Obesity and Hypertension in a Child: Don't Forget the Workup

Introduction: We report a rare case of membranous nephropathy (MN) with monoclonal (IgG1) deposits in a pediatric patient presenting with hypertension. Case Description: A 17-year-old obese female (BMI > 98th%) was referred by psychiatry for elevated blood pressures persisting after discontinuing ADHD medications. Urinalysis showed > 300gm of protein with urine protein/creatinine ratio 3.1 and confirmed on repeat lab. Serum chemistries were normal with a creatinine of 0.59 mg/dL and serum albumin of 3.5. Her CBC, C3-C4, ANA, metanephrine, renin, aldosterone, TSH, PLA2R, HIV, hepatitis B and C panels were normal. A kidney biopsy showed focal sclerosing immune complex mediated glomerulonephritis with IgG1 kappa deposits, C3 co-dominant with IgG staining and monotypic kappa light chain immunofluorescence (IF) staining (Fig 1). IF microscopy was repeated on paraffin-embedded tissue sections and revealed minimal staining for IgG, C3, and C1q, with kappa light chain restriction. IgG subclasses demonstrated 3+ staining with IgG1 no staining with IgG 2, IgG 3, and IgG 4. She was referred to oncology. Serum and urine protein electrophoresis did not show any monoclonal protein. Bone marrow biopsy with FISH done for multiple myeloma panel and plasma cell enrichment was normal. She does not seem to have monoclonal gammopathy of renal significance/overt hematological malignancy/ autoimmune disease or an infectious etiology. Discussion: MN can be an uncommon cause of nephrotic range proteinuria in the pediatric population and usually has polyclonal IgG deposits. MN with monoclonal Ig deposits (MIDD) is rare and has not been reported in the pediatric population. Guiard et al and Rocha et. al reviewed 21 & 28 adult cases and proposed an algorithm for a thorough workup for these cases. However, treatment for idiopathic MIDD cases as seen with this patient remains uncertain. We should pursue a workup for hypertension even with obvious secondary causes like obesity and ADHD medications.Oncological workup is necessary if MIDD is noted on the biopsy.Fig1: IgG 1 (3+) within the glomeruli