MedGen

Brittle cornea syndrome (BCS) is characterized by blue sclerae, corneal rupture after minor trauma, keratoconus or keratoglobus, hyperelasticity of the skin, and hypermobility of the joints (Al-Hussain et al., 2004). It is classified as a form of Ehlers-Danlos syndrome (Malfait et al., 2017). Genetic Heterogeneity of Brittle Cornea Syndrome Brittle cornea syndrome-2 (BCS2; 614170) is caused by mutation in the PRDM5 gene (614161) on chromosome 4q27. [from OMIM]

Any retinitis pigmentosa in which the cause of the disease is a mutation in the PDE6B gene. [from MONDO]

The overlapping phenotypes of neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD) represent the milder manifestations of the Zellweger syndrome spectrum (ZSS) of peroxisome biogenesis disorders. The clinical course of patients with the NALD and IRD presentation is variable and may include developmental delay, hypotonia, liver dysfunction, sensorineural hearing loss, retinal dystrophy, and visual impairment. Children with the NALD presentation may reach their teens, and those with the IRD presentation may reach adulthood. Some patients with PEX10 mutations have a milder disorder characterized by childhood-onset cerebellar ataxia and neuropathy without mental retardation (summary by Waterham and Ebberink, 2012). For a complete phenotypic description and a discussion of genetic heterogeneity of PBD(NALD/IRD), see 601539. Individuals with mutations in the PEX10 gene have cells of complementation group 7 (CG7, equivalent to CGB). For information on the history of PBD complementation groups, see 214100. [from OMIM]

Neuronal ceroid lipofuscinosis-6B (CLN6B) is an autosomal recessive form of 'Kufs disease,' which refers in general to adult-onset neuronal ceroid lipofuscinosis without retinal involvement. CLN6B is a neurodegenerative disorder with a mean onset of symptoms at around age 28 years, although onset in the teens and later adulthood may also occur. Patients typically present with progressive myoclonus epilepsy, ataxia, loss of motor function, dysarthria, progressive dementia, and progressive cerebral and cerebellar atrophy on brain imaging. Ultrastructural examination typically shows fingerprint profiles and granular osmiophilic deposits in some tissues, including brain samples (summary by Arsov et al., 2011 and Berkovic et al., 2019). However, pathologic findings in peripheral tissues in adults is not as accurate for diagnosis as it is in children with the disease (Cherian et al., 2021). For a general phenotypic description and a discussion of genetic heterogeneity of CLN, see CLN1 (256730). [from OMIM]

Hereditary motor and sensory neuropathy type VIB is an autosomal recessive complex progressive neurologic disorder characterized mainly by early-onset optic atrophy resulting in progressive visual loss and peripheral axonal sensorimotor neuropathy with highly variable age at onset and severity. Affected individuals may also have cerebellar or pontocerebellar atrophy on brain imaging, and they may show abnormal movements such as ataxia, dysmetria, and myoclonus (summary by Abrams et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of HMSN6, see HMSN6A (601152). [from OMIM]

Any congenital stationary night blindness in which the cause of the disease is a mutation in the PDE6B gene. [from MONDO]

SCN1A seizure disorders encompass a spectrum that ranges from simple febrile seizures and generalized epilepsy with febrile seizures plus (GEFS+) at the mild end to Dravet syndrome and intractable childhood epilepsy with generalized tonic-clonic seizures (ICE-GTC) at the severe end. Phenotypes with intractable seizures including Dravet syndrome are often associated with cognitive decline. Less commonly observed phenotypes include myoclonic astatic epilepsy (MAE), Lennox-Gastaut syndrome, infantile spasms, epilepsy with focal seizures, and vaccine-related encephalopathy and seizures. The phenotype of SCN1A seizure disorders can vary even within the same family. [from GeneReviews]

A rare, hereditary connective tissue disease characterized by severe ocular manifestations due to extreme corneal thinning and fragility with rupture in the absence of significant trauma, often leading to irreversible blindness. Extraocular manifestations comprise deafness, developmental hip dysplasia, and joint hypermobility. [from ORDO]

Spondyloepimetaphyseal dysplasia with joint laxity-3 (SEMDJL3) is characterized by multiple joint dislocations at birth, severe joint laxity, scoliosis, gracile metacarpals and metatarsals, delayed bone age, and poorly ossified carpal and tarsal bones (Girisha et al., 2016). For a discussion of genetic heterogeneity of SEMD with joint laxity, see SEMDJL1 (271640). [from OMIM]

HHV-6 encephalitis refers to inflammation of the brain due to an infection with human herpesvirus 6. People who have undergone allogeneic hematopoietic cell transplantation are at an increased risk for developing HHV-6 encephalitis, particularly when umbilical cord blood stem cells are used. People with immune system disorders may also be at an increased risk for developing this infection. Signs and symptoms vary, but often include confusion, anterograde amnesia (difficulty learning new information following the onset of amnesia), short-term memory loss, and seizures.Diagnosis often involves lumbar puncture, virus testing, and MRI. EEG 's may also be recommendedwhen seizures are suspected. HHV-6 encephalitis is treated with an antiviral agent with activity against HHV-6. Long term outlook (chance of full recovery) can vary considerably depending individual patient factors. [from MONDO]