<Tr> <Th> Specialty </Th> <Td> medical genetics </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> Hoyeraal - Hreidarsson syndrome (HHS) is a very rare multisystem X-linked recessive disorder characterized by excessively short telomeres and is considered a severe form of dyskeratosis congenita . Being an X-linked disorder, HHS primarily affects males . Patients with HHS typically present in early childhood with cerebellar hypoplasia, immunodeficiency, progressive bone marrow failure, and intrauterine growth retardation . The primary cause of death in HHS is bone marrow failure, but mortality from cancer and pulmonary fibrosis is also significant . </P> <P> The currently recognized features of HHS are cerebellar hypoplasia, immunodeficiency, progressive bone marrow failure, and intrauterine growth retardation . HHS patients also commonly exhibit symptoms such as microcephaly, aplastic anemia, and mental retardation . </P>

What is dyskeratosis congenita and hoyeraal hreidarsson syndrome
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