Phosphoglyceride (PG) crystal deposition disease: a novel acquired disease in which PG crystals are deposited in injured soft tissue and bone with phospholipid metabolism disturbance.

The clinical history and crystal characteristics of three published cases and three new cases of phosphoglyceride (PG) crystal deposition disease of soft tissues and bones were compared. All patients (age range, 51-64 years) were generally healthy without a genetic background of congenital immunodeficiency or lipidosis. Foreign body granulomas grew slowly, predominantly at postoperative or repeat injection lesions. In two cases, crystals were deposited in multiple locations, and in one case, lipophage accumulations were found in the bone marrow. The crystals characteristically dissolved in acetic acid with oxygen gas formation, easily dissolved in alkalis and showed positive staining for PG by the gold hydroxamic acid method. All crystals examined by infrared microscopy, mass spectrometry and X-ray microanalysis showed similar results, supporting the theory that the crystals were PG. Phosphoglyceride deposition disease is a lipid metabolic disorder in which PG crystals are slowly deposited, predominantly in injured soft tissues, forming foreign body granulomas. The diagnosis can be based on histological characteristics. The prognosis is favorable, although some cases showed systemic depositions with repetitions. Lysosomal phosphoglyceride metabolism in macrophages might be affected.