The role of genetic testing in diagnosis and care of inherited cardiac conditions in a specialised multidisciplinary clinic

BACKGROUND

The diagnostic yield of genetic testing for inherited cardiac diseases is up to 40% and is primarily indicated for screening of at-risk relatives. Here, we evaluate the role of genomics in diagnosis and management among consecutive individuals attending a specialised clinic and identify those with the highest likelihood of having a monogenic disease.

METHODS

A retrospective audit of 1697 consecutive, unrelated probands referred to a specialised, multidisciplinary clinic between 2002 and 2020 was performed. A concordant clinical and genetic diagnosis was considered solved. Cases were classified as likely monogenic based on a score comprising a positive family history, young age at onset, and severe phenotype, whereas low-scoring cases were considered to have a likely complex aetiology. The impact of a genetic diagnosis was evaluated.

RESULTS

A total of 888 probands fulfilled the inclusion criteria, and genetic testing identified likely pathogenic or pathogenic (LP/P) variants in 330 individuals (37%) and suspicious variants of uncertain significance (VUS) in 73 (8%). Research-focused efforts identified 46 (5%) variants, missed by conventional genetic testing. Where a variant was identified, this changed or clarified the final diagnosis in a clinically useful way for 51 (13%). The yield of suspicious VUS across ancestry groups ranged from 15 to 20%, compared to only 10% among Europeans. Even when the clinical diagnosis was uncertain, those with the most monogenic disease features had the greatest diagnostic yield from genetic testing.

CONCLUSIONS

Research-focused efforts can increase the diagnostic yield by up to 5%. Where a variant is identified, this will have clinical utility beyond family screening in 13%. We demonstrate the value of genomics in reaching an overall diagnosis and highlight inequities based on ancestry. Acknowledging our incomplete understanding of disease phenotypes, we propose a framework for prioritising likely monogenic cases to solve their underlying cause of disease.

Clinical Profile and Health Disparities in a Multiethnic Cohort of Patients With Hypertrophic Cardiomyopathy

BACKGROUND

Clinical studies of hypertrophic cardiomyopathy are over-represented by individuals of European ethnicity, with less known about other ethnic groups. We investigated differences between patients in a multiethnic Australian hypertrophic cardiomyopathy population.

METHODS

We performed a retrospective cohort study of 836 unrelated hypertrophic cardiomyopathy probands attending a specialized clinic between 2002 and 2020. Major ethnic groups were European (n=611), East Asian (n=75), South Asian (n=58), and Middle Eastern and North African (n=68). The minor ethnicity groups were Oceanian (n=9), People of the Americas (n=7), and African (n=8). One-way ANOVA with Dunnett post hoc test and Bonferroni adjustment were performed.

RESULTS

Mean age of the major ethnic groups was 54.9±16.9 years, and 527 (65%) were male. Using the European group as the control, East Asian patients had a lower body mass index (29 versus 25 kg/m², P<0.0001). South Asians had a lower prevalence of atrial fibrillation (10% versus 31%, P=0.024). East Asians were more likely to have apical hypertrophy (23% versus 6%, P<0.0001) and Middle Eastern and North African patients more likely to present with left ventricular outflow tract obstruction (46% versus 34%, P=0.0003). East Asians were less likely to undergo genetic testing (55% versus 85%, P<0.0001) or have an implantable cardioverter-defibrillator implanted (19% versus 36%, P=0.037). East Asians were more likely to have a causative variant in a gene other than MYBPC3 or MYH7, whereas Middle Eastern and North African and South Asians had the highest rates of variants of uncertain significance (27% and 21%, P<0.0001).

CONCLUSIONS

There are few clinical differences based on ethnicity, but importantly, we identify health disparities relating to access to genetic testing and implantable cardioverter-defibrillator use. Unless addressed, these gaps will likely widen as we move towards precision-medicine-based care of individuals with hypertrophic cardiomyopathy.

Hypertrophic Cardiomyopathy: Genetic Testing and Risk Stratification

PURPOSE OF REVIEW

Our knowledge of the genetic basis and molecular pathogenesis of hypertrophic cardiomyopathy (HCM) continues to evolve. We describe the genetic basis of HCM, recent advances in genetic testing and the role of genetics in guiding risk stratification and management, both now and in the future.

