VPS13A disease, caused by VPS13A loss-of-function pathogenic variants, is characterized by a spectrum of movement disorders (chorea, dystonia, tics, sometimes parkinsonism); predominant orofacial choreic and dystonic movements and tics (with involuntary tongue protrusion on attempted swallowing, habitual tongue and lip biting resulting in self-mutilation, involuntary vocalizations); dysarthria and dysphagia; psychiatric, cognitive, and behavioral changes ("frontal lobe type"); seizures; and progressive neuromuscular involvement. Huntingtonism (triad of progressive movement disorder and cognitive and behavioral alterations) is a typical presentation. Phenotypic variability is considerable even within the same family, including for monozygotic twins. Mean age of onset is about 30 years. VPS13A disease runs a chronic progressive course and may lead to major disability within a few years. Some affected individuals are bedridden or wheelchair dependent by the third decade. Age at death ranges from 28 to 61 years; several instances of sudden unexplained death or death during epileptic seizures have been reported.

CODAS is an acronym for cerebral, ocular, dental, auricular, and skeletal anomalies. CODAS syndrome is a rare disorder characterized by a distinctive constellation of features that includes developmental delay, craniofacial anomalies, cataracts, ptosis, median nasal groove, delayed tooth eruption, hearing loss, short stature, delayed epiphyseal ossification, metaphyseal hip dysplasia, and vertebral coronal clefts (summary by Strauss et al., 2015).

A rare Huntington disease-like syndrome with characteristics of childhood-onset progressive neurologic deterioration with pyramidal and extrapyramidal abnormalities, chorea, dystonia, ataxia, gait instability, spasticity, seizures, mutism, and (on brain MRI) progressive frontal cortical atrophy and bilateral caudate atrophy.

Asparagine synthetase deficiency (ASD) mainly presents as a triad of congenital microcephaly, severe developmental delay, and axial hypotonia followed by spastic quadriplegia. Low cerebrospinal fluid (CSF) asparagine level can help the clinician in differentiating this disorder from others. In most cases age of onset of apnea, excessive irritability, and seizures is soon after birth. Affected individuals typically do not acquire any developmental milestones. Spastic quadriplegia can lead to severe contractures of the limbs and neurogenic scoliosis. Feeding difficulties (gastroesophageal reflux disease, frequent vomiting, swallowing dysfunction, and gastroesophageal incoordination) are a significant problem in most affected individuals. A majority have cortical blindness. MRI findings are nonspecific but may include generalized atrophy and simplified gyral pattern.

Amyotrophic lateral sclerosis-24 (ALS24) is a fatal neurodegenerative disease characterized by adult-onset loss of motor neurons (Brenner et al., 2016).

Polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) is characterized by fractures (resulting from radiologically demonstrable polycystic osseous lesions), frontal lobe syndrome, and progressive presenile dementia beginning in the fourth decade. The clinical course of PLOSL can be divided into four stages: 1.. The latent stage is characterized by normal early development. 2.. The osseous stage (3rd decade of life) is characterized by pain and tenderness, mostly in ankles and feet, usually following strain or injury. Fractures are typically diagnosed several years later, most commonly in the bones of the extremities. 3.. In the early neurologic stage (4th decade of life), a change of personality begins to develop insidiously. Affected individuals show a frontal lobe syndrome (loss of judgment, euphoria, loss of social inhibitions, disturbance of concentration, and lack of insight, libido, and motor persistence) leading to serious social issues. 4.. The late neurologic stage is characterized by progressive dementia and loss of mobility. Death usually occurs before age 50 years.

Polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy-2 (PLOSL2), or Nasu-Hakola disease, is a recessively inherited presenile frontal dementia with leukoencephalopathy and basal ganglia calcification. In most cases the disorder first manifests in early adulthood as pain and swelling in ankles and feet, followed by bone fractures. Neurologic symptoms manifest in the fourth decade of life as a frontal lobe syndrome with loss of judgment, euphoria, and disinhibition. Progressive decline in other cognitive domains begins to develop at about the same time. The disorder culminates in a profound dementia and death by age 50 years (summary by Klunemann et al., 2005). For a discussion of genetic heterogeneity of polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy, see 221770.