Cartilage hair hypoplasia: Heterogeneity in clinical features and management among siblings

Abstract

Background: Cartilage-hair hypoplasia (CHH), caused by mutations in the ribonuclease mitochondrial RNA-processing (RMRP) gene, is associated with diverse immune abnormalities including combined immune deficiency (CID). Most patients with CHH are managed with supportive measurements, while few have received allogeneic hematopoietic stem cell transplantations (HSCT). The progression of the immune abnormalities and the impact of HSCT in patients with CHH and CID have not been well characterized. Methods: The clinical and laboratory findings of 2 siblings diagnosed in infancy with CHH and CID due to the common 70A>G mutation in RMRP, including the effects of HSCT performed in 1 of them, were compared. Results: Both patients suffered from recurrent respiratory infections at early age with reduced T cells numbers and responses. Patient 1 immune function continued to deteriorate leading to HSCT from an HLA-matched sibling at 4.5 years of age. The patient suffered acute and chronic graft versus host disease of the skin with residual mild joint contractures and scleroderma-like skin changes. Seven years after HSCT patient 1 has normal immune function. Immune evaluations of patient 2 in the first years of life indicated mild improvement. The patient did not have a suitable related HSCT donor and the family elected to continue with supportive care. At 7 years of age, patient 2 is clinically well and thriving with persistent T cell abnormalities. Conclusions: Close monitoring of immune function in early life for patients with CHH and CID as well as the availability of suitable donors assists in determining management, including HSCT. Statement of novelty: The manuscript demonstrates the importance of close monitoring and personalized approach in the management of patients affected by CHH.