Ichthyosis vulgaris is converted to filaggrin which plays a vital role in the structure of the skin). Around 10% of the population have some detrimental mutations to the profilaggrin gene that is also linked to atopic dermatitis (another skin disorder that is often present with ichthyosis vulgaris). The exact mutation is only known for some cases of ichthyosis vulgaris. It is generally considered to be an autosomal dominant condition, i.e., a single genetic mutation causes the disease and an affected person has a 50% chance of passing the condition on to their child. There is some research indicating it may be semi-dominant.
Ichthyosis hystrix though some experts believe that it may have been a type of epidermolytic hyperkeratosis. From the history of the Lambert family the disease appears to have been an autosomal dominant condition. HID syndrome is also known as ichthyosis hystrix, Rheydt type after the German city of Rheydt near Düsseldorf where it was first discovered. Symptoms are bilateral hearing loss and spiky hyperkeratotic masses which cover the whole body though the palms and soles are less badly affected. It can be differentiated from KID syndrome which also has symptoms of deafness and ichthyosis by the different distribution of hyperkeratosis. It is