MedGen

Neurodevelopmental disorder with hypotonia and dysmorphic facies (NEDHYDF) is characterized by global developmental delay and hypotonia apparent from birth. Affected individuals have variably impaired intellectual development, often with speech delay and delayed walking. Seizures are generally not observed, although some patients may have single seizures or late-onset epilepsy. Most patients have prominent dysmorphic facial features. Additional features may include congenital cardiac defects (without arrhythmia), nonspecific renal anomalies, joint contractures or joint hyperextensibility, dry skin, and cryptorchidism. There is significant phenotypic variability in both the neurologic and extraneurologic manifestations (summary by Tan et al., 2022). [from OMIM]

Sick sinus syndrome-4 (SSS4) is characterized by early and progressive sinus node and atrioventricular conduction dysfunction. Patients show bradycardia and chronotropic incompetence, and may experience syncope. Atrioventricular conduction block ranges from mild to severe, and some patients also have intermittent atrial fibrillation. Many require implantation of a pacemaker, but sudden cardiac death has not been reported (Stallmeyer et al., 2017). For a general phenotypic description and discussion of genetic heterogeneity of sick sinus syndrome, see SSS1 (608567). [from OMIM]