Unilateral atrophy of facial tissues, including muscles, bones and skin.

Brown-Vialetto-Van Laere syndrome is a rare autosomal recessive neurologic disorder characterized by sensorineural hearing loss and a variety of cranial nerve palsies, usually involving the motor components of the seventh and ninth to twelfth (more rarely the third, fifth, and sixth) cranial nerves. Spinal motor nerves and, less commonly, upper motor neurons are sometimes affected, giving a picture resembling amyotrophic lateral sclerosis (ALS; 105400). The onset of the disease is usually in the second decade, but earlier and later onset have been reported. Hearing loss tends to precede the onset of neurologic signs, mostly progressive muscle weakness causing respiratory compromise. However, patients with very early onset may present with bulbar palsy and may not develop hearing loss until later. The symptoms, severity, and disease duration are variable (summary by Green et al., 2010). Genetic Heterogeneity of Brown-Vialetto-Van Laere Syndrome See also BVVLS2 (614707), caused by mutation in the SLC52A2 gene (607882) on chromosome 8q.

Congenital myasthenic syndromes (CMS) are a group of inherited disorders affecting the neuromuscular junction (NMJ). Patients present clinically with onset of variable muscle weakness between infancy and adulthood. These disorders have been classified according to the location of the defect: presynaptic, synaptic, and postsynaptic. CMS10 is an autosomal recessive CMS resulting from a postsynaptic defect affecting endplate maintenance of the NMJ. Patients present with limb-girdle weakness in the first decade. Treatment with ephedrine or salbutamol may be beneficial; cholinesterase inhibitors should be avoided (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462).

SH3TC2-related hereditary motor and sensory neuropathy (SH3TC2-HMSN) is a demyelinating neuropathy characterized by severe spine deformities (scoliosis or kyphoscoliosis) and foot deformities (pes cavus, pes planus, or pes valgus) that typically present in the first decade of life or early adolescence. Other findings can include cranial nerve involvement (most commonly tongue involvement, facial weakness/paralysis, hearing impairment, dysarthria) and respiratory problems.

Amyotrophic lateral sclerosis-12 with or without frontotemporal dementia (ALS12) is a neurodegenerative disorder characterized by onset of ALS in adulthood. Rare patients may also develop frontotemporal dementia (FTD). Autosomal dominant and autosomal recessive inheritance patterns have been reported; there is also sporadic occurrence (summary by Maruyama et al., 2010 and Feng et al., 2019). For a general phenotypic description and a discussion of genetic heterogeneity of amyotrophic lateral sclerosis, see ALS1 (105400).

Spinocerebellar ataxia-36 (SCA36) is a slowly progressive neurodegenerative disorder characterized by adult-onset gait ataxia, eye movement abnormalities, tongue fasciculations, and variable upper motor neuron signs. Some affected individuals may develop hearing loss (summary by Garcia-Murias et al., 2012). For a general discussion of autosomal dominant spinocerebellar ataxia, see SCA1 (164400).

EXOSC3 pontocerebellar hypoplasia (EXOSC3-PCH) is characterized by abnormalities in the posterior fossa and degeneration of the anterior horn cells. At birth, skeletal muscle weakness manifests as hypotonia (sometimes with congenital joint contractures) and poor feeding. In persons with prolonged survival, spasticity, dystonia, and seizures become evident. Within the first year of life respiratory insufficiency and swallowing difficulties are common. Intellectual disability is severe. Life expectancy ranges from a few weeks to adolescence. To date, 82 individuals (from 58 families) with EXOSC3-PCH have been described.

This autosomal recessive form of distal arthrogryposis, designated DA5D by McMillin et al. (2013), is characterized by severe camptodactyly of the hands, including adducted thumbs and wrists; mild camptodactyly of the toes; clubfoot and/or a calcaneovalgus deformity; extension contractures of the knee; unilateral ptosis or ptosis that is more severe on one side; a round-shaped face; arched eyebrows; a bulbous, upturned nose; and micrognathia. Notably, these patients do not have ophthalmoplegia. For a general phenotypic description and discussion of genetic heterogeneity of distal arthrogryposis, see DA1A (108120). For discussion of genetic heterogeneity of distal arthrogryposis type 5, see DA5 (108145).

Charcot-Marie-Tooth disease type 2S is a relatively pure form of autosomal recessive axonal neuropathy characterized by onset in the first decade of slowly progressive distal muscle weakness and atrophy affecting the lower and upper limbs. Patients have decreased reflexes and variable distal sensory impairment (summary by Cottenie et al., 2014). For a phenotypic description and a discussion of genetic heterogeneity of axonal CMT, see CMT2A1 (118210).

Congenital myasthenic syndrome associated with AChR deficiency is a disorder of the postsynaptic neuromuscular junction (NMJ) clinically characterized by early-onset muscle weakness with variable severity. Electrophysiologic studies show low amplitude of the miniature endplate potential (MEPP) and current (MEPC) resulting from deficiency of AChR at the endplate. Patients may show a favorable response to amifampridine (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462).

Myofibrillar myopathy-7 (MFM7) is an autosomal recessive muscle disorder characterized by early childhood onset of slowly progressive muscle weakness that primarily affects the lower limbs and is associated with joint contractures (summary by Straussberg et al., 2016). For a general phenotypic description and a discussion of genetic heterogeneity of myofibrillar myopathy, see MFM1 (601419).

Facioscapulohumeral muscular dystrophy (FSHD) typically presents with weakness of the facial muscles, the stabilizers of the scapula, or the dorsiflexors of the foot. Severity is highly variable. Weakness is slowly progressive and approximately 20% of affected individuals eventually require a wheelchair. Life expectancy is not shortened.

Juvenile amyotrophic lateral sclerosis-27 (ALS27) is an autosomal dominant disorder characterized by early childhood-onset lower extremity spasticity manifesting as toe walking and gait abnormalities, followed by progressive lower motor neuron-mediated weakness without sensory signs or symptoms (Mohassel et al., 2021). For a discussion of genetic heterogeneity of amyotrophic lateral sclerosis, see ALS1 (105400).