Microhydranencephaly (MHAC) is a severe abnormality of brain development characterized by both

microcephaly Microcephaly (from New Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it ...

and

hydranencephaly Hydranencephaly is a condition in which the brain's cerebral hemispheres are absent to a great degree and the remaining cranial cavity is filled with cerebrospinal fluid. "Cephalic" is the scientific term for "head" or "head end of body". Hydrane ...

. Signs and symptoms may include severe microcephaly, scalp

rugae In anatomy, rugae are a series of ridges produced by folding of the wall of an organ. Most commonly rugae refers to the gastric rugae of the internal surface of the stomach. Function A purpose of the gastric rugae is to allow for expansion o ...

(a series of ridges), and profound

intellectual disability Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signif ...

. Familial occurrence of the condition is very rare but it has been reported in a few families. It has been suggested that some cases MHAC are inherited in an

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and ...

manner via a

loss-of-function mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosi ...

of the gene ''

NDE1 Nuclear distribution protein nudE homolog 1 is a protein that in humans is encoded by the ''NDE1'' gene. Clinical significance Mutations In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, v ...

''.

Notable cases

Jaxon Buell Jaxon Emmett Buell (August 27, 2014 – April 1, 2020) was an American child known for being born missing about 80% of his brain due to microhydranencephaly. He surpassed doctors' expectations, who predicted he would not live to be one year old. ...

was born on August 27, 2014 with 80% of his brain, and most of his skull, missing. He surpassed all doctors' expectations, who did not expect him to live to his second birthday. He died at five years old.

References

Rare diseases Congenital disorders of nervous system {{genetic-disorder-stub