Background Noonan Syndrome is caused by variants in a variety of genes found in the RAS/MAPK pathway. As more causative genes for Noonan Syndrome have been identified, more phenotype variability has been found, particularly congenital heart defects. Here, we report a case of dilated coronary arteries in a pediatric patient with a RIT1 variant to add to the body of literature around this rare presentation of Noonan Syndrome.  Case presentation A 2-month-old female was admitted due to increasing coronary artery dilation and elevated inflammatory markers. Rapid whole genome sequencing was performed and a likely pathogenic RIT1 variant was detected. This gene has been associated with a rare form of Noonan Syndrome and associated heart defects. Diagnosis of the RIT1 variant also gave reassurance about the patient’s cardiac findings and allowed for more timely discharge as she was discharged to home the following day.  Conclusions This case highlights the importance of the association between dilated coronary arteries and Noonan syndrome and that careful cardiac screening should be advised in patients diagnosed with Noonan syndrome. In addition, this case emphasizes the importance of involvement of other subspecialities to determine a diagnosis. Through multidisciplinary medicine, the patient was able to return home in a timely manner with a diagnosis and the reassurance that despite her dilated coronary arteries and elevated inflammatory markers there was no immediate concern to her health.