What is hypomelanosis of Ito (HI)?
The definition of HI is: A neurocutaneous syndrome of streaky, patchy, whorl-like, or linear macular hypopigmentation of the skin, often associated with seizures, developmental and intellectual retardation and other anomalies.
Symptoms of HI
The symptoms of HI include:
• asymmetry of the body,
• patchy pigmentation which can occur on any part of the body, but not normally the palms, scalp or soles of the feet,
• gross motor and psychomotor retardation,
• dental and bone anomalies,
• unusual ophthalmic features,
• and kidney problems, amongst others.
Diagnosis of HI
HI is a manifestation of an etiologically heterogeneous group of disorders, some of which are associated with genetically distinct cell lines.
This is a group of disorders with the common feature of increased and/or decreased pigmentation in a characteristic formation with swirling patterns around the trunk and linear patterns down the legs and arms. Dermatologists call this pattern Blaschko's Lines. It is now known that this pattern occurs when there are two populations of cells in the skin which vary because of a chromosome problem in one set of cells or a gene change. When skin cells are cultured an abnormal chromosome pattern is found in one population of cells in about one third of affected individuals. The error seems to occur after a child is conceived. The range of effects varies widely from almost no problems (other than the skin patterning) to major developmental problems. In those with more severe effects, seizures are common. Affected individuals may have asymmetry of growth on either side of the body.
This is not an inherited disorder since the error occurs after conception in one population of cells. Reports in older literature of familial cases are unconvincing. Pigmentary mosaicism should be differentiated from the X-linked condition of Incontinentia Pigmenti where the areas of increased pigment are preceded by blistering skin lesions.
This condition is not recurrent. Management in future pregnancies should be routine, although detailed scanning may provide added reassurance.
Please note that hypomelanosis of Ito is not the same syndrome as incontinentia pigmenti (IP).
This information was developed by HITS (UK) Family Support Network and is herewith used with permission.
HITS (UK) Family Support Network. What is HI? Available at: https://www.e-fervour.com/hits/#WhatisHI. Accessed January 20, 2014.
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