Background: RAS guanyl-releasing protein 1 (RASGRP1) deficiency is characterized by immune dysregulation and Epstein-Barr virus (EBV)-related lymphoproliferation. Diffuse mesangial sclerosis is one of the infrequent causes of infantile nephrotic syndrome. Case Presentation: Here, we described a 7-year-old girl who was diagnosed with diffuse mesangial sclerosis at 5 months old and subsequently developed chronic bilateral neck swelling at the age of 3 years. Clinical assessment and investigations revealed a complex clinical picture, including recurrent cervical lymphadenopathy and recurrent infections. Further evaluation revealed immunological deficiencies, autoimmune lymphoproliferative syndrome-like illness, chronic EBV infection, and ultimately Hodgkin lymphoma. Genetic testing identified a RASGRP1 homozygous loss-of-function variant with both parents being carriers. Conclusion: This is the first reported case of RASGRP1 deficiency in Malaysia, and we highlight the challenges clinicians face when the disease manifests in varied presentations.