The Clinical Diagnostics Service of the Molecular Otolaryngology & Renal Research Laboratories is a CLIA-approved, Joint Commission-accredited diagnostic laboratory that offers mutation screening of several genes.
Dense Deposit Disease (DDD, aka Membranoproliferative Glomerulonephritis Type II, MPGNII)
Association studies have linked polymorphisms in the Factor H gene (HF1, *134370) with DDD (Abrera-Abeleda et al., 2005). DDD is a kidney disease in which dense deposits form in the glomerular basement membrane. The diagnosis is made on renal biopsy: dense deposits can be seen in the glomerular basement membrane by electron microscopy; immunofluorescence is positive for C3 and negative for immunoglobulins.
Atypical Hemolytic-Uremic Syndrome
The clinical manifestations of hemolytic-uremic syndrome (HUS; 235400) include hemolytic anemia, thrombocytopenia and acute renal failure. Most cases are associated with epidemics of diarrhea caused by verocytotoxin-producing bacteria [Escherichia coli O157:H7 (Stx-HUS)].
Atypical hemolytic uremic syndrome (aHUS) is a rarer disease. It is not associated with Stx-HUS infection and neither does it present with watery, bloody diarrhea (Warwicker et al., 1997). It can be either sporadic or familial and has an extremely unfavorable prognosis, with about 50% of persons progressing to ESRD and 25% dying during the acute illness; transplantation in many survivors is unsuccessful (Schieppati et al., 1992; Taylor et al., 2004). Genetics studies have shown that approximately 50% of cases of aHUS are caused by mutations in MCP, CFH and IF (Caprioli et al., 2006). Identifying the genetic cause of aHUS is extremely important as it can help to direct clinical treatment decisions.
The CFH and related gene region is highly homologous lending itself to the high likelihood of recombination within the interval (referred to a non-homologous allelic recombination or NHAR). For example, homozygous deletions of CFHR3 and CFHR1 are considered a risk factor in aHUS and are associated with the generation of factor H autoantibodies. These autoantibodies bind to and block the C-terminal recognition region of factor H (Zipfel et al., 2007, Zipfel and Skerka 2009, Skerka et al., 2009). Rearrangements in this region can also result in the formation of hybrid proteins that are comprised of a large portion of complement factor H and a small portion of complement factor H related 1 (Venables et al., 2006, Maga et al., 2011, Eyler SJ et al., 2013).
Indications for screening
Screening is offered to persons with aHUS and biopsy-proven DDD; we will also offer screening for some other factor H-related diseases.
MORL screening methodology
Multiplex Ligation-Dependent Probe Amplification is used to detect the presence of a NHAR event that results in the deletion of CFHR3 – CFHR1. This assay is based on sequence-specific hybridization and subsequent ligation of two directly flanking half-probes on a target nucleic acid sequence. Only when these half-probes are ligated can the resultant fragment serve as a template for PCR amplification. Multiple probes are used to cross-check validity.
The standard deviation rates for each probe are 4%-10% (Schouten, J et al., 2002). MLPA has 95% confidence intervals for positive and negative predictive accuracies of 0.951-0.996 and 0.9996-1 respectively (Ahn JW et al., 2007). With the use of multiple probes, the likelihood of a spurious result is remote.
Turnaround time is approximately 3 months.
8 - 10 cc. whole blood in lavender (EDTA) top tubes OR 10 μg DNA, minimum concentration: 50 ng/μl (A260/A280 1.8-2) resuspended in 0.1mM EDTA (10mM Tris HC1, 0.1mM EDTA, pH 8, Teknova Cat#T0220).
Cost & CPT Codes
See the MORL testing menu
Kidneeds (not-for-profit foundation dedicated to the cure of DDD)
Foundation for Children with Atypical HUS
Maga TK et al.: A novel deletion in the RCA gene cluster causes atypical hemolytic uremic syndrome. Nephrol Dial Transplant. 2011 Feb; 26(2):739-41.
PubMed ID: 20974643
Abarrategui-Garrido, C. et al.: Characterization of complement factor H–related (CFHR) proteins in plasma reveals novel genetic variations of CFHR1 associated with atypical hemolytic uremic syndrome. Blood. 2009 Nov 5;114(19):4261-71
PubMed ID: 19745068
Heinen, S. et al.: De Novo Gene Conversion in the RCA Gene Cluster (1q32) Causes Mutations in Complement Factor H Associated With Atypical Hemolytic Uremic Syndrome. Hum Mutat. 2006 Mar;27(3):292-3.
PubMed ID: 16470555
Zipfel, P. et al.: Complement Regulators and Inhibitory Proteins. Nat Rev Immunol. 2009 Oct;9(10):729-40.
PubMed ID : 19730437
Ahn JW et al.: Detection of subtelomere imbalance using MLPA: validation, development of an analysis protocol, and application in a diagnostic centre. BMC Medical Genetics 2007, 8:9 doi:10.1186/1471-2350-8-9.
PubMed ID : 17338807