Von Hippel-Lindau (VHL) syndrome is characterized by hemangioblastomas of the brain, spinal cord, and retina; renal cysts and clear cell renal cell carcinoma; pheochromocytoma, pancreatic cysts, and neuroendocrine tumors; endolymphatic sac tumors; and epididymal and broad ligament cysts. Cerebellar hemangioblastomas may be associated with headache, vomiting, gait disturbances, or ataxia. Spinal hemangioblastomas and related syrinx usually present with pain. Sensory and motor loss may develop with cord compression. Retinal hemangioblastomas may be the initial manifestation of VHL syndrome and can cause vision loss. Renal cell carcinoma occurs in about 70% of individuals with VHL and is the leading cause of mortality. Pheochromocytomas can be asymptomatic but may cause sustained or episodic hypertension. Pancreatic lesions often remain asymptomatic and rarely cause endocrine or exocrine insufficiency. Endolymphatic sac tumors can cause hearing loss of varying severity, which can be a presenting symptom. Cystadenomas of the epididymis are relatively common. They rarely cause problems, unless bilateral, in which case they may result in infertility.

Meniere disease is a chronic illness characterized by intermittent episodes of vertigo lasting from minutes to hours, with fluctuating sensorineural hearing loss, tinnitus, and aural pressure (Sajjadi and Paparella, 2008).

Neurofibromatosis 2 (NF2) is characterized by bilateral vestibular schwannomas with associated symptoms of tinnitus, hearing loss, and balance dysfunction. The average age of onset is 18 to 24 years. Almost all affected individuals develop bilateral vestibular schwannomas by age 30 years. Affected individuals may also develop schwannomas of other cranial and peripheral nerves, meningiomas, ependymomas, and, very rarely, astrocytomas. Because NF2 is considered an adult-onset disease, it may be underrecognized in children, in whom skin tumors and ocular findings (retinal hamartoma, thickened optic nerves, cortical wedge cataracts, third cranial nerve palsy) may be the first manifestations. Mononeuropathy that occurs in childhood is an increasingly recognized finding; it frequently presents as a persistent facial palsy or hand/foot drop.

MFN2 hereditary motor and sensory neuropathy (MFN2-HMSN) is a classic axonal peripheral sensorimotor neuropathy, inherited in either an autosomal dominant (AD) manner (~90%) or an autosomal recessive (AR) manner (~10%). MFN2-HMSN is characterized by more severe involvement of the lower extremities than the upper extremities, distal upper-extremity involvement as the neuropathy progresses, more prominent motor deficits than sensory deficits, and normal (>42 m/s) or only slightly decreased nerve conduction velocities (NCVs). Postural tremor is common. Median onset is age 12 years in the AD form and age eight years in the AR form. The prevalence of optic atrophy is approximately 7% in the AD form and approximately 20% in the AR form.

Arnold-Chiari type I malformation refers to a relatively mild degree of herniation of the posteroinferior region of the cerebellum (the cerebellar tonsils) into the cervical canal with little or no displacement of the fourth ventricle. It is characterized by one or both pointed (not rounded) cerebellar tonsils that project 5 mm below the foramen magnum, measured by a line drawn from the basion to the opisthion (McRae Line)

Episodic ataxia is a genetically heterogeneous neurologic condition characterized by spells of incoordination and imbalance, often associated with progressive ataxia. Episodic ataxia type 2 is the most common form of EA (Jen et al., 2007). For a discussion of genetic heterogeneity of episodic ataxia, see EA1 (160120).

DFNA9 is an autosomal dominant adult-onset form of progressive sensorineural hearing loss associated with variable vestibular dysfunction (summary by Robertson et al., 2006).

Hyperostosis cranialis interna is a bone disorder characterized by endosteal hyperostosis and osteosclerosis of the calvaria and the skull base. The progressive bone overgrowth causes entrapment and dysfunction of cranial nerves I, II, V, VII, and VIII (Waterval et al., 2010).

An autosomal dominant nonsyndromic deafness that has material basis in variation in the chromosome region 2p12.

