Cartilage-hair hypoplasia-anauxetic dysplasia spectrum disorders harboring RMRP mutations in two Korean children: A case report.

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Cartilage-hair hypoplasia (CHH, OMIM # 250250) is a rare autosomal recessive disorder, which includes cartilage-hair hypoplasia-anauxetic dysplasia (CHH-AD) spectrum disorders. CHH-AD is caused by homozygous or compound heterozygous mutations in the RNA component of the mitochondrial RNA-processing Endoribonuclease (RMRP) gene. Here, we report 2 cases of Korean children with CHH-AD. In the first case, the patient had metaphyseal dysplasia without hypotrichosis, diagnosed by whole exome sequencing (WES), and exhibited only skeletal dysplasia and lacked extraskeletal manifestations, such as hair hypoplasia and immunodeficiency. In the second case, the patient had skeletal dysplasia, hair hypoplasia, and immunodeficiency, which were identified by WES. The second case is the first CHH reported in Korea. The patients in both cases received regular immune and lung function checkups. Our cases suggest that children with extremely short stature from birth, with or without extraskeletal manifestations, should include CHH-AD as a differential diagnosis. Clinical suspicion is the most important and RMRP sequencing should be considered for the diagnosis of CHH-AD.