Amyloid Typing by Mass Spectrometry in Clinical Practice: a Comprehensive Review of 16,175 Samples

OBJECTIVE

To map the occurrence of amyloid types in a large clinical cohort using mass spectrometry-based shotgun proteomics, an unbiased method that unambiguously identifies all amyloid types in a single assay.

METHODS

A mass spectrometry-based shotgun proteomics assay was implemented in a central reference laboratory. We documented our experience of typing 16,175 amyloidosis specimens over an 11-year period from January 1, 2008, to December 31, 2018.

RESULTS

We identified 21 established amyloid types, including AL (n=9542; 59.0%), ATTR (n=4600; 28.4%), ALECT2 (n=511; 3.2%), AA (n=463; 2.9%), AH (n=367; 2.3%), AIns (n=182; 1.2%), KRT5-14 (n=94; <1%), AFib (n=71; <1%), AApoAIV (n=57; <1%), AApoA1 (n=56; <1%), AANF (n=47; <1%), Aβ2M (n=38; <1%), ASem1 (n=34; <1%), AGel (n=29; <1%), TGFB1 (n=29; <1%), ALys (n=15; <1%), AIAPP (n=13; <1%), AApoCII (n=11; <1%), APro (n=8; <1%), AEnf (n=6; <1%), and ACal (n=2; <1%). We developed the first comprehensive organ-by-type map showing the relative frequency of 21 amyloid types in 31 different organs, and the first type-by-organ map showing organ tropism of 18 rare types. Using a modified bioinformatics pipeline, we detected amino acid substitutions in cases of hereditary amyloidosis with 100% specificity.

CONCLUSION

Amyloid typing by proteomics, which effectively recognizes all amyloid types in a single assay, optimally supports the diagnosis and treatment of amyloidosis patients in routine clinical practice.

First Report of Bilateral External Auditory Canal Cochlin Aggregates ("Cochlinomas") with Multifocal Amyloid-Like Deposits, Associated with Sensorineural Hearing Loss and a Novel Genetic Variant in COCH Encoding Cochlin

Pathogenic variants in COCH, encoding cochlin, cause DFNA9 deafness disorder with characteristic histopathologic findings of cochlin deposits in the inner and middle ears. Here, we present the first case of deafness associated with bilateral external auditory canal (EAC) cochlin deposits, previously unreported evidence suggestive of cochlin-derived amyloid formation, and a novel COCH variant. A 54-year-old woman presented with progressive sensorineural hearing loss and bilateral EAC narrowing by subcutaneous thickening. Excision and histologic evaluation of tissue from both EACs showed paucicellular eosinophilic aggregates containing multiple Congo red-positive foci with yellow and green birefringence under crossed polarization light microscopy. Mass spectrometry performed on both the Congo red-positive and Congo red-negative areas identified cochlin as the most abundant protein, as well as a low abundance of universal amyloid signature peptides only in the Congo red-positive areas. Peptides indicative of a canonical amyloid type were not detected. Electron microscopy showed haphazard, branched microfibrils (3-7 nm in diameter) consistent with cochlin, as well as swirling fibrils (10-24 nm in diameter) reminiscent of amyloid fibrils. Cochlin immunohistochemical staining showed positivity throughout the aggregates. Sequencing of the entire COCH gene coding region from the patient's blood revealed a novel variant resulting in a non-conservative amino acid substitution of isoleucine to phenylalanine (c.1621A>T, p.I541F) in the vWFA2 domain at the protein's C-terminus. Our findings reveal a new pathologic manifestation of cochlin, raise the possibility of previously undescribed cochlin-derived amyloid formation, and highlight the importance of thoroughly investigating all aggregative tissue findings in the practice of diagnostic pathology.

Impact of a breast cancer (BC) polygenic risk score (PRS) on the decision to take preventive endocrine therapy (ET): The Genetic Risk Estimate (GENRE) trial

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Background: Despite BC risk reduction of 50-65% by preventive endocrine therapy (ET), very few at-risk women choose to take them. A woman’s perceived BC risk correlates with uptake of ET. A PRS comprised of 77 BC genetic susceptibility loci (Single Nucleotide Polymorphisms (SNP) improves the accuracy of risk prediction for BC. We examined the impact of the addition of individualized PRS BC risk prediction to standard risk calculator estimates on intent to take BC prevention medication. Methods: Eligible women had ≥5% 10 yr BC Tyrer-Cuzick risk (IBIS) or 5 year Gail score ≥3%, with no history of BC or hereditary BC syndrome. Standard BC risk estimates (IBIS or Gail) were incorporated into the counselling on BC preventive ET. A self-reported questionnaire at baseline quantified intention to take ET and explored factors associated with this decision. Blood samples were obtained and genotyped for 77 SNPs, individualized PRS were calculated then incorporated into IBIS and Gail predictions for 5 yr, 10 yr, & lifetime BC risk. At a second visit, PRS risk & prevention recommendations were revisited. Post visit questionnaires assessed change in intent to take ET. Multivariable linear regression was performed to assess impact of baseline variables on change in intent to take medication. Results: From 2016 to 2017, 151 women in Canada & USA were enrolled, median age: 56.1 (range 36-76.4), 35.6% were premenopausal, 98.7% were Caucasian. Median 5yr, 10yr, & lifetime IBIS risk estimates were 3.8% (2.0-11.5), 7.9% (5.0-23.1), and 25.3% (5.5 to 92.2). PRS increased BC risk estimates in 84 (55.6%) and reduced BC risk estimates in 67 (44%) women. After PRS risk counselling, intention to take ET significantly changed (p<0.001): 41.9% of those with increased PRS were more inclined, and 46.7% of women with decreased PRS were less inclined to take ET. On multivariable regression, increase in PRS (p<0.0001) and less concern about ET side effects (p<0.0001) were associated with greater intent to take ET. Conclusions: In high risk women, PRS significantly changed BC risk estimates & intent to take preventive ET. Further assessments of the impact of PRS scores on compliance with ET are warranted. Clinical trial information: NCT02517593.

