Diagnosis of Congenital and Acquired Generalized Lipodystrophies—Similarities and Differences

Generalized lipodystrophies (GLs) are rare diseases characterized by a lack of body fat. When patients with a GL phenotype are referred with a presumptive diagnosis of congenital generalized lipodystrophy (CGL) but genetic testing for known pathogenic variants is negative, the diagnosis of acquired generalized lipodystrophy (AGL) becomes a more likely diagnosis. No single test confirms such a diagnosis, and it is crucial to recognize the similarities and differences between these diseases. We review the literature and report four GL cases from our lipodystrophy outpatient clinic, highlighting the main points for an accurate diagnosis. Similarities: phlebomegaly, umbilical scar protrusion, loss of Bichat’s fat pad, muscle hypertrophy, and hepatomegaly can occur in both. Cirrhosis can also arise, but in AGL, it occurs as a consequence of hepatic steatosis and also due to autoimmune hepatitis. Insulin resistance is frequent, and patients present acanthosis nigricans and acrochordons and may develop difficult-to-control diabetes and its complications, despite very high daily doses of insulin. Low HDL and hypertriglyceridemia are frequent and may progress to acute pancreatitis. Serum leptin levels are typically low and contribute to hyperphagia. Differences: AGL patients’ body fat loss occurs gradually in childhood or adolescence, whereas CGL patients are born with the characteristic phenotype. Evaluating photographs of AGL patients in the first years of life can provide evidence of this selective and gradual fat loss. Some AGL patients may have panniculitis (inflamed and painful subcutaneous nodules), with or without autoimmune diseases. In conclusion, recognizing both similarities and differences is crucial for making an accurate diagnosis and ensuring the most appropriate treatment.