A rare genetic neurological disease characterized by progressive encephalopathy, early-onset seizures with a hypsarrhythmic pattern, facial and limb edema, severe hypotonia, early arrest of psychomotor development and craniofacial dysmorphism (evolving microcephaly, narrow forehead, short nose, prominent auricles, open mouth, micrognathia), in the absence of neuro-ophthalmic or neuroradiologic findings. Poor visual responsiveness, growth failure and tapering fingers are also associated. There is evidence the disease is caused by homozygous mutation in the CCDC88A gene on chromosome 2p16.

Pontocerebellar hypoplasia type 9 (PCH9) is an autosomal recessive neurodevelopmental and neurodegenerative disorder characterized by severely delayed psychomotor development, progressive microcephaly, spasticity, seizures, and brain abnormalities, including brain atrophy, thin corpus callosum, and delayed myelination (summary by Akizu et al., 2013). For a general phenotypic description and a discussion of genetic heterogeneity of PCH, see PCH1 (607596).

Mitochondrial complex IV deficiency nuclear type 12 (MC4DN12) is an autosomal recessive metabolic disorder characterized by the onset of neurologic dysfunction in early infancy. Affected individuals demonstrate hypotonia with poor head control, profoundly delayed global development with inability to fix and follow, poor overall growth, abnormal spasms or myoclonus, and seizures. Most patients die in the first years of life; those that survive have spastic quadriplegia, feeding difficulties necessitating tube feeding, and profoundly impaired intellectual development with poor or absent communication. More variable features include cortical blindness, nystagmus, scoliosis, and hearing impairment. Brain imaging shows abnormalities consistent with Leigh syndrome (see 256000), as well as cystic cavitation. Laboratory studies show lactic acidosis, increased serum creatine kinase, and decreased levels and activity of mitochondrial respiratory complex IV (summary by Lim et al., 2014). For a discussion of genetic heterogeneity of mitochondrial complex IV (cytochrome c oxidase) deficiency, see 220110.

CIMDAG syndrome (CIMDAG) is a multisystemic disorder characterized by severely impaired psychomotor development and hematologic abnormalities apparent from early infancy. Affected individuals show poor overall growth with microcephaly, impaired intellectual development, poor or absent speech, poor eye contact, and motor problems, such as inability to walk, hypotonia, and spasticity. Brain imaging typically shows cerebral and cerebellar atrophy, thin corpus callosum, and delayed myelination. The associated hematologic abnormalities are variable, but are mostly consistent with congenital dyserythropoietic anemia (CDA) (summary by Rodger et al., 2020 and Seu et al., 2020).

Neurodevelopmental disorder with seizures and brain abnormalities (NEDSBA) is an autosomal recessive neurologic disorder characterized by global developmental delay and onset of seizures in the first months of life associated with structural brain defects on brain imaging. Additional features may include pigmentary retinopathy with poor visual fixation and spasticity (summary by Duncan et al., 2021).