A case of the Kugelberg-Welander syndrome complicated with cardiac lesions

Developmental and degenerative cardiac defects in the Taiwanese mouse model of severe spinal muscular atrophy

Spinal muscular atrophy (SMA), an autosomal recessive disease caused by a decrease in levels of the survival motor neuron (SMN) protein, is the most common genetic cause of infant mortality. Although neuromuscular pathology is the most severe feature of SMA, other organs and tissues, including the heart, are also known to be affected in both patients and animal models. Here, we provide new insights into changes occurring in the heart, predominantly at pre- and early symptomatic ages, in the Taiwanese mouse model of severe SMA. Thinning of the interventricular septum and dilation of the ventricles occurred at pre- and early symptomatic ages. However, the left ventricular wall was significantly thinner in SMA mice from birth, occurring prior to any overt neuromuscular symptoms. Alterations in collagen IV protein from birth indicated changes to the basement membrane and contributed to the abnormal arrangement of cardiomyocytes in SMA hearts. This raises the possibility that developmental defects, occurring prenatally, may contribute to cardiac pathology in SMA. In addition, cardiomyocytes in SMA hearts exhibited oxidative stress at pre-symptomatic ages and increased apoptosis during early symptomatic stages of disease. Heart microvasculature was similarly decreased at an early symptomatic age, likely contributing to the oxidative stress and apoptosis phenotypes observed. Finally, an increased incidence of blood retention in SMA hearts post-fixation suggests the likelihood of functional defects, resulting in blood pooling. These pathologies mirror dilated cardiomyopathy, with clear consequences for heart function that would likely contribute to potential heart failure. Our findings add significant additional experimental evidence in support of the requirement to develop systemic therapies for SMA capable of treating non-neuromuscular pathologies.

Electrocardiographic Evaluation in Patients With Spinal Muscular Atrophy: A Case-Control Study

BACKGROUND

This study aimed to show the impairment of autonomic cardiac conduction causing bradycardia and/or electrocardiographic alterations in children affected by spinal muscular atrophy type 1 and 2 (SMA 1 and 2).

METHODS

We included 25 spinal muscular atrophy patients, admitted from November 2016 to May 2017. All patients underwent an electrocardiographic examination and we studied PR and QRS intervals, P-waves and QRS amplitudes, and heart rate in spinal muscular atrophy patients compared to a control group.

RESULTS

In all patients, we found longer PRi and QRSi ( P < .05), lower P-wave and QRS complex amplitudes ( P < .01), and a decreased heart rate ( P < .01) with respect to controls. When we divided our patients into SMA1 and SMA2 subgroups, we found that statistical differences were maintained for P-wave and QRS complex amplitudes and heart rate, but not for PRi and QRSi with respect to controls.

CONCLUSION

We suggest the hypothesis of SMN expression on cardiac tissue condition and/or autonomic cardiac conduction.

Cardiac pathology in spinal muscular atrophy: a systematic review

Background

Hereditary proximal spinal muscular atrophy (SMA) is a severe neuromuscular disease of childhood caused by homozygous loss of function of the survival motor neuron (SMN) 1 gene. The presence of a second, nearly identical SMN gene (SMN2) in the human genome ensures production of residual levels of the ubiquitously expressed SMN protein. Alpha-motor neurons in the ventral horns of the spinal cord are most vulnerable to reduced SMN concentrations but the development or function of other tissues may also be affected, and cardiovascular abnormalities have frequently been reported both in patients and SMA mouse models.

Methods

We systematically reviewed reported cardiac pathology in relation to SMN deficiency. To investigate the relevance of the possible association in more detail, we used clinical classification systems to characterize structural cardiac defects and arrhythmias.

Conclusions

Seventy-two studies with a total of 264 SMA patients with reported cardiac pathology were identified, along with 14 publications on SMA mouse models with abnormalities of the heart. Structural cardiac pathology, mainly septal defects and abnormalities of the cardiac outflow tract, was reported predominantly in the most severely affected patients (i.e. SMA type 1). Cardiac rhythm disorders were most frequently reported in patients with milder SMA types (e.g. SMA type 3). All included studies lacked control groups and a standardized approach for cardiac evaluation.

