COQ2 Nephropathy: A Newly Described Inherited... : Journal of the American Society of Nephrology (original) (raw)

CLINICAL RESEARCH

A Newly Described Inherited Mitochondriopathy with Primary Renal Involvement

Diomedi-Camassei, Francesca*; Di Giandomenico, Silvia†; Santorelli, Filippo M.†; Caridi, Gianluca§; Piemonte, Fiorella‡; Montini, Giovanni¶; Ghiggeri, Gian Marco§; Murer, Luisa¶; Barisoni, Laura‖; Pastore, Anna†; Muda, Andrea Onetti††; Valente, Maria Luisa**; Bertini, Enrico†; Emma, Francesco‡‡

Divisions of Pathology*, Molecular Medicine†, and Biochemistry‡, Department of Laboratory Medicine, and ‡‡Division of Nephrology and Dialysis, Department of Nephrology and Urology, Bambino Gesu[Combining Grave Accent] Children's Hospital and Research Institute, and ††Department of Pathology, La Sapienza University, Rome, §Laboratory on Pathophysiology of Uremia, G. Gaslini Institute, Genoa, and ¶Department of Pediatrics, Division of Nephrology, Dialysis and Transplantation, and **Institute of Pathology, Azienda Ospedaliera-University of Padua, Italy; and ‖Department of Pathology, New York University, New York, New York

Correspondence: Dr. Francesca Diomedi-Camassei or Dr. Francesco Emma, Division of Pathology and Division of Nephrology, Bambino Gesu[Combining Grave Accent] Children's Hospital and Research Institute, Piazza S. Onofrio 4-00165 Rome, Italy. Phone: +39-06-6859-2740; Fax: +39-06-6859-2602; E-mail: [email protected] and [email protected]

Accepted May 22, 2007

Received August 7, 2006

Abstract

Primary coenzyme Q10 (CoQ10) deficiency includes a group of rare autosomal recessive disorders primarily characterized by neurological and muscular symptoms. Rarely, glomerular involvement has been reported. The COQ2 gene encodes the para-hydroxybenzoate-polyprenyl-transferase enzyme of the CoQ10 synthesis pathway. We identified two patients with early-onset glomerular lesions that harbored mutations in the COQ2 gene. The first patient presented with steroid-resistant nephrotic syndrome at the age of 18 months as a result of collapsing glomerulopathy, with no extrarenal symptoms. The second patient presented at five days of life with oliguria, had severe extracapillary proliferation on renal biopsy, rapidly developed end-stage renal disease, and died at the age of 6 months after a course complicated by progressive epileptic encephalopathy. Ultrastructural examination of renal specimens from these cases, as well as from two previously reported patients, showed an increased number of dysmorphic mitochondria in glomerular cells. Biochemical analyses demonstrated decreased activities of respiratory chain complexes [II+III] and decreased CoQ10 concentrations in skeletal muscle and renal cortex. In conclusion, we suggest that inherited COQ2 mutations cause a primary glomerular disease with renal lesions that vary in severity and are not necessarily associated with neurological signs. COQ2 nephropathy should be suspected when electron microscopy shows an increased number of abnormal mitochondria in podocytes and other glomerular cells.