Atrophoderma vermiculata, a form of keratosis pilaris atrophicans, typically presents in childhood with erythema and follicular keratotic papules that slowly progress to characteristic atrophy, which has been described as worm-eaten, reticular, or honeycomb, and occurs on the cheeks, preauricular area, and forehead. More rarely, the atrophy may extend to the upper lip, helices, ear lobes, and, in some cases, the limbs. The degree of inflammation, the presence of milia, and the extent of follicular plugs are variable (summary by Luria and Conologue, 2009).

A rare primary bone dysplasia characterized by severe mesomelic shortness particularly of the lower limbs with distinctive triangular or rhomboid-shaped tibiae and fibulae, accompanied by bony protuberances and skin dimples. Additional manifestations include radioulnar synostosis, dislocation of the radial head, abnormalities of the hands (such as oligosyndactyly or fusiform-shaped fingers) and feet (pes equinovarus, synostoses of tarsals/metatarsals and phalanges), and dysmorphic facial features.

Aromatic L-amino acid decarboxylase deficiency (AADCD) is an autosomal recessive inborn error in neurotransmitter metabolism that leads to combined serotonin and catecholamine deficiency (Abeling et al., 2000). The disorder is clinically characterized by vegetative symptoms, oculogyric crises, dystonia, and severe neurologic dysfunction, usually beginning in infancy or childhood (summary by Brun et al., 2010).

A rare disorder characterised by tetralogy of Fallot, minor facial anomalies, and severe intellectual deficiency and growth delay. Dysmorphic features include large, protruding, abnormally modelled ears and broad nasal root. Microcephaly and syndactyly of second and third toes have also been recorded. All patients have severe intellectual deficiency. The condition is transmitted as an autosomal recessive trait.

A rare syndrome described in two sisters of Mennonite descent, with characteristics of sparse hair, osteopenia, intellectual disability, minor facial abnormalities, joint laxity and hypotonia. There have been no further descriptions in the literature since 1992.

Laurin-Sandrow syndrome (LSS) is an autosomal dominant disorder characterized by polysyndactyly of hands and feet, mirror image duplication of feet, and nasal defects (hypoplastic alae nasi, short columella), in connection with absent patella and duplicated fibula (summary by Lohan et al., 2014).

ALS2-related disorder involves retrograde degeneration of the upper motor neurons of the pyramidal tracts and comprises a clinical continuum of the following three phenotypes: Infantile ascending hereditary spastic paraplegia (IAHSP), characterized by onset of spasticity with increased reflexes and sustained clonus of the lower limbs within the first two years of life, progressive weakness and spasticity of the upper limbs by age seven to eight years, and wheelchair dependence in the second decade with progression toward severe spastic tetraparesis and a pseudobulbar syndrome caused by progressive cranial nerve involvement. Juvenile primary lateral sclerosis (JPLS), characterized by upper motor neuron findings of pseudobulbar palsy and spastic quadriplegia without dementia or cerebellar, extrapyramidal, or sensory signs. Juvenile amyotrophic lateral sclerosis (JALS or ALS2), characterized by onset between ages three and 20 years. All affected individuals show a spastic pseudobulbar syndrome (spasticity of speech and swallowing) together with spastic paraplegia. Some individuals are bedridden by age 12 to 50 years.

Multiple congenital anomalies-hypotonia-seizures syndrome-2 (MCAHS2) is an X-linked recessive neurodevelopmental disorder characterized by dysmorphic features, neonatal hypotonia, early-onset myoclonic seizures, and variable congenital anomalies involving the central nervous, cardiac, and urinary systems. Some affected individuals die in infancy (summary by Johnston et al., 2012). The phenotype shows clinical variability with regard to severity and extraneurologic features. However, most patients present in infancy with early-onset epileptic encephalopathy associated with developmental arrest and subsequent severe neurologic disability; these features are consistent with a form of developmental and epileptic encephalopathy (DEE) (summary by Belet et al., 2014, Kato et al., 2014). The disorder is caused by a defect in glycosylphosphatidylinositol (GPI) biosynthesis. For a discussion of genetic heterogeneity of MCAHS, see MCAHS1 (614080). For a discussion of nomenclature and genetic heterogeneity of DEE, see 308350. For a discussion of genetic heterogeneity of GPI biosynthesis defects, see GPIBD1 (610293).