Membranous Nephropathy in a Patient with Charcot-Marie-Tooth Disease: Association of Myelin Mutations

A 40-year-old female presented to the neurologist with gradually progressive weakness of distal and proximal muscles of both lower limbs and cramps for 2 years. She gave a history of similar illness in her paternal grandmother and her father. Her examination revealed bilateral foot drop and mild proximal muscle weakness. She was diagnosed to have peripheral neuropathy and subsequently treated conservatively. Over the next year, she noticed progressive swelling of both lower limb and frothy urine. A nephrology consultation was obtained, and a renal biopsy was done, which showed membranous nephropathy. She was started on steroids and subsequently on tacrolimus as the proteinuria progressively worsened. Her anti-phospholipase A2 receptor antibody was negative both in blood and in the kidney biopsy tissue. A search for a genetic basis of this rare clinical condition was made, and heterozygous mutation was detected in the myelin gene. This mutation was confirmed with genetic sequencing. The mutation is associated with MPZ gene and is associated with multiple hereditary sensorimotor neuropathy. MPZ knockout mice have been shown to have increased glomerular permeability and proteinuria.