The patient was a 48-year-old woman with no noteworthy history who complained of painful lesions that were distributed linearly on the external aspect of both thighs and had appeared 2 weeks earlier. She had undergone mesotherapy of the affected area 1 month before appearance of the lesions. Physical examination revealed fluctuating and painful subcutaneous erythematous-violaceous nodules that had given rise to abscesses and fistulas. Skin ultrasound revealed hypoechoic collections in the dermis, from which fistulas extended into subcutaneous tissue, and increased echogenicity in the areas adjacent to the lesions (Fig. 1). Doppler ultrasound showed increased vascularization around the periphery of the collections. A skin biopsy was performed, confirming panniculitis, Fite-Faraco staining revealed the presence of bacilli, and Mycobacterium abscessus was identified by polymerase chain reaction.

Figure 1

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Atypical mycobacterial panniculitis is a reported complication of mesotherapy that requires combined drug therapies, sometimes in conjunction with surgery. Skin ultrasound allows for detailed and objective evaluation of the extent and evolution of subcutaneous tissue involvement, which is often accompanied by extensive subclinical lesions. Real-time visualization of the abscessed area also enables the collection of samples by ultrasound-guided aspiration for analysis and microbiological culture.