A 46-year-old male from Colombia with a medical history of Systemic Lupus Erythematosus and under Corticosteroids treatment (10 mg/day) presented to the emergency room with a 3 day fever of 38º and intense pain with swelling of the left knee and lower limb.
Physical exploration revealed hypotension, tachycardia, diaphoresis, agitation, limb lividity and a frankly toxic appearance. The patient was unable to remain in decubitus position due to intense pain. Blood tests revealed C-reactive protein of 27mg/dl and Procalcitonin of 2.7ng/mL. Knee arthrocentesis showed the presence of Staphylococcus.
Contrast-enhanced CT showed synovitis in both knees with bilateral joint effusion (Fig 1a, 1b and 2a) and findings compatible with myositis of the quadriceps (Fig. 1c, 1d and 2b) (fibrillar hypodensity and thickening of the vastus intermedius muscle and to a lesser extent of the vastus medialis along with intermuscular edema; no air bubbles were identified). Moreover, cellulitis extending from the inner thigh and left gluteus to the retroperitoneum was also noted (Fig 1e).
The patient underwent urgent surgical debridement of the left thigh and gluteus. Necrotizing cellulitis was present. Furthermore, right knee arthroscopy evacuated abundant purulent material. However, the patient progressed to exitus letalis after refractory hypotension and asystole.
Necrotizing fasciitis (NF) is a life-threatening and rapidly progressive deep soft-tissue infection most commonly arising from polymicrobial infection. As its prognosis depends on prompt recognition and treatment, the high mortality rates (as high as 70-80%) suggest that diagnostic delay is frequent [1, 2].
NF is most often associated with trauma or surgery but many patients have a predisposing condition placing them at increased risk for infection and death. Patients with systemic lupus erythematosus (SLE) have an inherent susceptibility augmented by the use of doses higher than prednisone 20mg/d [3], and immunosuppressives. Despite management improvements, infection still accounts for 20-50% of deaths in SLE patients [4]. Nevertheless and somewhat surprisingly, NF has been uncommonly reported.
Clinical manifestations may be deceptively benign and at onset it may not be possible to fully distinguish NF from minor soft-tissue infections. Early infection spreads widely along subdermal fascial planes with destruction occurring in fascial and subcutaneous tissues and little or no abnormality recognizable in the skin. This relatively normal appearance of the skin is often responsible for delay in diagnosis [5].
NF remains a clinical diagnosis. Imaging is useful to define disease extent, aid in planning the surgical approach, and exclude other conditions. Imaging examination should in any case delay treatment in severely toxic patients [6]. CT features depict dermal thickening, inflammatory fat stranding, increased soft-tissue attenuation and superficial or deep crescentic fluid or air in the subfascial planes [7]. Contrast-enhanced CT usually shows no clear fascial enhancement due to necrosis. Importantly, the CT hallmark of soft-tissue air with deep fascial fluid collections is not always present and its absence should not prompt exclusion of NF as the patient may have early stages of the disease, in which gas has not yet formed or reached detectable levels [8]. CT is the most sensitive modality for soft-tissue gas detection.
Regarding MRI, T1-weighted sequences usually show subtle abnormality with loss of muscle texture and may show high-signal intensity compatible with intramuscular haemorrhage. T2-weighted MRI usually depicts subcutaneous and intramuscular oedema in a reticulated pattern as well as subfascial and interfascial crescentic fluid collections.
In conclusion, NF is a rare infection that must be recognized early if the outcome is to be favourable. Raised awareness is warranted particularly among SLE patients who are immunosuppressed by virtue of their underlying disease, therapy, or both [9]. In the absence of penetrating trauma or iatrogenic causes, gas tracking along fascial planes in a septic patient is virtually pathognomonic.
Necrotizing Lupus-related Fasciitis
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
CT axial plain scan and contrast-enhanced sequences demonstrate significant swelling of the soft tissue around the left femur, showing thickened subcutaneous tissue and increased density. Flocculent changes are visible within the fat layer in certain areas. In some regions, suspected gas density can be seen in the deep fascial plane or fascial compartments (indicated by the red arrow), along with irregular fluid-density areas, suggesting potential fluid or abscess collection within the fascia or soft tissues. Because the affected area is extensive and the gas may track into deeper fascial compartments, in combination with the patient’s clinical symptoms and immunosuppressed state, necrotizing fasciitis must be highly suspected.
Although there is swelling in the knee joint region, there are currently no apparent signs of bony destruction on the images. Only the soft tissue structures appear involved, and there is no obvious sign of joint effusion (supplemented by actual imaging findings if necessary).
Considering the patient’s underlying disease (systemic lupus erythematosus with long-term steroid use) and clinical presentation (acute onset, fever, pain), necrotizing fasciitis is most typical and poses the greatest risk.
Based on the patient’s clinical presentation (sudden high fever, severe pain, swelling), imaging findings (gas in deep fascia or fascial compartments and fluid-density areas), and immunosuppressed status (long-term steroid therapy for SLE), necrotizing fasciitis is the most likely diagnosis.
Further confirmation should be sought through laboratory tests (e.g., WBC count, CRP, muscle enzymes, blood or tissue cultures) and surgical exploration to determine the nature and extent of the lesion.
Disclaimer: This report is solely a reference analysis based on the current imaging findings and provided information. It does not replace in-person consultation or professional medical advice. Specific treatment decisions should be made in conjunction with clinical evaluations and under the guidance of qualified healthcare professionals.
Necrotizing Lupus-related Fasciitis