Identification of aggressive Gardner syndrome phenotype associated with a de novo APC variant, c.4666dup

Gardner syndrome describes a variant phenotype of familial adenomatous polyposis (FAP), primarily characterized by extracolonic lesions including osteomas, dental abnormalities, epidermal cysts, and soft tissue tumors. We describe a 2-yr-old boy presenting with a 2-cm soft tissue mass of the forehead. Pathologic evaluation revealed a nuchal-type/Gardner-associated fibroma. Sequencing of the APC gene revealed a pathologic variant c.4666dupA. Parental sequencing of both blood and buccal tissue supported the de novo occurrence of this pathologic variant. Further imaging revealed a number of additional lesions including a large lumbar paraspinal desmoid, a 1-cm palpable lesion posterior to the left knee, firm lesions on bilateral heels, and multiple subdermal lesions. Colonoscopy was negative. This case illustrates a genetic variant of Gardner syndrome resulting in an aggressive early childhood phenotype and highlights the need for an individualized approach to treatment.

Applying Standard Clinical Chemistry Assay Validation to Droplet Digital PCR Quantitative Liquid Biopsy Testing

BACKGROUND

Droplet digital PCR (ddPCR) is an emerging technology for quantitative cell-free DNA oncology applications. However, assay performance criteria must be established in a standardized manner to harness this potential. We reasoned that standard protocols used in clinical chemistry assay validation should be able to fill this need.

METHODS

We validated KRAS, EGFR, and BRAF quantitative ddPCR assays based on the Clinical Laboratory Improvement Act regulations for laboratory-developed tests in clinical chemistry and the matching Clinical and Laboratory Standards Institute guidelines. This included evaluation of limit of the blank (LOB), limit of detection (LOD), limit of quantification (LOQ), intraassay and interassay imprecision, analytical range, dilution linearity, accuracy (including comparison with orthogonal platforms), reference range study, interference, and stability studies.

RESULTS

For the ddPCR assays, the LOB was 4 mutant copies, LODs were 12 to 22 copies, and LOQs were 35 to 64 copies. The upper limit of the dynamic range was 30000 copies, and dilutions were linear down to the LOQs with good accuracy of spike recovery of Horizon reference material. Method comparisons with next-generation sequencing and an alternative ddPCR platform showed complete qualitative agreement and quantitative concordance, with slopes of 0.73 to 0.97 and R2s of 0.83 to 0.99. No substantial interferences were discovered. Wild-type copy numbers in plasma ranged from 462 to 6169/mL in healthy individuals.

CONCLUSIONS

Standard clinical chemistry assay validation protocols can be applied to quantitative ddPCR assays. This should facilitate comparison of the performance of different assays and allow establishment of minimal significant change thresholds in monitoring applications.

The Power of Proficiency Testing: Unraveling Single-Nucleotide Polymorphism Interference, With Potential Impact on Clinical Testing of Spinocerebellar Ataxia Type 3

CONTEXT.—

The College of American Pathologists proficiency testing program has been instrumental in identifying problems in clinical testing.

OBJECTIVE.—

To describe how this program was used to identify a single-nucleotide polymorphism that affects clinical testing for spinocerebellar ataxia type 3.

DESIGN.—

A proficiency testing sample with discordant results for spinocerebellar ataxia type 3 analysis was further evaluated by targeted Sanger sequencing and genotype polymerase chain reaction using multiple DNA polymerases.

RESULTS.—

Of 28 laboratories responding in the spinocerebellar ataxia type 3 Proficiency Survey, 18 reported an incorrect homozygous result and 10 reported the expected heterozygous result. A heterozygous single-nucleotide polymorphism complementary to the 3' end of a published forward primer was identified in the proficiency testing sample, which may have led to allele dropout. However, this primer was used by only 3 of 18 laboratories (16%) reporting a homozygous result. A new forward primer of identical sequence, except for the 3' end being complementary to the single-nucleotide polymorphism, showed the expected heterozygous pattern. The possibility of DNA polymerase 3'-5' exonuclease activity contributing to allele dropout was investigated by testing 9 additional polymerases with and without exonuclease activity. No clear pattern emerged, but enzymes with and without 3'-5' exonuclease activity yielded both homozygous and expected heterozygous results with the published forward primer.

CONCLUSIONS.—

Proactive systematic primer sequence checking is recommended because single-nucleotide polymorphism interference may result in allele dropout and impact clinical testing. Allele dropout is also influenced by other factors, including DNA polymerase exonuclease activity.

A Patient With Hereditary ATTR and a Novel AGel p.Ala578Pro Amyloidosis

Hereditary amyloidosis represents a group of diseases in which mutant proteins are deposited in various organs leading to their dysfunction. Correct identification of the amyloid-causing protein is critical because this will determine the optimal therapy for the patient. The most common type of hereditary amyloidosis is due to mutant transthyretin (ATTRm) deposition and often presents with heart failure or peripheral neuropathy. We report the first known case of a patient who had amyloidosis both due to a mutant transthyretin (p.Val122Ile) and due to a novel variant in the gelsolin gene (p.Ala578Pro). Both mutant proteins were identified by mass spectrometry analysis of amyloid deposits as well as sequencing of the genes. Molecular dynamic simulations suggest that the gelsolin p.Ala578Pro variant is likely amyloidogenic.

CDKN2A Germline Rare Coding Variants and Risk of Pancreatic Cancer in Minority Populations

Background: Pathogenic germline mutations in the CDKN2A tumor suppressor gene are rare and associated with highly penetrant familial melanoma and pancreatic cancer in non-Hispanic whites (NHW). To date, the prevalence and impact of CDKN2A rare coding variants (RCV) in racial minority groups remain poorly characterized. We examined the role of CDKN2A RCVs on the risk of pancreatic cancer among minority subjects.Methods: We sequenced CDKN2A in 220 African American (AA) pancreatic cancer cases, 900 noncancer AA controls, and 183 Nigerian controls. RCV frequencies were determined for each group and compared with that of 1,537 NHW patients with pancreatic cancer. Odds ratios (OR) and 95% confidence intervals (CI) were calculated for both a case-case comparison of RCV frequencies in AAs versus NHWs, and case-control comparison between AA cases versus noncancer AA controls plus Nigerian controls. Smaller sets of Hispanic and Native American cases and controls also were sequenced.Results: One novel missense RCV and one novel frameshift RCV were found among AA patients: 400G>A and 258_278del. RCV carrier status was associated with increased risk of pancreatic cancer among AA cases (11/220; OR, 3.3; 95% CI, 1.5-7.1; P = 0.004) compared with AA and Nigerian controls (17/1,083). Further, AA cases had higher frequency of RCVs: 5.0% (OR, 13.4; 95% CI, 4.9-36.7; P < 0.001) compared with NHW cases (0.4%).Conclusions: CDKN2A RCVs are more common in AA than in NHW patients with pancreatic cancer and associated with moderately increased pancreatic cancer risk among AAs.Impact: RCVs in CDKN2A are frequent in AAs and are associated with risk for pancreatic cancer. Cancer Epidemiol Biomarkers Prev; 27(11); 1364-70. ©2018 AACR.

