MedGen

Cataracts, hearing impairment, nephrotic syndrome, and enterocolitis-2 (CHINE2) is an autosomal recessive syndromic disorder characterized by onset of this constellation of features in infancy, resulting in death in early childhood. Telomeres are shortened, but classic mucocutaneous features of DKCB1 are not typically observed. CHINE2 is due to a ribosomal pseudouridylation defect (Balogh et al., 2020). See also CHINE1 (301108), caused by mutation in the DKC1 gene (300126). [from OMIM]

Telomere-related pulmonary fibrosis and/or bone marrow failure syndrome-9 (PFBMFT9) is an autosomal dominant short telomere syndrome characterized by the development of pulmonary fibrosis or hematologic abnormalities, including leukopenia and leukemia, in adulthood. Liver disease may also be present. There is incomplete penetrance and evidence of genetic anticipation. Affected individuals have shortened telomeres, but do not show mucocutaneous manifestations (Kannengiesser et al., 2020). For a discussion of genetic heterogeneity of telomere-related pulmonary fibrosis and/or bone marrow failure, see PFBMFT1 (614742). [from OMIM]

Dyskeratosis congenita and related telomere biology disorders (DC/TBD) are caused by impaired telomere maintenance resulting in short or very short telomeres. The phenotypic spectrum of telomere biology disorders is broad and includes individuals with classic dyskeratosis congenita (DC) as well as those with very short telomeres and an isolated physical finding. Classic DC is characterized by a triad of dysplastic nails, lacy reticular pigmentation of the upper chest and/or neck, and oral leukoplakia, although this may not be present in all individuals. People with DC/TBD are at increased risk for progressive bone marrow failure (BMF), myelodysplastic syndrome or acute myelogenous leukemia, solid tumors (usually squamous cell carcinoma of the head/neck or anogenital cancer), and pulmonary fibrosis. Other findings can include eye abnormalities (epiphora, blepharitis, sparse eyelashes, ectropion, entropion, trichiasis), taurodontism, liver disease, gastrointestinal telangiectasias, and avascular necrosis of the hips or shoulders. Although most persons with DC/TBD have normal psychomotor development and normal neurologic function, significant developmental delay is present in both forms; additional findings include cerebellar hypoplasia (Hoyeraal Hreidarsson syndrome) and bilateral exudative retinopathy and intracranial calcifications (Revesz syndrome and Coats plus syndrome). Onset and progression of manifestations of DC/TBD vary: at the mild end of the spectrum are those who have only minimal physical findings with normal bone marrow function, and at the severe end are those who have the diagnostic triad and early-onset BMF. [from GeneReviews]