Cartilage-hair hypoplasia

Cartilage-hair hypoplasia is a rare genetic disorder first reported by Victor McKusick in 1965. It is caused by mutations in RMRP, a gene on chromosome 9 that produces a non-coding RNA component of an enzyme called RNase MRP, and it is inherited in an autosomal recessive pattern. The condition produces short-limbed dwarfism from skeletal dysplasia, unusually fine and light hair and eyebrows, hyperextensible joints in the hands and feet, and spine abnormalities. Immune function is variably affected, ranging from mild lymphopenia to combined immunodeficiency with defective antibody and cell-mediated immunity, and some patients face an increased risk of cancer as a result. A study of 108 Finnish patients documented this range of immune involvement in detail. No verified treatment for the underlying disorder has yet been discovered; care addresses individual symptoms and complications as they arise.