DnaJ Heat Shock Protein Family B Member 9 Is a Novel Biomarker for Fibrillary GN

Fibrillary GN (FGN) is a rare primary glomerular disease. Histologic and histochemical features of FGN overlap with those of other glomerular diseases, and no unique histologic biomarkers for diagnosing FGN have been identified. We analyzed the proteomic content of glomeruli in patient biopsy specimens and detected DnaJ heat shock protein family (Hsp40) member B9 (DNAJB9) as the fourth most abundant protein in FGN glomeruli. Compared with amyloidosis glomeruli, FGN glomeruli exhibited a >6-fold overexpression of DNAJB9 protein. Sanger sequencing and protein sequence coverage maps showed that the DNAJB9 protein deposited in FGN glomeruli did not have any major sequence or structural alterations. Notably, we detected DNAJB9 in all patients with FGN but not in healthy glomeruli or in 19 types of non-FGN glomerular diseases. We also observed the codeposition of DNAJB9 and Ig-γ Overall, these findings indicate that DNAJB9 is an FGN marker with 100% sensitivity and 100% specificity. The magnitude and specificity of DNAJB9 overabundance in FGN also suggests that this protein has a role in FGN pathogenesis. With this evidence, we propose that DNAJB9 is a strong biomarker for rapid diagnosis of FGN in renal biopsy specimens.

Hereditary Lysozyme Amyloidosis Variant p.Leu102Ser Associates with Unique Phenotype

Lysozyme amyloidosis (ALys) is a rare form of hereditary amyloidosis that typically manifests with renal impairment, gastrointestinal (GI) symptoms, and sicca syndrome, whereas cardiac involvement is exceedingly rare and neuropathy has not been reported. Here, we describe a 40-year-old man with renal impairment, cardiac and GI symptoms, and peripheral neuropathy. Renal biopsy specimen analysis revealed amyloidosis with extensive involvement of glomeruli, vessels, and medulla. Amyloid was also detected in the GI tract. Echocardiographic and electrocardiographic findings were consistent with cardiac involvement. Proteomic analysis of Congo red-positive renal and GI amyloid deposits detected abundant lysozyme C protein. DNA sequencing of the lysozyme gene in the patient and his mother detected a heterozygous c.305T>C alteration in exon 3, which causes a leucine to serine substitution at codon 102 (Human Genome Variation Society nomenclature: p.Leu102Ser; legacy designation: L84S). We also detected the mutant peptide in the proband's renal and GI amyloid deposits. PolyPhen analysis predicted that the mutation damages the encoded protein. Molecular dynamics simulations suggested that the pathogenesis of ALys p.Leu102Ser is mediated by shifting the position of the central β-hairpin coordinated with an antiparallel motion of the C-terminal helix, which may alter the native-state structural ensemble of the molecule, leading to aggregation-prone intermediates.

Mitochondrial DNA sequence data reveals association of haplogroup U with psychosis in bipolar disorder

Converging genetic, postmortem gene-expression, cellular, and neuroimaging data implicate mitochondrial dysfunction in bipolar disorder. This study was conducted to investigate whether mitochondrial DNA (mtDNA) haplogroups and single nucleotide variants (SNVs) are associated with sub-phenotypes of bipolar disorder. MtDNA from 224 patients with Bipolar I disorder (BPI) was sequenced, and association of sequence variations with 3 sub-phenotypes (psychosis, rapid cycling, and adolescent illness onset) was evaluated. Gene-level tests were performed to evaluate overall burden of minor alleles for each phenotype. The haplogroup U was associated with a higher risk of psychosis. Secondary analyses of SNVs provided nominal evidence for association of psychosis with variants in the tRNA, ND4 and ND5 genes. The association of psychosis with ND4 (gene that encodes NADH dehydrogenase 4) was further supported by gene-level analysis. Preliminary analysis of mtDNA sequence data suggests a higher risk of psychosis with the U haplogroup and variation in the ND4 gene implicated in electron transport chain energy regulation. Further investigation of the functional consequences of this mtDNA variation is encouraged.

Novel Type of Renal Amyloidosis Derived from Apolipoprotein-CII

Amyloidosis is characterized by extracellular deposition of misfolded proteins as insoluble fibrils. Most renal amyloidosis cases are Ig light chain, AA, or leukocyte chemotactic factor 2 amyloidosis, but rare hereditary forms can also involve the kidneys. Here, we describe the case of a 61-year-old woman who presented with nephrotic syndrome and renal impairment. Examination of the renal biopsy specimen revealed amyloidosis with predominant involvement of glomeruli and medullary interstitium. Proteomic analysis of Congo red-positive deposits detected large amounts of the Apo-CII protein. DNA sequencing of the APOC2 gene in the patient and one of her children detected a heterozygous c.206A→T transition, causing an E69V missense mutation. We also detected the mutant peptide in the proband's renal amyloid deposits. Using proteomics, we identified seven additional elderly patients with Apo-CII-rich amyloid deposits, all of whom had kidney involvement and histologically exhibited nodular glomerular involvement. Although prior in vitro studies have shown that Apo-CII can form amyloid fibrils and that certain mutations in this protein promote amyloid fibrillogenesis, there are no reports of this type of amyloidosis in humans. We propose that this study reveals a new form of hereditary amyloidosis (AApoCII) that is derived from the Apo-CII protein and appears to manifest in the elderly and preferentially affect the kidneys.

Trinucleotide Repeat Expansion in the TCF4 Gene in Fuchs' Endothelial Corneal Dystrophy in Japanese

PURPOSE

The purpose of this study was to evaluate the association between the intronic expansion of a trinucleotide repeat (TNR) in the TCF4 gene and Fuchs' endothelial corneal dystrophy (FECD) in a Japanese population.

METHODS

Forty-seven Japanese FECD patients and 96 age-matched controls were recruited. FECD patients and controls were examined by slit-lamp and noncontact specular microscopy. The repeat length was determined by direct sequencing and short tandem repeat assay of PCR-amplified DNA and Southern blotting of unamplified DNA.

