Case report: Biallelic variants in POLR3B gene lead to 4H leukodystrophy from the study of brother and sister

4H leukodystrophy, one of POLR3-related leukodystrophy, is a rare hereditary brain white matter disease caused by the pathogenic biallelic variations in POLR3A, POLR3B, or POLR1C. Hypomyelination, hypodontia, and hypogonadotropic hypogonadism is mainly presented in patients with 4H leukodystrophy. PATIENT CONCERNS: Here, we reported the brother and the sister with new compound heterozygous (c.1615G>T and c.165-167del) with various degrees of phenotypes including dysbasia, myopia, dental abnormal, and hypogonadotropic hypogonadism. DIAGNOSIS: The brother and sister were diagnosed with 4H leukodystrophy. INTERVENTIONS: Gonadotrophins treatment of the brother could significantly improve the development of secondary sexual characteristics and genitalia. OUTCOMES: This study showed that the same genotype of POLR3B may have variable clinical phenotypes in the brother and sister. CONCLUSION: The exploration of molecular functions and genetic counseling are crucial for further diagnosis and treatment of POLR3-related leukodystrophy.