Introduction: Immune reconstitution inflammatory syndrome (IRIS) is an important complication after initiation of antiretroviral therapy associated with considerable morbidity and mortality in HIV patients,  but has been rarely reported in solid organ transplant patients. IRIS is a host response resulting in paradoxical worsening of an infectious disease which occurs after reversal of an immunosuppressed state. Although a working paradigm of the pathophysiology of IRIS occurring in the posttransplant setting has not been established, current evidence suggests an imbalance between pathogen directed host inflammatory (Th1, Th17) and anti-inflammatory (Th-2, Tregs) effector cells resulting in hyperinflammatory response to a pathogen with ensuing tissue damage.

Objetives: To describe a case of IRIS in a renal transplant patient with molluscum contagiosum highlighting the difficulty in differential diagnoses and the importance of early detection.

Case report: A 41 year-old male patient with accelerated hypertension received a cadaveric graft on October 2012.  IS: Tacrolimus Mycophenolate Mofetil and steroids. On October 2015 he presented seizures with ischemic  lesions in MRI whith normal CSF  and deep vein thrombosis in leg for which he began anticoagulation. Consulted in January 2021 for hiporexia with marked weight loss, diarrhea and fever,  presenting severe gingival hyperplasia with loss of teeth of months of evolution and  cutaneous  umbilical papular lesions in neck, face and limbs. Laboratory: creat 1.7 mg/dl, WBC 3100, Htc 28, platelets and hepatic enzimes  normal,  COVID PCR, Cryptococcal  antigenemia and CMV PCR negative,  parvovirus, HIV, VDRL, HBV and HCV negative . Tacrolimus was stopped (dosages of 19 ng/ml) remaining with hydrocortisone 100 mg every 8 hours. Control at 24 hs: WBC 1900 with 55 % NTF, Htc 28 Platelets 178000; colony stimulation factor and Ganciclovir were indicated. Chest CT: emphysema without infiltrates. Biopsy of oral lesions compatible with gingival hyperplasia due to drugs, probably secondary to tacrolimus. Biopsy of limb lesions: molluscum contagiosum. Tacrolimus was switched to rapamycin, and he contnued with steroids. On the 16 th day he was readmitted due to exacerbation of skin lesions and fever, coinciding with an increase in CD4 and improvement of blood analysis. The picture was interpreted as IRIS, increasing doses of steroids to 20 mg/day, improving the picture until healing of skin lesions.

Conclusions: Our study highlights the clinical relevance of recognising IRIS in patients transplanted with solid organs through the exacerbation of skin lesions.