RESULTS

A TNR expansion, defined as >50 CTG repeats in the TCF4 gene was identified in 12 of 47 FECD cases (26%) and 0 of 96 controls (0%; P < 0.001). Sensitivity and specificity in this study were 26% and 100%, respectively. The clinical characteristics of FECD patients with TNR expansion were not distinct from those without TNR expansion.

CONCLUSIONS

These findings show for the first time in a Japanese population the association of the TNR expansion in TCF4 with FECD. In contrast to Caucasian cohorts in whom the TNR expansion is present in most patients with FECD, a CTG expansion is present in a minority of Japanese subjects, indicating other genetic variants as common causes of phenotypically identical disease in this population.

Whole-Exome Sequencing of 10 Scientists: Evaluation of the Process and Outcomes

OBJECTIVE

To understand motivations, educational needs, and concerns of individuals contemplating whole-exome sequencing (WES) and determine what amount of genetic information might be obtained by sequencing a generally healthy cohort so as to more effectively counsel future patients.

PATIENTS AND METHODS

From 2012 to 2014, 40 medically educated, generally healthy scientists at Mayo Clinic were invited to have WES conducted on a research basis; 26 agreed to be in a drawing from which 10 participants were selected. The study involved pre- and posttest genetic counseling and completion of 4 surveys related to the experience and outcomes. Whole-exome sequencing was conducted on DNA from blood from each person.

RESULTS

Most variants (76,305 per person; range, 74,505-77,387) were known benign allelic variants, variants in genes of unknown function, or variants of uncertain significance in genes of known function. The results of suspected pathogenic/pathogenic variants in Mendelian disorders and pharmacogenomic variants were disclosed. The mean number of suspected pathogenic/pathogenic variants was 2.2 per person (range, 1-4). Four pharmacogenomic genes were included for reporting; variants were found in 9 of 10 participants.

CONCLUSION

This study provides data that may be useful in establishing reality-based patient expectations, outlines specific points to cover during counseling, and increases confidence in the feasibility of providing adequate preparation and counseling for WES in generally healthy individuals.

Targeting the hypoxia pathway to treat pancreatic cancer

The correlation between hypoxia and pancreatic cancer has long been discussed. Hao’s research team made many efforts on revealing the oncogenic function of hypoxic inducible factor-1 (HIF-1) in pancreatic cancer progression and development in recent years. Based on their research, they linked micro-environmental regulation of pancreatic cancer and its clinical significance. Hao’s research team suggests it is a promising approach to target HIF-1 for the management of pancreatic cancer progression and invasion.

Biochemical and computational analyses of two phenotypically related GALT mutations (S222N and S135L) that lead to atypical galactosemia

Galactosemia is a metabolic disorder caused by mutations in the GALT gene [1,2]. We encountered a patient heterozygous for a known pathogenic H132Q mutation and a novel S222N variant of unknown significance [3]. Reminiscent of patients with the S135L mutation, our patient had loss of GALT enzyme activity in erythrocytes but a very mild clinical phenotype [3–8]. We performed splicing experiments and computational structural analyses to investigate the role of the novel S222N variant. Alamut software data predicted loss of splicing enhancers for the S222N and S135L mutations [9,10]. A cDNA library was generated from our patient׳s RNA to investigate for splicing errors, but no change in transcript length was seen [3]. In silico structural analysis was performed to investigate enzyme stability and attempt to understand the mechanism of the atypical galactosemia phenotype. Stability results are publicly available in the GALT Protein Database 2.0 [11–14]. Animations were created to give the reader a dynamic view of the enzyme structure and mutation locations. Protein database files and python scripts are included for further investigation.

Compound heterozygosity with a novel S222N GALT mutation leads to atypical galactosemia with loss of GALT activity in erythrocytes but little evidence of clinical disease

Galactosemia is an inborn error of galactose metabolism caused by mutations in the GALT gene. Though early detection and galactose restriction prevent severe liver disease, affected individuals have persistently elevated biomarkers and often neuro-developmental symptoms. We present a teenage compound heterozygote for a known pathogenic mutation (H132Q) and a novel variant of unknown significance (S222N), with nearly absent erythrocyte GALT enzyme activity but normal biomarkers and only mild anxiety despite diet non-adherence. This case is similar to a previously reported S135L mutation. In this report we investigate the novel S222N variant and critically evaluate a clinically puzzling case.

Neurodevelopmental disabilities in children with intermediate and premutation range fragile X cytosine-guanine-guanine expansions

To determine the range of neurodevelopmental diagnoses associated with intermediate (45-54 repeats) and premutation (55-200 repeats) range cytosine-guanine-guanine fragile X expansions, the medical records of children with intermediate or premutation range expansions were retrospectively reviewed, and all neurodevelopmental diagnoses were abstracted. Twenty-nine children (9 female, 20 male; age, 13 months to 17 years) with intermediate (n = 25) or premutation (n = 4) range expansions were identified with neurodevelopmental diagnoses, including global developmental delay/intellectual disability (n = 15), language and learning disorders (n = 9), attention-deficit hyperactivity disorder (n = 5), epilepsy (n = 5), and motor disorders (n = 12), including 2 boys younger than 4 years of age with tremor and ataxia. Thus, children with intermediate or premutation range fragile X cytosine-guanine-guanine expansions may be more susceptible than children without such expansions to other processes, both genetic and environmental, that contribute to neurodevelopmental disability.

Homozygosity for the V122I mutation in transthyretin is associated with earlier onset of cardiac amyloidosis in the African American population in the seventh decade of life

Individuals heterozygous for the V122I mutation in transthyretin (TTR) tend to develop cardiac amyloidosis, often after the seventh decade of life. Although homozygotes have been reported, these have typically been single case reports. We report a cohort of 13 V122I homozygotes. TTR gene sequencing results from the Mayo Clinic Molecular Genetics Laboratory between September 2004 and January 2013 were reviewed; 177 heterozygotes and 13 homozygotes for the V122I alteration were identified. Detailed clinical history was available for the 24 heterozygotes seen at Mayo Clinic. We compared age at onset of disease for this group to homozygotes, both alone and pooled with the 11 homozygotes from the literature. Individuals with homozygous V122I manifested symptoms a mean of 10 years earlier than heterozygotes (63.8 ± 5.7 versus 72 ± 8.1 yrs, P = 0.0002). Further, males were significantly overrepresented in both heterozygous and homozygous individuals. There was a trend for an even higher male bias in the homozygous group. All 24 homozygotes were African American, whereas four of the heterozygotes were reported as white. Two novel V122I compound heterozygotes were also identified, with clinical presentation in the late fifth or early sixth decade of life. This study is the largest homozygous V122I cohort reported and demonstrates association with earlier age at onset. It also highlights the uncertain penetrance, particularly with respect to sex.

