Multisystem disorder and limb girdle muscular dystrophy caused by LMNA p.R28W mutation

Cardiac phenotype in familial partial lipodystrophy

OBJECTIVES

LMNA variants have been previously associated with cardiac abnormalities independent of lipodystrophy. We aimed to assess cardiac impact of familial partial lipodystrophy (FPLD) to understand the role of laminopathy in cardiac manifestations.

STUDY DESIGN

Retrospective cohort study.

METHODS

Clinical data from 122 patients (age range: 13-77, 101 females) with FPLD were analysed. Mature human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with an LMNA variant were studied as proof-of-concept for future studies.

RESULTS

Subjects with LMNA variants had a higher prevalence of overall cardiac events than others. The likelihood of having an arrhythmia was significantly higher in patients with LMNA variants (OR: 3.77, 95% CI: 1.45-9.83). These patients were at higher risk for atrial fibrillation or flutter (OR: 5.78, 95% CI: 1.04-32.16). The time to the first arrhythmia was significantly shorter in the LMNA group, with a higher HR of 3.52 (95% CI: 1.34-9.27). Non-codon 482 LMNA variants were more likely to be associated with cardiac events (vs. 482 LMNA: OR: 4.74, 95% CI: 1.41-15.98 for arrhythmia; OR: 17.67, 95% CI: 2.45-127.68 for atrial fibrillation or flutter; OR: 5.71, 95% CI: 1.37-23.76 for conduction disease). LMNA mutant hiPSC-CMs showed a higher frequency of spontaneous activity and shorter action potential duration. Functional syncytia of hiPSC-CMs displayed several rhythm alterations such as early afterdepolarizations, spontaneous quiescence and spontaneous tachyarrhythmia, and significantly slower recovery in chronotropic changes induced by isoproterenol exposure.

CONCLUSIONS

Our results highlight the need for vigilant cardiac monitoring in FPLD, especially in patients with LMNA variants who have an increased risk of developing cardiac arrhythmias. In addition, hiPSC-CMs can be studied to understand the basic mechanisms for the arrhythmias in patients with lipodystrophy to understand the impact of specific mutations.

Lipodystrophies, dyslipidaemias and atherosclerotic cardiovascular disease

Lipodystrophies are rare, heterogeneous, genetic or acquired, disorders characterised by varying degrees of body fat loss and associated metabolic complications, including insulin resistance, dyslipidaemias, hepatic steatosis and predisposition to atherosclerotic cardiovascular disease (ASCVD). The four main types of lipodystrophy, excluding antiretroviral therapy-induced lipodystrophy in HIV-infected patients, are congenital generalised lipodystrophy (CGL), familial partial lipodystrophy (FPLD), acquired generalised lipodystrophy (AGL) and acquired partial lipodystrophy (APL). This paper reviews the literature related to the prevalence of dyslipidaemias and ASCVD in patients with lipodystrophies. Patients with CGL, AGL and FPLD have increased prevalence of dyslipidaemia but those with APL do not. Patients with CGL as well as AGL present in childhood, and have severe dyslipidaemias (mainly hypertriglyceridaemia) and early onset diabetes mellitus as a consequence of extreme fat loss. However, only a few patients with CGL and AGL have been reported to develop coronary heart disease. In contrast, data from some small cohorts of FPLD patients reveal increased prevalence of ASCVD especially among women. Patients with APL have a relatively low prevalence of hypertriglyceridaemia and diabetes mellitus. Overall, patients with lipodystrophies appear to be at high risk of ASCVD due to increased prevalence of dyslipidaemia and diabetes and efforts should be made to manage these metabolic complications aggressively to prevent ASCVD.

[A complex case of diabetes due to LMNA mutation]

INTRODUCTION

Laminopathies (diseases related to A/C mutations of lamines) are rare genetic diseases with an extensive phenotypic spectrum, including lipodystrophic syndromes-characterized by a selective loss of adipose tissue-of which the partial Dunnigan family type is the most frequent.

CASE REPORT

We report on a 55-year-old woman with diabetes and long-term disabling myalgia. Her cushingoid morphotype, associated with cutaneous lipo-atrophy and muscle hypertrophy in addition to a genetic heritage, led us to the diagnosis of complex partial familial lipodystrophy heterozygous LMNA_c.82C>T, p.Arg28Trp mutation.

CONCLUSION

Familial partial lipodystrophic syndromes may have varied phenotypes, mainly cardio-metabolic, which could mimic a particularly severe type 2 diabetes. The diagnostic work-up of this disease has to include a careful investigation of gait troubles and paroxysmal conduction that could lead to sudden death, as well as a genetic examination. In some cases, recombinant leptin can be proposed.