Clinical and cardiovascular magnetic resonance profile of cardiomyopathy patients from South Africa: Pilot of the IMHOTEP study

BACKGROUND

Cardiomyopathy is an important cause of heart failure, however, there is notable lack of data on causes and manifestations of cardiomyopathy in Africa.

AIMS

The African Cardiomyopathy and Myocarditis Registry Program (IMHOTEP) aims to address the knowledge gap on etiology, treatment, and outcomes of cardiomyopathy in sub-Saharan Africa.

METHODS AND RESULTS

We conducted a single-center pilot study to delineate the clinical and cardiovascular magnetic resonance (CMR) phenotypes of cardiomyopathy in South African patients. Assessment of the first 99 adult incident cases [mean age 36.8 ± 12.5 years; females 53.5%] enrolled in IMHOTEP showed that dilated cardiomyopathy (n = 77) was commonest, followed by hypertrophic (n = 13), restrictive (n = 5) and arrhythmogenic (n = 4) cardiomyopathies. A broad range of etiologies were encountered with secondary causes identified in 42% of patients. Onset of symptoms in the peripartum period was observed in 47% of women, and peripartum cardiomyopathy was diagnosed in 32.1% of women recruited. In addition to electrocardiography and echocardiography, CMR was performed in 67 cases and contributed diagnostically in a third of cases. Acute inflammation was rarely observed [2%] on CMR, however, late gadolinium enhancement (LGE) was noted in 92% of cases.

CONCLUSION

We report a diverse spectrum of causes of cardiomyopathy in the South African population, with secondary, potentially treatable, etiologies in a significant proportion of cases. CMR was useful in delineating specific phenotypes and etiologies, influencing clinical care. A higher-than-expected burden of LGE was observed in this young patient cohort - the implications of which are yet to be determined.

Heterozygous CAPN3 missense variants causing autosomal-dominant calpainopathy in seven unrelated families

AIMS

Recessive variants in CAPN3 gene are the cause of the commonest form of autosomal recessive limb girdle muscle dystrophy. However, two distinct in-frame deletions in CAPN3 (NM_000070.3:c.643_663del21 and c.598_621del15) and more recently, Gly445Arg and Arg572Pro substitutions have been linked to autosomal dominant (AD) forms of calpainopathy. We report 21 affected individuals from seven unrelated families presenting with an autosomal dominant form of muscular dystrophy associated with five different heterozygous missense variants in CAPN.

METHODS

We have used massively parallel gene sequencing (MPS) to determine the genetic basis of a dominant form of limb girdle muscular dystrophy in affected individuals from seven unrelated families.

RESULTS

The c.700G> A, [p.(Gly234Arg)], c.1327T> C [p.(Ser443Pro], c.1333G> A [p.(Gly445Arg)], c.1661A> C [p.(Tyr554Ser)] and c.1706T> C [p.(Phe569Ser)] CAPN3 variants were identified. Affected individuals presented in young adulthood with progressive proximal and axial weakness, waddling walking and scapular winging or with isolated hyperCKaemia. Muscle imaging showed fatty replacement of paraspinal muscles, variable degrees of involvement of the gluteal muscles, and the posterior compartment of the thigh and minor changes at the mid-leg level. Muscle biopsies revealed mild myopathic changes. Western blot analysis revealed a clear reduction in calpain 3 in skeletal muscle relative to controls. Protein modelling of these variants on the predicted structure of calpain 3 revealed that all variants are located in proximity to the calmodulin-binding site and are predicted to interfere with proteolytic activation.

CONCLUSIONS

We expand the genotypic spectrum of CAPN3-associated muscular dystrophy due to autosomal dominant missense variants.

6133Profile of cardiomyopathy patients in Cape Town - pilot phase the IMHOTEP Study

Background

Cardiomyopathies pose a great challenge because of poor prognosis and high prevalence in LMIC with limited access to specialised care. Little is known about the clinical profile of cardiomyopathy in Africa.

Purpose

Delineation of clinical presentation and cardiovascular magnetic resonance (CMR) phenotypes of cardiomyopathy.

Method

The African Cardiomyopathy and Myocarditis Registry Program (IMHOTEP) is a prospective multi-centre, hospital-based study and aims to investigate the clinical characteristics, aetiology, genetics, management and outcomes of cardiomyopathies in Africans.