Systemic transthyretin amyloidosis in a patient with bent spine syndrome

Wild-type and mutant transthyretin (TTR) are implicated in systemic amyloidosis (ATTR). Myopathy is a rare complication of ATTR amyloidosis, however no patient with bent spine syndrome secondary to ATTR amyloidosis has been reported so far. We present the first case of bent spine syndrome in a patient with wild-type ATTR amyloidosis who also had concomitant Alzheimer's disease.

Multisite validation study to determine performance characteristics of a 92-gene molecular cancer classifier

PURPOSE

Accurate tumor classification is essential for cancer management as patient outcomes improve with use of site- and subtype-specific therapies. Current clinicopathologic evaluation is varied in approach, yet standardized diagnoses are critical for determining therapy. While gene expression-based cancer classifiers may potentially meet this need, imperative to determining their application to patient care is validation in rigorously designed studies. Here, we examined the performance of a 92-gene molecular classifier in a large multi-institution cohort.

EXPERIMENTAL DESIGN

Case selection incorporated specimens from more than 50 subtypes, including a range of tumor grades, metastatic and primary tumors, and limited tissue samples. Formalin-fixed, paraffin-embedded tumors passed pathologist-adjudicated review between three institutions. Tumor classification using a 92-gene quantitative reverse transcriptase polymerase chain reaction (RT-PCR) assay was conducted on blinded tumor sections from 790 cases and compared with adjudicated diagnoses.

RESULTS

The 92-gene assay showed overall sensitivities of 87% for tumor type [95% confidence interval (CI), 84-89] and 82% for subtype (95% CI, 79-85). Analyses of metastatic tumors, high-grade tumors, or cases with limited tissue showed no decrease in comparative performance (P = 0.16, 0.58, and 0.16). High specificity (96%-100%) was showed for ruling in a primary tumor in organs commonly harboring metastases. The assay incorrectly excluded the adjudicated diagnosis in 5% of cases.

CONCLUSIONS

The 92-gene assay showed strong performance for accurate molecular classification of a diverse set of tumor histologies. Results support potential use of the assay as a standardized molecular adjunct to routine clinicopathologic evaluation for tumor classification and primary site diagnosis.

Multisite validation of a 92-gene molecular classifier: Diagnostic accuracy and clinical utility in metastatic cancer

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Background: Accurate tumor classification is increasingly critical to individualized care as patient outcomes improve with use of targeted cancer therapies and predictive biomarkers. In metastatic cancers of uncertain or unknown origin, identification of a primary site remains equivocal in a significant number of cases. Gene expression signatures may improve accuracy and specificity of tumor classification, however, large-scale, blinded validation studies that demonstrate stable performance in metastatic and poorly differentiated cases are currently lacking. Methods: Seven hundred and ninety cases (51% female, 44% metastatic, 63% grade 2 and 3, 14% limited tissue specimens) representing 28 tumor types and 50 subtypes were processed and adjudicated between Mayo Clinic, UCLA and Massachusetts General Hospital. Blinded FFPE tumor sections were submitted and tested using a 92-gene RT-PCR assay (CancerTYPE ID, bioTheranostics Inc.). Molecular predictions were evaluated for concordance with the reference diagnosis; diagnostic accuracy between clinical subsets was compared. Results: The 92-gene assay demonstrated overall sensitivities of 87% for tumor classification and 82% for subtyping. Forty-seven (5.9%) cases were considered unclassifiable. Comparative analysis of performance between metastatic (n=329) and primary (n=414) tumors showed no statistically significant difference in accuracy (85% vs 88%, p=0.16). Similarly, no significant decreases in performance were observed across histological grades (p=0.58) and when comparing limited tissue to excisional biopsy specimens (p=0.16). Strong precision was demonstrated for accurate identification of a primary tumor in tissues biopsied from common metastatic sites, reported as positive predictive values of 100% for lung, brain and peritoneum, 92% for ovary and 80% for liver. Conclusions: Results from this multisite, blinded study validate the diagnostic accuracy of the 92-gene assay for classifying a diverse set of tumors, and support its clinical utility in the diagnosis of metastatic tumors to determine tissue of origin, and in the differential diagnosis of metastatic vs new primary disease.

Isocitrate dehydrogenase 1 and 2 mutations in cholangiocarcinoma

Somatic mutations in isocitrate dehydrogenase 1 and 2 genes are common in gliomas and help stratify patients with brain cancer into histologic and molecular subtypes. However, these mutations are considered rare in other solid tumors. The aims of this study were to determine the frequency of isocitrate dehydrogenase 1 and 2 mutations in cholangiocarcinoma and to assess histopathologic differences between specimens with and without an isocitrate dehydrogenase mutation. We sequenced 94 formalin-fixed, paraffin-embedded cholangiocarcinoma (67 intrahepatic and 27 extrahepatic) assessing for isocitrate dehydrogenase 1 (codon 132) and isocitrate dehydrogenase 2 (codons 140 and 172) mutations. Multiple histopathologic characteristics were also evaluated and compared with isocitrate dehydrogenase 1/2 mutation status. Of the 94 evaluated specimens, 21 (22%) had a mutation including 14 isocitrate dehydrogenase 1 and 7 isocitrate dehydrogenase 2 mutations. Isocitrate dehydrogenase mutations were more frequently observed in intrahepatic cholangiocarcinoma than in extrahepatic cholangiocarcinoma (28% versus 7%, respectively; P = .030). The 14 isocitrate dehydrogenase 1 mutations were R132C (n = 9), R132S (n = 2), R132G (n = 2), and R132L (n = 1). The 7 isocitrate dehydrogenase 2 mutations were R172K (n = 5), R172M (n = 1), and R172G (n = 1). Isocitrate dehydrogenase mutations were more frequently observed in tumors with clear cell change (P < .001) and poorly differentiated histology (P = .012). The results of this study show for the first time that isocitrate dehydrogenase 1 and 2 genes are mutated in cholangiocarcinoma. The results of this study are encouraging because it identifies a new potential target for genotype-directed therapeutic trials and may represent a potential biomarker for earlier detection of cholangiocarcinoma in a subset of cases.

