LEOPARD syndrome (LS) is a form of RASopathy caused by mutations in the PTPN11 gene an upstream regulator of RAS/MAPK signaling. Although hypertrophic cardiomyopathy (HCM) is a shared cardiac phenotype among RASopathies, HCM complicating patients with LS is characteristic for its unique early-onset and progressive features.

We herein report a neonate with LS who presented with an extremely severe form of HCM. Autopsy revealed remarkable evidence of active cardiomyocyte proliferation contributing to the overt cardiomegaly. The case suggests an intriguing association between the observed dramatic increase in cardiomyocyte mitotic activity and the fatal clinical course of LS-associated HCM.

The patient was the second daughter born to nonconsanguineous parents with no significant family history. Marked biventricular hypertrophy was noted on fetal echocardiography at the 28th week of gestation. After an uneventful delivery, the patient was immediately admitted to the neonatal intensive care unit. Physical examination at birth revealed multiple dysmorphic features, including a wide forehead, low set ears, hypertelorism, and wide set nipples. No skin lesions, such as café-au-lait spots or lentigines, were noticed, whereas mild hearing loss was detected by newborn screening. The findings were suggestive of LS. Imaging studies were remarkable for cardiomegaly (Figure …

LEOPARD综合征（LS）是RAS病的一种形式，是由PTPN11基因（RAS / MAPK信号的上游调节剂）中的突变引起的。尽管肥厚型心肌病（HCM）是RA社交病患者之间共享的心脏表型，但使LS合并症的HCM因其独特的早期发作和进行性特征而具有特征性。

我们在此报告了一名患有LS的新生儿，其表现为一种极其严重的HCM形式。尸检揭示了活跃的心肌细胞增殖导致明显的心肌肿大的明显证据。该病例表明，在观察到的心肌细胞有丝分裂活性急剧增加与LS相关HCM的致命临床过程之间存在着有趣的联系。

该患者是无血缘父母的第二个女儿，没有明显的家族史。妊娠第28周在胎儿超声心动图上发现明显的双室肥大。分娩顺利后，患者立即被送入新生儿重症监护室。出生时进行的体格检查发现了多种畸形特征，包括额头宽大，耳朵低位，体力亢进和乳头宽大。没有发现任何皮肤损伤，例如咖啡色斑点或长春新碱，而新生儿筛查发现轻度听力下降。该发现提示LS。影像学检查对于心脏肿大非常显着（图……）