Results

Assessment of the first 99 adult cases showed that dilated cardiomyopathy (DCM; n=67) was commonest, followed by hypertrophic (HCM; n=13), left ventricular noncompaction (LVNC; n=11), restrictive (RCM; n=4) and arrhythmogenic (ARVC; n=4) cardiomyopathies. Idiopathic DCM (22%) and peripartum cardiomyopathy (16%) accounted for the majority (Figure). A family history of cardiomyopathy or SCD was reported in 20% of cases. Mean age of presentation was 37±12 years. Most patients (96%) were symptomatic at presentation. NYHA class III/IV was more frequently seen in DCM (61%), RCM (50%) and LVNC (64%), whereas syncope was more common in ARVC (50%) and HCM (23%). VT and aborted cardiac arrest were reported in 7% and 3%, respectively. Onset of symptoms in the peripartum period was observed in 47% of women. Beta-blockers and ACE-inhibitors were prescribed in 77% and 78%, respectively, however optimal dosing was achieved in ≤14% of patients at a median time of 5.4 months after symptom onset. CMR was performed in 67 (68%) cases (Table) and contributed diagnostically in a third of cases. Late gadolinium enhancement (LGE) was observed in 92%. In DCM, linear mid-wall and subendocardial patterns of LGE were seen in 95% and 8% of patients respectively – a much higher percentage than previously reported in the literature.

CMR volumetric and functional assessment DCM, n=38 HCM, n=11 ARVC, n=3 RCM, n=4 LVNC, n=11 LVEF (%) 27±15 78±7 55±5 52±7 32±17 LVEDV/BSA (ml/m2) 150±40 80±17 98±12 59±13 155±52 LV mass/BSA (g/m2) 82±23 102±35 74±3 71±14 88±31 RVEF (%) 34±15 68±10 22±15 49±18 33±15 RVEDV/BSA (ml/m2) 104±37 68±15 189±27 56±8 106±51 All continuous variables presented as mean ± standard deviation.

Cardiomyopathy diagnosis (n=99)

Conclusion

IMHOTEP is the first multi-centre registry for cardiomyopathy in Africa. Preliminary data suggests an earlier age of onset with female predominance compared to other cohorts, and DCM is the predominant form of cardiomyopathy in Africa.

Acknowledgement/Funding

NEWTON FUND NON-COMMUNICABLE DISEASE - South African Medical Research Council (SAMRC/GSK)

[Myosin storage myopathy: a rare subtype of protein aggregate myopathies]

Myopathies with pathological protein aggregates comprise a numerically significant group of sporadic and hereditary muscle disorders. A rare disease entity within the group of protein aggregate myopathies is the myosin storage myopathy, which is caused by heterozygous mutations in the MYH7 gene which encodes the slow/beta-myosin heavy chain. We report the clinical, myopathological and MRI findings in the first German patient suffering from a myosin storage myopathy due to a heterozygous R 1845W missense mutation.

Adenovirus and adeno-associated virus-mediated delivery of human myophosphorylase cDNA and LacZ cDNA to muscle in the ovine model of McArdle's disease: expression and re-expression of glycogen phosphorylase

At present there is no satisfactory treatment for McArdle's disease, deficiency of myophosphorylase. Injection of modified adenovirus 5 (AdV5) and adeno-associated virus 2 (AAV2) vectors containing myophosphorylase expression cassettes, into semitendinosus muscle of sheep with McArdle's disease, produced expression of functional myophosphorylase and some re-expression of the non-muscle glycogen phosphorylase isoforms (both liver and brain) in regenerating fibres. Expression of both non-muscle isoforms was also seen after control injections of AdV5LacZ vectors. There was up to an order of magnitude greater expression of phosphorylase after myophosphorylase vector injection than after LacZ controls (62% of sections with over 1000 positive muscle fibres, versus 7%). The results presented here suggest that the use of viral vector-mediated phosphorylase gene transfer may be applicable to the treatment of McArdle's disease and that sustained re-expression of the brain and liver isoforms should also be investigated as a possible treatment.

