Immunologic Heterogeneity in 2 Cartilage-Hair Hypoplasia Patients With a Distinct Clinical Course

Area of Science:

• Immunology
• Genetics
• Pediatrics

Background:

• Cartilage-hair hypoplasia (CHH) syndrome is a rare autosomal recessive disorder.
• CHH is characterized by skeletal dysplasia, combined immunodeficiency (CID), short stature, and increased malignancy risk.

Purpose of the Study:

• To provide clinical and immunological insights into CHH syndrome.
• To investigate two unrelated patients with clinical characteristics of CHH.

Main Methods:

• Immunological work-up including flow cytometry and immune repertoire analysis (TCR Vß, TCR-γ).
• Genetic analysis using next-generation sequencing (NGS) and Sanger sequencing.
• Analysis of T-cell receptor excision circle (TREC) levels.

Main Results:

• Patient 1 showed T-cell immunodeficiency with restricted TCR Vß and TCR-γ repertoires, and compound heterozygous RMRP variants.
• Patient 2 presented with normal TCR repertoires but had novel regulatory variants in RMRP.
• Both patients had skeletal dysplasia and varying degrees of immunodeficiency.

Conclusions:

• Immunological and genetic findings are crucial for diagnosing and managing CHH syndrome.
• Tailored diagnostics can significantly alter treatment and outcomes for CHH patients.