The germline MLH1 K618A variant and susceptibility to Lynch syndrome-associated tumors

Missense variants discovered during sequencing of cancer susceptibility genes can be problematic for clinical interpretation. MLH1 K618A, which results from a 2-bp alteration (AAG→GCG) leading to a substitution of lysine to alanine in codon 618, has variously been interpreted as a pathogenic mutation, a variant of unknown significance, and a benign polymorphism. We evaluated the role of MLH1 K618A in predisposition to cancer by genotyping 1512 control subjects to assess its frequency in the general population. We also reviewed the literature concerning MLH1 K618A in families with colorectal cancer. The measured allele frequency of the K618A variant was 0.40%, which is remarkably close to the 0.44% summarized from 2491 control subjects in the literature. K618A was over-represented in families with suspected Lynch syndrome. In 1366 families, the allele frequency was 0.88% (OR = 2.1, 95% CI = 1.3 to 3.5; P = 0.006). In studies of sporadic cancers of the type associated with Lynch syndrome, K618A was over-represented in 1742 cases (allele frequency of 0.83) (OR = 2.0, 95% CI = 1.2 to 3.2; P = 0.008). We conclude that MLH1 K618A is not a fully penetrant Lynch syndrome mutation, although it is not without effect, appearing to increase the risk of Lynch syndrome-associated tumors approximately twofold. Our systematic assessment approach may be useful for variants in other genes.

Development and clinical implementation of a combination deletion PCR and multiplex ligation-dependent probe amplification assay for detecting deletions involving the human α-globin gene cluster

The α-thalassemias are a group of hereditary disorders caused by reduced synthesis of the α-chain of hemoglobin. We have developed and tested an α-thalassemia assay that uses both multiplex ligation-dependent probe amplification (MLPA) with Luminex-based detection and deletion PCR technologies. The MLPA assay consisted of 20 probes, 15 of which hybridized to the α-globin gene cluster and 5 that served as control probes. A PCR assay was developed to confirm the presence of heterozygous/homozygous 3.7-kb and 4.2-kb deletions. MLPA and PCR results were compared to Southern blot (SB) results from 758 and 133 specimens, respectively. Lastly, MLPA and PCR results were reviewed and summarized from 5386 clinically tested specimens. SB and MLPA results were concordant in 678/687 (99%) specimens. PCR detected all deletions detected by SB with no false positives. No deletions or duplications were identified in 2630 (49%) clinically tested specimens. Extra α-globin copies were identified in 76 patients. A deletion of one or two α-globin genes was identified in 1251 (23%) and 1349 (25%) specimens, respectively, including 15 different genotypes. A deletion of three (hemoglobin H) and four α-globin genes (Hb Bart's) was observed in 65 or 3 specimens, respectively. Six patients had a deletion within the α-globin regulatory region MCS-R2. Thus, MLPA plus deletion PCR identify multiple α-globin gene deletions/duplications in patients being tested for α-thalassemia.

Hereditary hemochromatosis: laboratory evaluation

The condition of hereditary hemochromatosis (HH) is caused by gene-dependent protein abnormalities involved in iron absorption, storage, or modulation of iron; these abnormalities result in iron overload. The clinical laboratory plays a significant role in case finding, diagnostic validation, and monitoring HH therapy. Elevated serum iron, transferrin saturation, and ferritin suggest HH, but results can also indicate other forms of hepatocyte injury such as alcoholic or viral hepatitis, or other inflammatory disorders involving the liver. In the context of elevated serum iron, transferrin saturation, and ferritin, and after ruling out secondary causes of iron overload, HFE gene evaluation is the preferred test to confirm the diagnosis of HH. However, 5% to 15% of patients with phenotypic HH do not have HFE gene mutations. In these cases, MRI evaluation or liver biopsy with iron quantification is indicated. The clinical role of hepcidin, the iron modulating protein, is undetermined at this time. Because hepcidin also plays a key role in antimicrobial and inflammatory activities, interpretation of hepcidin serum or urine concentration will require thorough understanding of its complex role in iron regulation.

Detailed molecular fingerprinting of four new anaplastic thyroid carcinoma cell lines and their use for verification of RhoB as a molecular therapeutic target

CONTEXT

Anaplastic thyroid carcinoma (ATC) is a highly aggressive carcinoma in need of therapeutic options. One critical component of drug discovery is the availability of well-characterized cell lines for identification of molecular mechanisms related to tumor biology and drug responsiveness. Up to 42% of human thyroid cancer cell lines are redundant or not of correct tissue origin, and a comprehensive analysis is currently nonexistent. Mechanistically, RhoB has been identified as a novel molecular target for ATC therapy.

OBJECTIVE

The aim was to develop four ATC cell lines detailing genetic, molecular, and phenotypic characteristics and to test five classes of drugs on the cell lines to determine whether they inhibited cell proliferation in a RhoB-dependent fashion.

DESIGN

Four cell lines were derived from ATC tumors. Short tandem DNA repeat and mutational status of the originating tumors and cell lines were performed along with molecular and phenotypic characterizations. Compounds were tested for growth inhibition and ability to up-regulate RhoB.

RESULTS

Cell line authenticity was confirmed by DNA short tandem repeat analysis. Each proved unique regarding expression of thyroid markers, oncogene status, amplified and deleted genes, and proliferative growth rates. FTI-277, GGTI-286, lovastatin, romidepsin, and UCN-01 up-regulated RhoB and inhibited cell proliferation in a dose-responsive fashion with only romidepsin and FTI-277 being RhoB dependent.

CONCLUSIONS

Molecular descriptions of thyroid lines were matched to the originating tumors, setting a new standard for cell line characterization. Furthermore, suppressed RhoB is implicated as a molecular target for therapy against ATC because five classes of drugs up-regulate RhoB and inhibit growth dose-responsively.

The suitability of matrix assisted laser desorption/ionization time of flight mass spectrometry in a laboratory developed test using cystic fibrosis carrier screening as a model

We designed a laboratory developed test (LDT) by using an open platform for mutation/polymorphism detection. Using a 108-member (mutation plus variant) cystic fibrosis carrier screening panel as a model, we completed the last phase of LDT validation by using matrix-assisted laser desorption/ionization time of flight mass spectrometry. Panel customization was accomplished via specific amplification primer and extension probe design. Amplified genomic DNA was subjected to allele specific, single base extension endpoint analysis by mass spectrometry for inspection of the cystic fibrosis transmembrane regulator gene (NM_000492.3). The panel of mutations and variants was tested against 386 blinded samples supplied by "authority" laboratories highly experienced in cystic fibrosis transmembrane regulator genotyping; >98% concordance was observed. All discrepant and discordant results were resolved satisfactorily. Taken together, these results describe the concluding portion of the LDT validation process and the use of mass spectrometry to detect a large number of complex reactions within a single run as well as its suitability as a platform appropriate for interrogation of scores to hundreds of targets.

