Departments of 1 Nephrology, 2 Dermatology and 3 Microbiology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
Introduction
Skin disorders are prevalent among kidney graft recipients. The development of dark-blue or purplish nodules on the lower limbs evokes a diagnosis of Kaposi sarcoma. We report on a patient with this presentation in whom skin biopsy led to a completely different diagnosis.
Case
A 65-year-old Caucasian woman presented to the transplant clinic with multiple purple-blue, slightly tender, about 0.5 cm diameter, subcutaneous nodules on the left leg. A diagnosis of Kaposi sarcoma was suspected. In 1991, she had undergone a successful cadaveric renal transplantation for end-stage renal disease due to nephronophthisis. Maintenance immunosuppression consisted of cyclosporin (125 mg b.i.d), azathioprine (50 mg o.d), and prednisolone (7.5 mg o.d). Post-transplantation course was uneventful except for the reactivation of hepatitis B. Eight years later, a small brownish nodule was removed from her left leg by a dermatologist and was histologically ascertained as a dermatofibroma. One week later, multiple nodules developed on the same leg and progressively increased in size (Figure 1). The patient did not report any previous trauma or insect bite at those sites. There were no systemic symptoms.
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Biopsy of one of the nodules disclosed granulomatous inflammation surrounded by lymphocytes, histiocytes, many neutrophils and giant cells (Figure 2). Auramine staining showed multiple fluorescent bacilli, acid-resistant on Ziehl staining (Figure 3
). Cultures revealed a pure growth of non-tuberculosis mycobacteria, identified as Mycobacterium chelonae, resistant to refampicin and quinolones, but sensitive to clarithromycin.
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Discussion
In this transplanted patient presenting with purple-blue nodules on the lower limb, a diagnosis of M. chelonae cutaneous infection was established by histological examination and specific cultures of a biopsy sample. The diagnosis was further confirmed by the response to clarithromycin.
Diseases caused by non-tuberculosis mycobacteria are increasingly recognized in immunocompromized hosts as well as in immunologically competent patients. Those organisms are responsible of localized skin, soft-tissue, or bone lesions following a traumatic injury with soil contamination [2,3].
Classification of non-tuberculosis mycobacteria is based on both growth rate and colony appearance on culture [4]. When the organism takes 7 days or more to grow, it is considered as a slow growing species. This category is further subdivided according to light-induced colouring. If the colonies produce pigment only after exposure to light, they are called photochromogens (type 1). If they become strongly pigmented, even if grown in the dark, they are called scotochromogens (type 2). If they do not get pigmented under light, they are called non-photochromogens (type 3). When the organism grows in less than 7 days, it is considered as a rapid growing species (type 4). M. chelonae as well as M. abcessus and M. fortuitum belong to this latter category, also called Mycobacterium fortuitum complex. M. chelonae infection usually manifests as multiple skin nodules on the lower limbs. It most often affects immunocompromized patients but has also been reported in immune competent individuals in the setting of post-traumatic wound, catheter-related, and corneal infections. Patients are most often asymptomatic except for the local discomfort due to the lesions [4].
In renal-transplant recipients, only three cases of M. chelonae infections have been reported [57]. One of them developed M. chelonae bacteraemia with fever and subcutaneous nodules following thoracic duct drainage; infection responded to cefoxitin. The two others presented with an infection limited to the skin and were successfully treated with cefotoxin in one case and sulphonamides in the other. In all three cases the diagnosis was only made after histological and microbiological investigation.
As illustrated in our patient, the purple-blue coloration of cutaneous nodules due to M. chelonae may simulate Kaposi sarcoma. Once the diagnosis of mycobacteria cutaneous infection has been established, identification of the subtype is mandatory, as drug susceptibility is species-dependent [8]. M. chelonae are reported to be sensitive to tobramycin, clarithromycin, and amikacin in 70%, to imipenem in 60% and to doxycycline and ciprofloxacin in 25% of cases [4]. In our patient, however, the organism was only sensitive to clarithromycin.
The origin of the contamination in our patient remains unclear. She might have been contaminated through cutaneous inoculation of the organism during the removal of the dermatofibroma. Indeed, water and water-based solutions have been incriminated in some cases of nosocomial infections with non-tuberculosis mycobacteria [8,9]. Infection with M. abcessus, another species of non-tuberculosis mycobacteria, has been reported in 71 patients after local anaesthesia with xylocaine solution aspirated from a previously opened inadequately stored vial [8].
Teaching point
Mycobacterium chelonae is a rare cause of cutaneous infection in renal transplant recipients. Its presentation as purple-blue nodules may simulate Kaposi sarcoma. Histological and microbiological examination is required both to establish the diagnosis and select the appropriate treatment.
Acknowledgments
We thank Mrs Degraux Josiane for technical assistance.
Notes
Supported by an educational grant from
Correspondence and offprint requests to: Dr David Verhelst, Department of Nephrology, Saint-Luc Academic Hospital, Avenue Hippocrate 10, B-1200 Brussels, Belgium.
References