WHAT IS KNOWN AND OBJECTIVE: Intravenous sodium stibogluconate (SbV) is the mainstay of treatment for mucocutaneous leishmaniasis. Incidence of this disease is increasing in the UK, partly because of returning military personnel. SbV has a side effect profile that requires treatment interruption in up to 28% of patients. Side effects can be unpleasant and - in the case of QTc prolongation - dangerous. CASE SUMMARY: A volunteer medical worker returning from Guatemala was diagnosed with mucocutaneous leishmaniasis. Because of previous renal problems, NSAIDs were contraindicated. Severe side effects of myalgia and arthralgia would have necessitated a treatment interruption, but a trial of prednisolone gave excellent symptomatic relief. The patient's QTc, amylase and C-reactive protein also fell following initiation of steroid treatment. The SbV treatment course was completed successfully. WHAT IS NEW AND CONCLUSION: This is the first reported case of the dangerous and disabling side effects of SbV being treated very effectively with glucocorticoids. Of note is the normalization of the apparently sodium stibogluconate-induced prolongation of the QTc interval. Further investigation into this potential beneficial effect is warranted.