Multiple congenital anomalies-hypotonia-seizures syndrome-4 (MCAHS4) is an autosomal recessive neurologic disorder characterized by onset of refractory seizures in the first months of life. Patients have severe global developmental delay, and may have additional variable features, including dysmorphic or coarse facial features, visual defects, and mild skeletal or renal anomalies. At the cellular level, the disorder is caused by a defect in the synthesis of glycosylphosphatidylinositol (GPI), and thus affects the expression of GPI-anchored proteins at the cell surface (summary by Starr et al., 2019). For a discussion of genetic heterogeneity of MCAHS, see MCAHS1 (614080). For a discussion of genetic heterogeneity of DEE, see 308350. For a discussion of genetic heterogeneity of GPI biosynthesis defects, see GPIBD1 (610293).

Carey-Fineman-Ziter syndrome-2 (CFZS2) is an autosomal recessive disorder characterized by weakness of the facial musculature, hypomimic facies, increased overbite, micrognathia, and facial dysmorphism. Other features may include failure to thrive, axial hypotonia, and progressive scoliosis (Ramirez-Martinez et al., 2022). For a discussion of genetic heterogeneity of Carey-Fineman-Ziter syndrome, see CFZS1 (254940).