Abstract Background: Membranoproliferative glomerulonephritis (MPGN type I, II and III) was reclassified in 2013 as MPGN and C3 glomerulopathy (C3G) based on the complement system activation mechanism. Objectives: To evaluate whether C4d, a component of the classical pathway, could be a diagnostic tool in differentiating between MPGN and C3G. Methods: We conducted a retrospective study of 15 MPGN type I, II and III and 13 minimal change disease (MCD) patients diagnosed between 2000 and 2012. C4d staining using the peroxidase method was employed. Results: Using the 2013 C3G consensus classification, the 15 MPGN types I, II and III biopsies were re-classified as MPGN (8) and C3G (7). Following C4d staining, of the 8 biopsies diagnosed as MPGN, 4 had classical pathway involvement [C1q (+), C3 (+), C4d (+)]; two had lectin pathway involvement [C1q (−), C3 (+), C4d (+)]; and, two were reclassified as C3G because the absence of C4d and C1q suggested the presence of the alternative pathway [C1q (−), C3 (+), C4d (−)]. Three of the seven C3G biopsies presented classical pathway involvement and were reclassified as MPGN. The alternative pathway was present in one of the other 4 biopsies considered to be C3G. Two C3G biopsies involved the lectin pathway and the one case of dense deposit disease had lectin pathway involvement. Conclusions: C4d staining may help to differentiate between MPGN and C3G. In addition, the lectin pathway could play a role in the pathogenesis of these glomerulopathies.

Resumen Antecedentes: La glomerulonefritis membranoproliferativa (GnMP, tipo I, II y III) fue reclasificada en 2013 como GnMP y glomerulopatía C3 (GC3) en base al mecanismo que activa el sistema del complemento. Objetivos: Evaluar si C4d, componente de la vía clásica, puede diferenciar GnMP y GC3. Métodos: Estudio retrospectivo incluyendo 15 pacientes con GnMP (tipo I, II y III) y 13 con enfermedad de cambios mínimos (CM) diagnosticados entre 2000 y 2012. Realizamos tinción renal con C4d mediante el método de la peroxidasa. Resultados: En base a la definición de GC3 consensuada en 2013, las 15 biopsias diagnosticadas como GnMP se reclasificaron como GnMP y GC3 en 8 y 7 casos respectivamente. Tras la tinción de C4d; de las 8 biopsias diagnosticadas como GnMP, 4 mostraron activación de la vía clásica [C1q (+), C3 (+), C4d (+)], 2 activación de la vía de las lectinas (VL) [C1q (-), C3 (+), C4d (+)]; y 2 fueron reclasificadas como GC3 dada la ausencia de C4d y C1q sugiriendo participación de la vía alternativa [C1q (-), C3 (+), C4d (-)]. Tres de 7 biopsias diagnosticadas de GC3fueron reclasificadas como GnMP debido a las presencia de activación de la vía clásica. La vía alternativa estuvo presente in 1 de las otras 4 biopsias consideradas GC3. VL estuvo activada en 2 de biopsias diagnosticadas de GC3 y en el único caso de enfermedad de depósitos densos. Conclusiones: C4d puede ayudar a diferenciar GnMP y GC3. La VL podría jugar un papel en la patogenia de estas glomerulopatías.

Abstract Fanconi-Bickel syndrome (FBS), also known as glycogen storage disease type XI (GSD XI), is a rare autosomal recessive disorder of carbohydrate metabolism. It is caused by mutations in the gene SLC2A2, which encodes for the facilitative glucose transporter GLUT2. Diagnosis of FBS is often delayed since the clinical features and laboratory markers often overlap with other disorders whose characteristic features include short stature, fasting hypoglycemia, postprandial hyperglycemia, hepatomegaly, hypophosphatemic rickets, and proximal renal tubular dysfunction. In this article, we present a case of FBS and its management in an African American female who initially presented with persistent proximal tubulopathy, hypercalciuria, and metabolic acidosis. We also include a recent literature review on FBS and discuss other metabolic disorders that should be considered in the differential diagnosis.