Hoyeraal–Hreidasson syndrome[2] is a very rare multisystem X-linked recessive disorder characterized by excessively short telomeres and is considered a severe form of dyskeratosis congenita.

Patients typically present in early childhood with cerebellar hypoplasia, immunodeficiency, progressive bone marrow failure, and intrauterine growth restriction.

[4][5][6] The currently recognized features are cerebellar hypoplasia, immunodeficiency, progressive bone marrow failure, and intrauterine growth restriction.

[3] Patients with Hoyeraal–Hreidasson syndrome frequently present with the mucocutaneous triad of nail dysplasia, lacy skin pigmentation, and oral leukoplakia.

[citation needed] Although the pathogenesis remains unknown, it is strongly suspected that the clinical sequelae of Hoyeraal–Hreidasson syndrome arise from the accelerated telomere shortening.