Cartilage-hair hypoplasia (CHH) is an autosomal recessive metaphyseal chondrodysplasia caused by mutations in the RMRP gene encoding the RNA component of a mitochondrial ribonuclease complex. CHH is particularly prevalent among the Old Order Amish and the Finns. CHH is characterized by severe short-limbed short stature, sparse hair, defective immunity involving both cellular and humoral components, and defective erytropoiesis. Cancer incidence is 7-fold higher in patients with CHH as compared with the normal population. Especially non-Hodgkin lymphoma and basal cell carcinoma are frequent. Patients with CHH need close follow-up also in adulthood.