Cartilage-hair hypoplasia in a patient with compound heterozygous variants in the RMRP gene: A case report.

RATIONALE: 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.

PATIENT CONCERNS: The case of a 1.5-year-old male patient with severe short stature (height 70 cm, <-3 SD), sparse scalp hair, and short limbs, without ligamentous laxity or anemia.

DIAGNOSES: Family-based whole-exome sequencing revealed compound heterozygous variants in RMRP: NR_003051.3: n.-21_-9dup and n.5C > T. Classified as pathogenic or likely pathogenic according to ACMG guidelines, these variants confirm the diagnosis of CHH.

INTERVENTIONS: Due to the elevated tumor predisposition associated with CHH, and because growth hormone therapy is currently contraindicated, no disease-specific interventions have been initiated.

OUTCOMES: We have confirmed that the child has been diagnosed with CHH, but no intervention has been given, and we will do further follow-up and look forward to finding a treatment for the disease.

LESSONS: This report describes a rare case of RMRP-associated CHH. This case broadens the clinical understanding of the RMRP mutational spectrum and phenotypic variability, providing new insights into genotype-phenotype correlations in RMRP-associated disorders. We were currently unable to take effective treatment measures for this child, and we hope that in the future, there will be treatments such as gene therapy to bring hope to children and their families.