Allelic diversity in MCAD deficiency: the biochemical classification of 54 variants identified during 5 years of ACADM sequencing

Medium-chain acyl-coA dehydrogenase (MCAD) deficiency is a commonly detected fatty acid oxidation disorder and its diagnosis relies on both biochemical and molecular analyses. Over a 5-year period, sequencing all 12 exons of the MCAD gene (ACADM) in our laboratory revealed a total of 54 variants in 549 subjects analyzed. As most molecular ACADM testing is referred for the follow-up of an abnormal newborn screening result obtained from an asymptomatic newborn, the identification of a novel DNA variant, or "variant of unknown significance (VUS)," presents clinicians with a dilemma. Frequently, the results of molecular analyses are correlated to biochemical findings, such as the concentration of octanoylcarnitine (C8) in plasma and the excretion of hexanoylglycine (HG) in urine. Here, we describe the classification of genotypes harboring at least one VUS through the comparison of C8 and HG values measured in individuals who are carriers of, or affected with, MCAD deficiency on the basis of the following genotypes: c.985A>G/wildtype, c.199T>C/c.985A>G and c.985A>G/c.985A>G. Our findings emphasize the importance of obtaining both plasma and urine when following up positive newborn screening results and may influence the way physicians counsel their asymptomatic patients about MCAD deficiency after genetic analysis.

Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations and risk for pancreatic adenocarcinoma

BACKGROUND

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are common in white persons and are associated with pancreatic disease. The purpose of this case-control study was to determine whether CFTR mutations confer a higher risk of pancreatic cancer.

METHODS

In a case-control study, the authors compared the rates of 39 common cystic fibrosis-associated CFTR mutations between 949 white patients with pancreatic adenocarcinoma and 13,340 white controls from a clinical laboratory database for prenatal testing for CFTR mutations. The main outcome measure was the CFTR mutation frequency in patients and controls.

RESULTS

Overall, 50 (5.3%) of 949 patients with pancreatic cancer carried a common CFTR mutation versus 510 (3.8%) of 13,340 controls (odds ratio [OR], 1.40; 95% confidence interval [CI], 1.04-1.89; P = .027). Among patients who were younger when their disease was diagnosed (<60 years), the carrier frequency was higher than in controls (OR, 1.82; 95% CI, 1.14-2.94; P = .011). In patient-only analyses, the presence of a mutation was associated with younger age (median 62 vs 67 years; P = .034). In subgroups, the difference was seen only among ever-smokers (60 vs 65 years, P = .028). Subsequent sequencing analysis of the CFTR gene detected 8 (16%) compound heterozygotes among the 50 patients initially detected to have 1 mutation.

CONCLUSIONS

Carrying a disease-associated mutation in CFTR is associated with a modest increase in risk for pancreatic cancer. Those affected appear to be diagnosed at a younger age, especially among smokers. Clinical evidence of antecedent pancreatitis was uncommon among both carriers and noncarriers of CFTR mutations.

Real time PCR detection of the PI*Z and PI*S mutations associated with alpha-1 antitrypsin deficiency

Alpha-1 antitrypsin (A1AT or AAT) is a serine protease inhibitor (PI) which, when present at low levels, can cause chronic obstructive pulmonary disease (COPD) and liver disease in both children and adults. Several mutations within the SERPINA1 gene have been found to cause this deficiency. The most common variants are PI*Z and PI*S, each caused by a single nucleotide polymorphism (SNP). We describe a real time polymerase chain reaction (PCR) assay for the rapid genotyping of these polymorphisms. DNA was extracted from fourteen EDTA-anticoagulated whole blood samples using the Qiagen EZ1 blood extraction kit. SNP genotyping was performed using primer/probe sets purchased from Applied Biosystems. These were evaluated for performance and assay conditions on the Applied Biosystems 7500 FAST System. The genotypes of these samples were compared with their phenotype results from isoelectric focusing assays, which were performed by an independent reference laboratory. In addition, twenty samples that were previously genotyped at another laboratory were obtained for accuracy studies. Thirty-four samples were tested; five genotypes were represented and the assay was able to discriminate these successfully. Only one genotype could not be correlated with its phenotype result, as the phenotype was reported as an "unidentified allele". All other genotyping results were concordant with previously determined genotypes and phenotypes. We describe a rapid real time PCR assay that is suitable for clinical use in genotyping AAT alleles and which can be used as the initial step in A1AT testing algorithms.

Quintuple α-Globin Gene: A Novel Allele in a Sudanese Man

Multiple alpha-globin repeats have previously been discovered in humans and other mammals. A quintuple alpha-globin gene (alphaalpha/alphaalphaalphaalphaalpha) was found in a Sudanese male undergoing evaluation for microcytosis.

Development of genomic reference materials for cystic fibrosis genetic testing

The number of different laboratories that perform genetic testing for cystic fibrosis is increasing. However, there are a limited number of quality control and other reference materials available, none of which cover all of the alleles included in commercially available reagents or platforms. The alleles in many publicly available cell lines that could serve as reference materials have neither been confirmed nor characterized. The Centers for Disease Control and Prevention-based Genetic Testing Reference Material Coordination Program, in collaboration with members of the genetic testing community as well as Coriell Cell Repositories, have characterized an extended panel of publicly available genomic DNA samples that could serve as reference materials for cystic fibrosis testing. Six cell lines [containing the following mutations: E60X (c.178G>T), 444delA (c.312delA), G178R (c.532G>C), 1812-1G>A (c.1680-1G>A), P574H (c.1721C>A), Y1092X (c.3277C>A), and M1101K (c.3302T>A)] were selected from those existing at Coriell, and seven [containing the following mutations: R75X (c.223C>T), R347H (c.1040G>A), 3876delA (c.3744delA), S549R (c.1646A>C), S549N (c.1647G>A), 3905insT (c.3773_3774insT), and I507V (c.1519A>G)] were created. The alleles in these materials were confirmed by testing in six different volunteer laboratories. These genomic DNA reference materials will be useful for quality assurance, proficiency testing, test development, and research and should help to assure the accuracy of cystic fibrosis genetic testing in the future. The reference materials described in this study are all currently available from Coriell Cell Repositories.

