Purpose or Case Report: To describe the radiographic appearance of subclinical calcified brown fat necrosis and to delineate the associated clinical and laboratory findings. While brown fat necrosis has been described in infants with underlying cardiac disease treated with prostaglandins, we emphasize hypotension from cardiac or respiratory arrest as a primary risk factor.
Methods & Materials: PACS was searched using keywords "soft tissue calcification" and "chest." The clinical record was searched for history of cardiac surgery, bypass, ECMO, prostaglandin use, hypoxia, age when calcifications were first detected, location, resolution, and associated hypercalcemia, thrombocytopenia, and elevated triglycerides. Renal results were evaluated for nephrocalcinosis.
Results: 5 patients were found. 3 were premature. None had skin lesions on exam. All had underlying congenital heart disease and experienced cardiac and/or respiratory arrest with hypotension between 1-6 weeks before soft tissue calcifications were detected. Single ventricle physiology was the most common lesion (1 tricuspid atresia, 2 hypoplastic left heart syndrome). 3 received prostaglandin therapy. Soft tissue calcifications occurred bilaterally in areas of brown fat in the cervical, supraclavicular, and peri-scapular soft tissues and axilla. 2 patients had resolution by 9 weeks and 5 months. Hypercalcemia was present in 3 (60%), thrombocytopenia in 2 (40%), and elevated triglycerides in all 5 (100%). Renal ultrasound was performed in all patients with 1 with nephrocalcinosis.
Conclusions: Brown fat necrosis is subclinical, diagnosed on plain film, and likely self-limited. It may be a marker of prior systemic stress. It has previously been described in term infants with congenital heart disease treated with prostaglandins. Rather than medication related, it may be related to hypoxic/ischemic insult and occurs in both term and premature infants with underlying cardiac disease who experience cardiac or respiratory arrest with hypotension. Similar to other studies, several patients demonstrated mild hypercalcemia, thrombocytopenia, and all had elevated triglycerides. However, other studies have suggested that severe hypercalcemia can occur up to 6 months of age and the radiologist can help identify patients that need to be followed. Additionally, renal ultrasound should be considered to evaluate for nephrocalcinosis.