Mutations in BCS1L can result in a variety of phenotypes, one of which is the Bjornstad Syndrome (BS).


Key phenotypic features of Bjornstad Syndrome - both of the following:

(1) congenital sensorineural hearing loss

(2) pili torti, with twisted and brittle hair. A hair shaft is flattened at irregular intervals and twisted 180 degrees from the normal axis


Some patients may have additional findings suggesting a mild complex III deficiency:

(1) growth retardation

(2) developmental delay

(3) profound hypotonia


The patients do not display the multisystem organ dysfunction seen with other syndromes with mutations in BCS1L.


Inheritance: autosomal recessive


Chromosome location: 2q34-36.


Gene: BCS1L

Gene product: a mitochondrial inner-membrane protein that is a member of the AAA family of ATPases. It acts as a chaperone protein in the assembly of mitochondrial respiratory chain complex III.


The mutations in patients with Bjornstad Syndrome affect protein-protein interactions without altering ATP-binding residues.


In classic BS increased amounts of reactive oxygen species are generated by complex I within mitochondria, resulting in oxidative stress to structures such as the hair follicle and inner ear.


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