LOC387715/HTRA1 and complement factor H variants in patients with age-related macular degeneration seen at the mayo clinic

PURPOSE

To confirm association of the complement factor H allelic variant (CFH Y402H) and the LOC387715/HTRA1 (LOC387715 A69S) risk alleles with age-related macular degeneration (AMD).

STUDY POPULATION

Study of 89 Caucasian patients with neovascular (exudative) AMD and 232 Caucasian controls.

METHODS

The Y402H variant of CFH gene and A69S variant of LOC387715/HTRA1 gene locus were examined.

RESULTS

For CFH, the odds ratio for the homozygous variant was 4.97 (CI 2.52 to 9.79). For LOC387715/HTRA1 the odds ratio for the homozygous risk variant was 7.75 (CI 3.46 to 17.35). The odds ratio for heterozygous carriers was 3.35 (CI 1.91 to 5.90).

Conversion Technology for the separation of maternal and paternal copies of any autosomal chromosome in somatic cell hybrids

Conversion Technology (CT) is a streamlined version of somatic cell hybrid preparation that was developed to be amenable for use as a mutation detection method and as a diagnostic tool for individual patients. It is also a powerful research tool. There are two broad categories of potential applications for CT: research applications in gene mapping and identification, and clinical applications in the detection of disease-causing mutations in individual patients. CT may emerge as the gold standard for both mutation detection and haplotyping. It will likely prove valuable in mutation detection due to its ability to detect mutations that are not amenable to detection by sequencing (e.g., deep intron or promoter mutations). It will likely prove valuable in gene identification projects because genotyping of haploid chromosomes yields unequivocal haplotypes.

Consensus characterization of 16 FMR1 reference materials: a consortium study

Fragile X syndrome, which is caused by expansion of a (CGG)(n) repeat in the FMR1 gene, occurs in approximately 1:3500 males and causes mental retardation/behavioral problems. Smaller (CGG)(n) repeat expansions in FMR1, premutations, are associated with premature ovarian failure and fragile X-associated tremor/ataxia syndrome. An FMR1-sizing assay is technically challenging because of high GC content of the (CGG)(n) repeat, the size limitations of conventional PCR, and a lack of reference materials available for test development/validation and routine quality control. The Centers for Disease Control and Prevention and the Association for Molecular Pathology, together with the genetic testing community, have addressed the need for characterized fragile X mutation reference materials by developing characterized DNA samples from 16 cell lines with repeat lengths representing important phenotypic classes and diagnostic cutoffs. The alleles in these materials were characterized by consensus analysis in nine clinical laboratories. The information generated from this study is available on the Centers for Disease Control and Prevention and Coriell Cell Repositories websites. DNA purified from these cell lines is available to the genetics community through the Coriell Cell Repositories. The public availability of these reference materials should help support accurate clinical fragile X syndrome testing.

Comparison of three methods for genotyping the UGT1A1 (TA)n repeat polymorphism

OBJECTIVES

The UGT1A1 promoter contains a (TA)n repeat polymorphism. The 7 repeat allele is associated with decreased enzyme activity and patients homozygous for this allele treated with irinotecan may experience life-threatening toxicity. Here, we have compared three methods [DNA sequencing, fragment analysis, and the Invader assay (Third Wave Technologies)] for genotyping this polymorphism.

RESULTS

All of the DNA samples (n=119) had concordant genotype calls between the sequencing and size-based methods. The Invader method was also concordant if the genotypes were 6/6, 6/7, or 7/7. Both the size-based method and the Invader method had straightforward data analysis, while interpretation of the sequencing results was occasionally more challenging. The Invader method required more concentrated DNA for analysis, was more expensive, and had a limited genotyping spectrum.

CONCLUSION

All three methods were valuable for genotyping the UGT1A1 (TA)n repeat, with the sequencing and size-based assays having the fewest drawbacks.

RET proto-oncogene genotyping using unlabeled probes, the masking technique, and amplicon high-resolution melting analysis

Single bp mutations in the RET proto-oncogene can cause multiple endocrine neoplasia type 2 syndromes. The conventional approach for genotyping RET mutations is sequencing the exons. A closed-tube RET genotyping assay using a saturating DNA dye, unlabeled probes, and amplicon high-resolution melting analysis was developed. The method required two sequential polymerase chain reaction stages, a primary and secondary assay. The primary assay analyzed RET exons 10, 11, 13, 14, and 16 with a total of seven reactions using eight unlabeled probes. The primary assay genotyped wild-type exons, a common exon 13 polymorphism, and an exon 16 mutation, whereas other RET sequence variation was detected. The primary unlabeled probe data limited the possible genotypes for the detected RET sequence variation, which permitted genotyping in a secondary assay with only two to five reactions. Six probes were designed with the masking technique and masked selected sequence variations to allow unambiguous analysis of other mutations elsewhere under the probe. After this two-stage RET genotyping assay, less than 0.2% of exons tested would require sequencing for genotype. A blinded study generated from five wild type and 29 available RET sequence variation samples was 100% concordant with sequencing. Amplicon high-resolution melting analysis with unlabeled probes and the masking technique is a fast, accurate method for genotyping the >50 RET sequence variations.

Homozygous transthyretin mutation in an African American Male

Cardiac amyloidosis of transthyretin type in the elderly may be senile or familial. The senile form is not typically associated with specific genetic changes. However, the familial form is and also occurs more frequently in African Americans than in the general population. One transthyretin mutation, V122I, is common in the African-American population, has a carrier frequency of 4%, and has marked cardiac specificity. Symptoms generally develop in the eighth and ninth decades. Here, we report the case of a 60-year-old African-American man who had a 2-year history of dyspnea and diffuse left ventricular wall thickening. Endomyocardial biopsy showed interstitial deposits of amorphous material confirmed as amyloid by Congo red staining and electron microscopy. Mass spectrometry showed a shift in protein mass of 14 d, indicative of transthyretin and confirming the production of abnormal protein. Bidirectional whole gene sequencing showed a homozygous mutation leading to a valine 122 isoleucine substitution (V122I). The 14-d mass shift observed using mass spectrometry is consistent with the V122I mutation. Homozygosity for the V122I mutation may be associated with earlier onset of cardiac disease. Transthyretin analysis should be considered for older African Americans with amyloid heart disease of transthyretin type.