Purpose or Case Report: A 33-day old infant was presented to the hospital after difficulty breathing and breastfeeding. The patient had a history of hyperbilirubinemia with acute hypoxic respiratory failure, felt secondary to a mediastinal mass, severe metabollic lactic acidosis, anemia, and acute severe coagulopathy.

This patient was denied vitamin K prophylaxis at birth at discretion of the parents. Vitamin K deficency subsequently caused coagulopathy and jaundiced skin, which associate with Vitamin K Deficiency Bleeding.

Presented is a case of thymic hemorrhage in a neonate demonstrating as a mimic lesion on imaging. Further invasive work-up to distinguish etiology of mass was not required demonstrating biopsy or surgery is not always necesary for diagnostic purposes. The identified symptoms represent the potential sequelae of thymic hemorrhage.
Methods & Materials:
Results: Constrast (5 mL Isovue 300) chest CT demonstrated the anterior mediastinal mass measuring 4.3 x 5.4 cm, exerting pressure on the heart. Doppler ultrasound of chest did not demonstrate blood flow within lesion suggesting abnormality in thymus could relate to hematoma rather than a malignancy. Review of history and precedent imaging was not felt to support tumor etiology of mass, foregoing biopsy. Daily 2.5 mg of vitamin K supplementations were ordered by hematology services due to deficiency. Contrast MRI (1 mL Dotarem gadolinium) of chest two days later demonstrated the mass measuring 4.1 x 3.8 cm anterior to the heart. A 2.6 component along the right infolateral margin of the mass presented hyperintense on T1 weighted imageing while presenting hypointense on T2 weighted imaging.
Conclusions: The mediastinal mass was concluded to be a thymic hematoma. Intravenous contrast use through MRI eliminated malignancy without the need of an invasive work-up by demonstrating hyperintense T1 signal and hypointense T2 signal on lesion. Doppler ultrasound supported this diagnosis by not displaying blood flow within lesion.

The lesion had differing diagnoses throughout the work-up, including thymoma, thymic carcinoma, and a germ cell mass but did not characterize any malignant behavior. Resolution after vitamin K supplementation eliminated pathologies and confirmed hematoma diagnosis. This patient suffered respiratory distress, pleural effusions, and anemia, all of which are noted on previous reported thymic hemorrhage cases.

This study identifies proper imaging techniques/modalities to discern thymic hematoma from malignancy without the need of an invasive work-up.