Nemaline myopathy with exclusively intranuclear rods and a novel mutation in ACTA1 (Q139H)

Nemaline myopathies (NM) are a rare group of muscle disorders, but represent one of the most common forms of congenital myopathy. The clinical picture ranges from severe muscular hypotonia often leading to death during childhood to mild forms with long life expectancy. Diagnosis is made by muscle biopsy showing characteristic sarcoplasmic and sometimes intranuclear rod bodies. So far, disease-associated mutations have been detected in six genes without any simple correlation between genotype and phenotype or histological findings. We report a patient with a phenotype typical of congenital onset nemaline myopathy and exclusively intranuclear rods. Mutation analysis revealed a new heterozygous missense mutation in exon 3 of the ACTA1 gene (Q139H). Molecular modelling predicts that substitution of Q139 for H139 alters the amino acid side chains and hydrogen bonding which may alter the nucleotide binding cleft by adding 'bulk' to the mutated molecule. Two-dimensional gel electrophoresis demonstrates that mutant actin Q139H is expressed at approximately half the level of wild-type actin in the patient's muscle. We speculate that these alterations, although not directly affecting the nuclear export signal, negatively interfere with the nuclear export of the mutated protein and thereby cause retention of mutant actin and intranuclear rod formation.

Macrolide resistance mechanisms among Streptococcus pneumoniae isolated over 6 years of Canadian Respiratory Organism Susceptibility Study (CROSS) (1998 2004)

BACKGROUND

Resistance to macrolides in Streptococcus pneumoniae arises primarily due to Erm(B) or Mef(A). Erm(B) typically confers high-level resistance to macrolides, lincosamides and streptogramin B (MLS(B) phenotype), whereas Mef(A) confers low-level resistance to macrolides only (M phenotype). The purpose of this study was to investigate the incidence of macrolide resistance mechanisms in Canadian isolates of S. pneumoniae obtained between 1998 and 2004. Furthermore, the genetic relatedness, serotype distribution and antibiotic susceptibility profile among S. pneumoniae isolates with dual erythromycin ribosomal methylase [Erm(B)] and efflux pump [Mef(A)] were analysed.

METHODS

A total of 865 macrolide-resistant (erythromycin MIC > or = 1 mg/L) S. pneumoniae isolates were collected from the Canadian Respiratory Organism Susceptibility Study (CROSS) from 1998 to 2004. The presence of erm(B) and mef(A) was determined for each isolate by PCR; mutations in the genes coding for L4 and L22 ribosomal proteins and for 23S rRNA were identified by DNA sequencing. Each isolate containing both erm(B)- and mef(A)-mediated macrolide resistance was genotyped by PFGE and serotyped using the Quellung reaction with antisera.

RESULTS

Of the 865 isolates studied, 404 (46.7%) were mef(A)-positive, 371 (42.9%) were erm(B)-positive, 50 (5.8%) were positive for both mef(A) and erm(B) and 40 (4.6%) were negative for both mef(A) and erm(B). Of the macrolide-resistant isolates negative for both mef(A) and erm(B), 22 (2.5%) contained 23S rRNA A2058G, A2059G or A2059C mutations, 7 (0.8%) contained 23S rRNA A2058G or A2059G mutations along with an S20N mutation in L4 ribosomal protein, and 1 isolate contained an E30K ribosomal protein mutation alone. Of the macrolide-resistant strains positive for both mef(A) and erm(B), 36 (72%) were multidrug-resistant (macrolide-, penicillin- and trimethoprim/sulfamethoxazole-resistant), 39 (78%) isolates belonged to serotype 19A or 19F and 36 (72%) belonged to one clonal complex (> or =80% genetic relatedness) genetically related to the Taiwan 19F-14 clone.

CONCLUSIONS

The prevalence of efflux-based macrolide resistance in S. pneumoniae in Canada remained steady between 1998 and 2004. Macrolide resistance due to erm(B) decreased over the same time period, with a rapid increase in isolates with both erm(B) and mef(A) macrolide resistance.

'Cap myopathy': case report of a family

We report the observation of an 18-year-old girl, whose clinical presentation was very suggestive of a congenital myopathy with neonatal onset. A congenital myopathy had been already diagnosed in her brother and in addition her half-cousin died diagnosed with a severe nemaline myopathy at age 4 years. A muscle biopsy performed on both siblings revealed histological and ultrastructural features of 'cap myopathy'. This case report suggests that 'cap myopathy' and some cases of nemaline myopathy with neonatal onset might be two phenotypic expressions of the same genetic disorder. These two entities could therefore, perhaps, be regarded as 'Z-line disorders' possibly caused by defective myofibrillogenesis.