RECENT FINDINGS

While initially thought to be an exclusively Mendelian disease, we now know there are important HCM sub-groups. A proportion will have sarcomere variants as the cause of their disease, while others will have genetic variants in genes that can give rise to conditions that can mimic HCM. The role of genetics is primarily for cascade genetic testing, though there is emerging evidence of a role for prognosis and patient management. Genetic testing is a useful addition to management. Genotype may play a greater role in risk stratification, management, treatment and prognosis in future, offering improved outcomes for patients and their families with HCM.

Necrotising otitis externa: an unusual cause of cranial nerve palsy in a diabetic haemodialysis patient

We present an unusual case of necrotising otitis externa (NOE) causing a lower motor neurone facial nerve palsy in a patient with diabetes mellitus and receiving maintenance haemodialysis for end-stage renal disease (ESRD). Pseudomonas aeruginosa is the most common pathogen isolated in NOE, although our case involved the non-typical pathogens Aspergillus flavus and Proteus mirabilis. We discuss the need for diagnostic rigour and the importance of considering atypical infective pathology in patients with ESRD or diabetes mellitus. We review NOE with reference to causative agents, imaging strategies, prognostic indicators and treatment.

Deterioration of giant cell arteritis with corticosteroid therapy

BACKGROUND

Failure of response of giant cell arteritis (GCA) to corticosteroid therapy has invariably been attributed to the delay in diagnosing the disease or the use of inadequate corticosteroid dosage. Following our observation of progressive deterioration following the introduction of prednisolone use in a patient, we examined the possibility that worsening of the condition might be due to corticosteroid therapy rather than coincidence.

OBJECTIVE

To determine whether corticosteroid therapy may exacerbate GCA. DESLGN: Case report and an analysis of similar cases reported in the medical literature.

PATIENT

A 64-year-old man had a 3-month history of headache, night sweats, malaise and general weakness, and anorexia and weight loss and a more recent history of jaw claudication, dysphagia, and hoarseness. Clinical findings included prominent temporal arteries with absent pulsation, abnormal saccades to the right, and eyelid retraction. Laboratory findings included an elevated erythrocyte sedimentation rate and platelet count. Results of a biopsy of the temporal artery confirmed GCA. Magnetic resonance imaging scans showed ischemic cerebellar lesions and a mature infarct in the left anterior occipital, posteroparietal region. Following corticosteroid therapy commencement, the patient's condition deteriorated steadily for 5 days with clinical signs suggestive of an evolving vertebrobasilar stroke. Following treatment with high-dose intravenous dexamethasone sodium phosphate and heparin sodium, his symptoms improved.

DATA SOURCES

The review included analysis of autopsy-based reports in which clinical details are provided and clinical reports in which major visual or cerebral complications are described. Significant complications occurred in many cases shortly following the introduction of corticosteroid therapy. In many of these cases, the symptoms indicated that GCA had been present for a significant period prior to corticosteroid therapy.

CONCLUSIONS

Progressively evolving occlusive strokes may occur following corticosteroid therapy in patients with GCA. In cerebrovascular complications, vascular occlusion occurs at sites of active vasculitis, usually within the vertebrobasilar system. It is not certain that the worsening of the condition following corticosteroid therapy is always coincidental, and an alternative possibility, namely a functional relationship between the initiation of corticosteroid therapy and clinical deterioration, should be borne in mind.

A traumatic ossicular disruption successfully repaired with n-butyl cyanoacrylate tissue adhesive

Tissue adhesives have been available and in use for more than 40 years. They have, however, never been popular for ossiculoplasty because of the reported excessive inflammatory reaction and ototoxicity. The authors present a case of ossicular disruption successfully repaired with tissue adhesive and review the literature.

Percussion of the chest re-visited: a comparison of the diagnostic value of ausculatory and conventional chest percussion

Percussion of the chest is thought to be insensitive in detecting small or deeply situated chest lesions. A newer technique, ausculatory percussion, has been reported as having a far higher sensitivity. In a controlled blind study the diagnostic value of conventional chest percussion compared with ausculatory percussion was defined using the chest x-ray as a gold standard. The prevalence of disease in 100 lung fields was 26%. The majority of lesions were not detected by either technique resulting in very low sensitivities of 15.4% for conventional percussion and 19.2% for ausculatory percussion. A positive result with ausculatory percussion was twice as likely to be false as true (positive predictive value 31.2%). The technique did not add to the diagnostic value of conventional percussion. Both techniques have major limitations. Patients with suspected lung disease still require chest x-ray examination if percussion is normal.