell away as a leading explanation once the disproportionate pain, the bullae, and the intraoperative appearance of devitalized tissue were weighed together. The decisive combination was the severe acute onset, the purulent material, the systemic inflammatory reaction, and the prompt improvement that followed emergency surgery and broad-spectrum antibiotics.

Laboratory investigations told a deliberately confusing story. Her erythrocyte sedimentation rate was elevated at 59 millimeters per hour, and her white blood cell count showed striking leukocytosis at 28.8 times ten to the ninth per liter, a figure that fell after surgery and antimicrobial therapy in keeping with clinical improvement. Yet her C-reactive protein remained largely within the normal range despite the severity of the infection, and her LRINEC score, a laboratory risk indicator designed to identify necrotizing fasciitis, was only 3, well below the threshold that would suggest the diagnosis. Complement levels were normal, blood cultures showed no bacterial growth after five days, and immunofluorescence studies for IgG, IgA, IgM, C1q, and C3 were negative. Doppler ultrasound demonstrated subcutaneous edema in the affected limb, and ultrasound findings were supportive of necrotizing fasciitis. The authors emphasize that these results highlight a critical lesson: individual inflammatory markers may be nondiagnostic, and necrotizing fasciitis should not be excluded solely on the basis of a normal CRP or a low LRINEC score when the clinical presentation is concerning.

The reasons this patient was so vulnerable to such an infection form a central thread of the report. Her long-term corticosteroid therapy with prednisolone for active arthritis suppressed her immune system, and she had also received cyclophosphamide, a potent immunosuppressant, as part of her PAN treatment, with monthly injections and methylprednisolone among the medications that may have predisposed her to severe soft tissue infection. She additionally had a history of treated hepatitis C. The vasculitis itself had damaged her peripheral veins to the point that intravenous drugs had to be delivered through a central venous catheter to ensure reliable access. Together, these factors created what the authors describe as an ideal setting for necrotizing fasciitis to develop, underscoring the need for close monitoring in high-risk populations whose immune defenses have been deliberately or pathologically blunted.

Treatment proceeded along the lines that guidelines for necrotizing fasciitis demand, and the sequence mattered. Because of the marked limb swelling and concern about rising compartment pressures, an emergency fasciotomy was performed first to relieve tissue pressure, followed by surgical debridement of devitalized tissue, the acknowledged cornerstone of therapy for this infection. Broad-spectrum intravenous meropenem and levofloxacin were continued postoperatively, with tramadol for pain control and enoxaparin to prevent thrombosis during the recovery period. Negative-pressure wound therapy, commonly known as VAC therapy, was instituted to promote healing and granulation tissue formation, and once healthy granulation tissue had developed and the infection was controlled, the wound was closed by secondary closure without the need for skin grafting. The patient also received clotrimazole for vaginal thrush, a reminder of how immunosuppressed patients can acquire secondary infections even as the primary crisis is being managed.

The outcome was favorable, and the trajectory is instructive. The patient remained clinically stable throughout her postoperative course, was discharged after a five-day hospital stay with instructions for continued wound care, and achieved complete wound healing within approximately three weeks, with no evidence of recurrent infection at follow-up. At her ten-day follow-up she showed significant improvement and no signs of infection. The authors note that the good clinical response to prompt surgical intervention and antimicrobial therapy supports the accuracy of the clinical diagnosis, even though the workup had important gaps. Tissue culture and susceptibility testing were not available, so the causative pathogen was never microbiologically confirmed and therapy remained empiric. Advanced cross-sectional imaging with CT or MRI to delineate the extent of fascial involvement was also not performed, because the team judged that in a patient deteriorating this quickly, delaying definitive management for advanced imaging would have been the greater risk.

Necrotizing fasciitis remains rare, with an estimated incidence of roughly one to two cases per 100,000 person-years, though reported rates vary geographically. The most commonly implicated pathogens are Group A Streptococcus and Staphylococcus aureus, including methicillin-resistant strains, and the infection can be monomicrobial or polymicrobial. Large bullae filled with bloody or yellowish fluid can occur, as in this patient, although the blackened necrotic lesions classically associated with the disease are not always present, and skin darkening is another hallmark. Untreated infection can spread to deeper structures including nerves, causing nerve damage and reduced sensation, and blisters with gas formation suggest Clostridium species. Skin and blood cultures remain critical for pathogen identification, although they may fail, as they did here. The case stands as a vivid reminder that in immunocompromised patients with underlying vascular disease, histological evidence, early clinical recognition, vigorous surgical care, and targeted antimicrobial therapy together form the difference between recovery and catastrophe, and that no laboratory score should be allowed to overrule an experienced clinician’s alarm.

Subject of Research: Necrotizing fasciitis occurring in a patient with polyarteritis nodosa

Article Title: Rare Case of Necrotizing Fasciitis With Polyarteritis Nodosa in a Multi‐Comorbid Patient

Article References: Hassan, S. M. S., Shahab, S. H., Raza, M., Saleem, S., Hussain, M. F., & Habib, F. (2026). Rare Case of Necrotizing Fasciitis With Polyarteritis Nodosa in a Multi‐Comorbid Patient. Clinical Case Reports, 14(10), Article e73624. https://doi.org/10.1002/ccr3.73624

Image Credits: AI Generated

DOI: 10.1002/ccr3.73624

Keywords: necrotizing fasciitis, polyarteritis nodosa, vasculitis, immunosuppression, fasciotomy, surgical debridement, LRINEC score, soft tissue infection, cyclophosphamide, corticosteroids, negative-pressure wound therapy, case report