Autosomal dominant deafness-41 (DFNA41) is characterized by onset of progressive sensorineural hearing loss usually in the second decade. The hearing loss is severe and ultimately affects all frequencies. Exposure to noise exacerbates the hearing loss, particularly at high frequencies (summary by Yan et al., 2013).

Any autosomal dominant nonsyndromic deafness in which the cause of the disease is a mutation in the CCDC50 gene.

X-linked deafness-5 is a neurologic disorder characterized by childhood onset of auditory neuropathy and later onset of distal sensory impairment affecting the peripheral nervous system (summary by Zong et al., 2015).

An autosomal dominant condition caused by mutations in the TMC1 gene, encoding transmembrane channel-like protein 1. It is characterized by bilateral progressive hearing loss.

A very rare form of hereditary episodic ataxia with characteristics of vestibular ataxia, vertigo, tinnitus and interictal myokymia.

A very rare form of hereditary episodic ataxia with characteristics of late-onset episodic ataxia, recurrent attacks of vertigo and diplopia.

An autosomal dominant nonsyndromic deafness that has material basis in variation in the chromosome region 2q23-q24.3.

DFNA2 nonsyndromic hearing loss is characterized by symmetric, predominantly high-frequency sensorineural hearing loss (SNHL) that is progressive across all frequencies. At younger ages, hearing loss tends to be mild in the low frequencies and moderate in the high frequencies; in older persons, the hearing loss is moderate in the low frequencies and severe to profound in the high frequencies. Although the hearing impairment is often detected during routine hearing assessment of a school-age child, it is likely that hearing is impaired from birth, especially at high frequencies. Most affected persons initially require hearing aids to assist with sound amplification between ages ten and 40 years. By age 70 years, all persons with DFNA2 nonsyndromic hearing loss have severe-to-profound hearing impairment.

Any autosomal recessive nonsyndromic deafness in which the cause of the disease is a mutation in the LOXHD1 gene.

Any autosomal dominant nonsyndromic deafness in which the cause of the disease is a mutation in the DIABLO gene.

Lipodystrophies are rare disorders characterized by loss of body fat from various regions and predisposition to metabolic complications of insulin resistance and lipid abnormalities. FPLD7 is an autosomal dominant disorder with a highly variable phenotype. Additional features, including early-onset cataracts and later onset of spasticity of the lower limbs, have been noted in some patients (summary by Garg et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660.

An autosomal dominant nonsyndromic deafness that has material basis in variation in the chromosome region 13q34.

Y-linked deafness-1 (DFNY1) is characterized by male-limited postlingual progressive sensorineural hearing loss of variable severity, with onset in the first to third decades of life (Wang et al., 2009). Genetic Heterogeneity of Y-Linked Deafness DFNY2 (400047) is caused by mutation in the TBL1Y gene (400033).

Autosomal dominant deafness-50 is a form of nonsyndromic hearing loss. Hearing impairment shows postlingual onset and is progressive (summary by Mencia et al., 2009).

Autosomal dominant deafness-58 (DFNA58) is characterized by postlingual sensorineural deafness, with tinnitus and vestibular dysfunction additionally present in some patients (summary by Lezirovitz et al., 2020).

DFNA67 is a form of nonsyndromic sensorineural hearing loss. Onset ranges from the first to the fourth year of life. Hearing loss initially affects high frequencies, with variable progression. There are no vestibular symptoms (Xing et al., 2015; Thoenes et al., 2015).

Autosomal dominant deafness-77 (DFNA77) is characterized by progressive hearing loss affecting high frequencies beginning in the second to third decades of life and affecting all frequencies by the fourth or fifth decades (Li et al., 2019).

Autosomal dominant deafness-82 (DFNA82) is characterized by onset of rapidly progressive bilateral sensorineural hearing loss usually early in the first decade, although later onset may rarely occur. Affected individuals often pass the newborn screening test before the onset of mild to profound hearing loss (Smits et al., 2019).

Autosomal dominant deafness-86 (DFNA86) is characterized by late-onset progressive hearing loss through p53 (TP53; 191170)-mediated hair cell apoptosis (Zhang et al., 2020).