The convergence to specific abnormalities of cardiac structure and function may indicate vulnerability of specific cell types or developmental processes relevant for cardiogenesis. Future studies would benefit from a controlled and standardized approach for cardiac evaluation in patients with SMA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-017-0613-5) contains supplementary material, which is available to authorized users.

Is spinal muscular atrophy a disease of the motor neurons only: pathogenesis and therapeutic implications?

Spinal muscular atrophy (SMA) is a genetic neurological disease that causes infant mortality; no effective therapies are currently available. SMA is due to homozygous mutations and/or deletions in the survival motor neuron 1 gene and subsequent reduction of the SMN protein, leading to the death of motor neurons. However, there is increasing evidence that in addition to motor neurons, other cell types are contributing to SMA pathology. In this review, we will discuss the involvement of non-motor neuronal cells, located both inside and outside the central nervous system, in disease onset and progression. Even if SMN restoration in motor neurons is needed, it has been shown that optimal phenotypic amelioration in animal models of SMA requires a more widespread SMN correction. It has been demonstrated that non-motor neuronal cells are also involved in disease pathogenesis and could have important therapeutic implications. For these reasons it will be crucial to take this evidence into account for the clinical translation of the novel therapeutic approaches.

Cardiac involvement in Kugelberg-Welander disease: a case report and review

There are few reports of cardiac involvement in patients with Kugelberg-Welander disease. We report a case of a 51-year-old man with Kugelberg-Welander disease who presented with syncope. His electrocardiogram showed complete right bundle branch block and transient complete atrioventricular block without escape rhythm. He was successfully treated with emergency temporary pacing followed by permanent pacemaker implantation. In this report, we review the relevant literature and argue that patients with Kugelberg-Welander disease should be evaluated regularly for cardiac disease.

Atrial standstill in a case of Kugelberg-Welander syndrome with cardiac involvement: an electrophysiologic study

A patient with Kugelberg-Welander syndrome associated with junctional rhythm and restrictive cardiomyopathy is presented. An electrophysiologic study was performed. Persistent atrial standstill was demonstrated by detailed right atrium and coronary sinus mapping and failure of capture of both right atrium and coronary sinus pacing. A prolonged junctional recovery time, normal HV interval and normal pacing threshold of the right ventricle were also noted. The patient was successfully treated with cardiac pacing and diuretics.

[Cardiac involvement in neuromuscular diseases]

Many neuromuscular disorders involve the heart, occasionally with overt clinical disease. Muscular dystrophies (dystrophinopathies, limb girdle muscular dystrophy, Emery-Dreifuss muscular dystrophy, Steinert's myotonic dystrophy), congenital myopathies, inflammatory myopathies and metabolic diseases (glycogenosis, periodic paralysis, mitochondrial diseases) may produce dilated or hypertrophic cardiomyopathy and heart rhythm or conduction disturbances. Furthermore the heart is commonly involved in some hereditary and degenerative diseases (Friedreich's ataxia and Kugelberg-Welander syndrome) and acquired (Guillain-Barré syndrome) or inherited (Refsum's disease and Charcot-Marie-Tooth syndrome) polyneuropathies. A cardiologist's high clinical suspicion and a simple but systematic skeletal muscle and peripheral nerve investigation, including muscle enzymes quantification, neurophysiological study and muscle biopsy, are necessary for an accurate diagnosis. In selected patients, more sophisticated biochemical and genetic analysis will be necessary. In most cases, endomyocardial biopsy is not essential for the diagnosis.

Heart disease in myasthenia gravis

Patients with myasthenia gravis (MG) may develop heart disease. Our data on 108 MG patients were examined to assess the type and frequency of this. 17 of 108 patients (16%) showed signs of heart disease which could be regarded as MG-related. 11 of these, of whom 5 died suddenly, had clinical symptoms, mainly arrhythmias. Signs of heart disease were most frequent in thymoma patients (5 of 10), and all 3 microscopically examined hearts from these patients showed a focal myocarditis. 44 spinal muscular atrophy patients serving as controls showed a 16% frequency of signs of heart disease of unknown etiology. However, only 1 of 44 spinal muscular atrophy patients (2%) had clinical symptoms as compared to 11 of 108 MG patients (10%). Together with the characteristic focal nature of the myocarditis and the microscopic similarities between lesions of heart and skeletal muscle, this indicates that the heart disease is specifically related to MG.