Evidence of ongoing complement activation on adipose tissue from an 11-year-old girl with Barraquer-Simons syndrome

Barraquer-Simons syndrome (BSS), a form of acquired partial lipodystrophy, is a rare condition characterized by gradual loss of adipose tissue from the upper body, keeping intact the white adipose tissue of the lower extremities. The etiology of BSS is not well understood, and clinical follow-up studies have not been assessed in these patients. Moreover, no histological studies have been conducted during the active phase of the disease, and complement system activation products have not been sought in the affected areas. The objective of this work was to analyze the clinical, immunological and histological events in an 11-year-old girl with BSS over a 5-year follow-up period. Clinical data were collected during six regular visits for a time period of 5 years. The circulating levels of C3, C3adesArg (a product released upon C3 activation), C4 and immunoglobulins (Ig) were quantified in serum while fat tissue from lipoatrophic areas was examined by immunohistochemical and immunofluorescence approaches. In her regular visits, no clinical or laboratory abnormalities had been observed in the patient, except for the progression of lipoatrophy linked to the C3 hypocomplementemia and the occurrence of C3 nephritic factor. Adipose tissue from the patient showed atrophied and dead adipocytes, an abnormal production of extracellular matrix, and a remarkable accumulation of infiltrating CD68 macrophages and adipocyte precursors (marked by c-Kit positiveness). Simultaneous detection of IgG, C3, C5a and C5b-9 proved the ongoing complement activity and complement-directed injury within the adipose tissue. Our results showed the first evidence that the complement system hyperactivation occurs within the adipose tissue and is linked with fat loss in patients with BSS.