This case report describes a 34-year-old male with AML, intermediate risk, initially treated with standard 7+3 induction chemotherapy followed by high-dose cytarabine consolidation. Despite achieving medullary remission, minimal residual disease(MRD) persisted. The patient underwent allogeneic-HSCT from an HLA-matched sibling donor. At the 33rd-month post-transplant, the patient, in full donor chimerism, developed a pituitary macroadenoma and hypopituitarism, alongside CNS relapse and medullary remission was confirmed in the bone marrow. Management included cranial radiotherapy and pituitary hormone replacement. Subsequent bone marrow relapse was treated with salvage chemotherapy (high-dose cytarabine and mitoxantrone), achieving medullary remission. Persistent CNS disease necessitated intrathecal triple therapy until cerebrospinal fluid clearance. MRI response was also obtained.

A second allogeneic HSCT was performed from the same donor using a myeloablative FLU-TBI conditioning regimen. GVHD prophylaxis consisted of Cyclosporine-A and Methotrexate. On post-transplant day +25, the patient presented with severe cutaneous manifestations with some bullous lesions initially suspected as aGVHD or drug eruptions. The patient was initiated on a high-dose corticosteroid (2 mg/kg prednisolone) as a primary treatment. However, due to an inadequate response, ruxolitinib(10 mg twice-daily) was added to the treatment regimen after the first week. Dermatological evaluation raised suspicion of SJS, leading to IVIG administration. The skin biopsy report indicated the possibility of grade 2 GVHD, although the possibility of a drug reaction could not be excluded. Significant clinical improvement was observed within one week of ruxolitinib initiation. Corticosteroids were tapered over six weeks to physiological replacement doses. Ruxolitinib was continued for 56 days before gradual discontinuation. Cyclosporine was maintained with target trough levels of 100-250 ng/mL and discontinued on day +90 post-transplant. This case highlights the diagnostic challenges in differentiating aGVHD in the post-HSCT setting from SJS/TEN-like presentations. It emphasises the importance of rapid intervention and the potential efficacy of JAK inhibitors in steroid-resistant cutaneous GVHD.