Hypomelanosis of Ito

background

Hypomelanosis of Ito (HI) syndrome is one of several ectodermal dysplasias, a group of syndromes deriving from abnormalities of the ectodermal structures, which include the hair, teeth, nails, sweat glands, cranial-facial structure, and hands. HI is a genetic condition, but it is unclear whether it may be inherited.
A distinctive feature of HI is hypopigmentation, or the lack of the pigment melanin, which gives color to the skin and hair. Hypopigmentation affects many parts of the body, and in HI it takes on a pattern known as the "lines of Blaschko." The cause of this pattern is unknown, and it does not correspond to any particular anatomical feature.
HI is marked by a lack of skin pigment on many parts of the body. The absence of pigment in skin may appear as streaks, patches, and whorls and may follow the Blaschko lines pattern. Individuals with HI may have intellectual and developmental disabilities, seizures, and other nerve disorders. Other physical characteristics of HI include a small head and problems with the skeleton, eyes, and teeth.
HI (previously known as IP type 1 or IP1) is a rare genetic disorder similar to incontinentia pigmenti (IP), which is also known as IP type 2 or IP2. However, HI has additional features, and some argue that these make HI a distinct condition. Many people describe HI as being like a negative image of IP, which is characterized by discolored skin caused by excessive deposits of melanin. In IP, melanin collects in the skin, causing wavy lines and streaks that are gray, blue, or brown.
HI is a genetic condition, but it is unclear whether it may be inherited. There are several candidate genes that may contribute to the disease, but no consensus has been reached about the genetic basis or inheritance pattern of this disease.
HI is extremely rare. It does not seem to occur in any population more frequently than another, although it affects slightly more females than males.
HI may present in many different ways in different individuals. People in whom HI symptoms are limited to the skin tend to have a normal lifespan. The severity of neurological symptoms often determines health status and quality of life. Death from HI is rare.

Related Terms

HMI, incontinentia pigmenti achromians, incontinentia pigmenti type 1 (formerly), IP1 (formerly), IPA, ITO, ITO hypomelanosis, sporadic incontinentia pigmenti.

types of the disease

A familial form of hypomelanosis of Ito (HI) syndrome exists. However, fewer than 3% of the patients have a family history of HI-type skin lesions.
There is a lack of evidence to suggest that HI always occurs through a spontaneous mutation. Some researchers suggest that the abnormalities causing HI may occur after fertilization and for unknown reasons. However, research in this area is conflicting.