Li Lei1, Gia Oh2, Scott Sutherland3, Graham Abra4, John Higgins1, Richard Sibley1, Megan Troxell1, Neeraja Kambham5. 1. Department of Pathology, Stanford University, H2110, 300 Pasteur Drive, Stanford, CA, 94305, USA. 2. Randall Children's Hospital, Portland, OR, USA. 3. Department of Pediatrics & Division of Nephrology, Stanford University, Stanford, CA, USA. 4. Satellite Healthcare, San Jose, CA, USA. 5. Department of Pathology, Stanford University, H2110, 300 Pasteur Drive, Stanford, CA, 94305, USA. nkambham@stanford.edu.
Abstract
BACKGROUND: Myelin figures, or zebra bodies, seen on electron microscopy were historically considered pathognomonic of Fabry disease, a rare lysosomal storage disorder caused by alpha-galactosidase A deficiency and associated with X-linked recessive mode of inheritance. More recently, iatrogenic phospholipidosis has emerged as an important alternate cause of myelin figures in the kidney. METHODS: We report two families with autosomal dominant nephropathy presenting with proteinuria and microscopic hematuria, and the kidney biopsies were notable for the presence of myelin figures and zebra bodies. RESULTS: Laboratory and genetic work-up for Fabry disease was negative. Genetic testing in both families revealed the same heterozygous missense mutation in LMX1B (C.737G>A, p.Arg246Gln). LMX1B mutations are known to cause nail-patella syndrome, featuring dysplastic nails and patella with or without nephropathy, as well as isolated LMX1B-associated nephropathy in the absence of extrarenal manifestations. CONCLUSIONS: LMX1B mutation-associated nephropathy should be considered in hereditary cases of proteinuria and/or hematuria, even in the absence of unique glomerular basement membrane changes indicative of nail-patella syndrome. In addition, LMX1B mutation should be included in the differential diagnosis of myelin figures and zebra bodies on kidney biopsy, so as to avoid a misdiagnosis.
BACKGROUND: Myelin figures, or zebra bodies, seen on electron microscopy were historically considered pathognomonic of Fabry disease, a rare lysosomal storage disorder caused by alpha-galactosidase A deficiency and associated with X-linked recessive mode of inheritance. More recently, iatrogenic phospholipidosis has emerged as an important alternate cause of myelin figures in the kidney. METHODS: We report two families with autosomal dominant nephropathy presenting with proteinuria and microscopic hematuria, and the kidney biopsies were notable for the presence of myelin figures and zebra bodies. RESULTS: Laboratory and genetic work-up for Fabry disease was negative. Genetic testing in both families revealed the same heterozygous missense mutation in LMX1B (C.737G>A, p.Arg246Gln). LMX1B mutations are known to cause nail-patella syndrome, featuring dysplastic nails and patella with or without nephropathy, as well as isolated LMX1B-associated nephropathy in the absence of extrarenal manifestations. CONCLUSIONS:LMX1B mutation-associated nephropathy should be considered in hereditary cases of proteinuria and/or hematuria, even in the absence of unique glomerular basement membrane changes indicative of nail-patella syndrome. In addition, LMX1B mutation should be included in the differential diagnosis of myelin figures and zebra bodies on kidney biopsy, so as to avoid a misdiagnosis.
Authors: Filippo Pinto E Vairo; Pavel N Pichurin; Fernando C Fervenza; Samih H Nasr; Kevin Mills; Christopher T Schmitz; Eric W Klee; Sandra M Herrmann Journal: BMC Nephrol Date: 2020-08-13 Impact factor: 2.388