RMRP and immunodeficiency disease: Cartilage-hair hypoplasia (CHH) is an autosomal recessive disorder caused by homozygous or compound heterozygous mutations in the RMRP gene, which is extremely rare in the population, and its most common feature is disproportionately short limb shortness with short and thickened long bones, usually found in newborns, occasionally found in the prenatal stage, and other clinical features include a series of extracutaneous manifestations, such as hypoglycemia, gastrointestinal dysfunction, immunodeficiency, anemia and increased risk of malignant tumors, etc, the specific pathogenesis is unknown.