At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. [ncbi.nlm.nih.gov]

Showing of 33 80%-99% of people have these symptoms Cerebellar vermis hypoplasia 0001320 Death in infancy Infantile death Lethal in infancy [ more ] 0001522 Feeding difficulties Feeding problems Poor feeding [ more ] 0011968 Irritability Irritable 0000737 [rarediseases.info.nih.gov]

They may also have an unusually small lower jaw and chin (micrognathia) and an enlarged liver (hepatomegaly). Affected infants may have seizures and difficulty maintaining their body temperature. [ghr.nlm.nih.gov]

[…] have these symptoms Cleft soft palate 0000185 Decreased fetal movement Less than 10 fetal movements in 12 hours 0001558 Decreased skull ossification Decreased bone formation of skull 0004331 Generalized tonic-clonic seizures Grand mal seizures 0002069 Hepatomegaly [rarediseases.info.nih.gov]

Mild hepatomegaly has been observed in several affected individuals, usually during acute illnesses associated with metabolic acidosis. 2-ketoglutaric acidosis has been demonstrated in a number of Amish infants with this disorder (a variable finding). [ncbi.nlm.nih.gov]

Myopathic facies Generalized muscle weakness Muscular dystrophy Ventriculomegaly Strabismus Epileptic encephalopathy Progressive neurologic deterioration Hepatic failure Elevated hepatic transaminase Respiratory failure Hypoplasia of the corpus callosum Hepatomegaly [mendelian.co]

0001376 Percent of people who have these symptoms is not available through HPO Autosomal recessive inheritance 0000007 Cerebellar hypoplasia Small cerebellum Underdeveloped cerebellum [ more ] 0001321 Congenital onset Symptoms present at birth 0003577 Flexion [rarediseases.info.nih.gov]

Limited joint mobility Limited joint motion [ more ] 0001376 Percent of people who have these symptoms is not available through HPO Autosomal recessive inheritance 0000007 Cerebellar hypoplasia Small cerebellum Underdeveloped cerebellum [ more ] 0001321 [rarediseases.info.nih.gov]

Showing of 33 80%-99% of people have these symptoms Cerebellar vermis hypoplasia 0001320 Death in infancy Infantile death Lethal in infancy [ more ] 0001522 Feeding difficulties Feeding problems Poor feeding [ more ] 0011968 Irritability Irritable 0000737 [rarediseases.info.nih.gov]

The single affected individual described by Siu et al [2010] had irritability and profound developmental delay. The Amish patients were able to breast/bottle feed early on, but developed severe irritability and seizures. [ncbi.nlm.nih.gov]

Often they become very irritable starting in the second or third month of life. [ghr.nlm.nih.gov]

Case studies report that the infant has seizures early on, is cold all the time, becomes irritable at ages 12 - 16 weeks, and dies before the age of one year. [owlcation.com]

Physical therapy may alleviate contractures or other secondary neurologic manifestations. Infectious illnesses are managed to minimize acidosis. GENETIC COUNSELING: Amish lethal microcephaly is inherited in an autosomal recessive manner. [ncbi.nlm.nih.gov]

Troyer Syndrome - progressive spastic paraparesis (lower limb paralysis), dysarthria (leads to difficulty in speaking), and pseudobulbar palsy (inability to control facial movements); distal amyotrophy (muscle atrophy); motor and cognitive developmental [owlcation.com]