Severe hypertriglyceridemia (HTG) (>885 mg/dL) can be caused by familial partial lipodystrophy type 3 (FPLD3), an autosomal dominant disorder caused by loss of function of the peroxisome proliferator-activated receptor gamma (PPARG), characterized by abnormal distribution of fat and metabolic derangements. This case reports a 16-year-old female (body mass index, 23.5 kg/m2) hospitalized twice for pancreatitis (triglycerides [TG] level >2,200 mg/dL). Her treatment management included bowel rest, insulin infusion, and plasmapheresis. A low-fat diet with 10 g of fat daily and 160 mg of fenofibrate daily decreased fasting TG to 411 mg/dL (range, 0–149 mg/dL). The patient had a normal leptin level. Panel testing of genes that impact TG metabolism revealed a known pathogenic variant in the PPARG gene (c.452A>G p.Tyr151Cys). A second variant detected in this gene, c.1003G>C (p.Val335Leu), is considered benign. Her glycosylated hemoglobin of 6.6% and 2-hour oral glucose tolerance test confirmed type 2 diabetes mellitus (T2DM). This study reports the earliest detection of T2DM in an adolescent with a pathogenic variant of PPARG. PPARG-related FPLD3 should be considered in lean children that present with severe HTG and insulin resistance, and subsequent treatment with proliferator-activated receptor gamma agonists, specifically thiazolidinediones, should be considered.