Hypomelanosis of Ito: Description, Causes and Risk Factors:
A rare genodermatosis characterized by hyperpigmented lesions in linear, zebra stripe, and other bizarre configurations following the lines of Blaschko; occasionally accompanied by other developmental anomalies of the eyes, teeth, nails, skeleton, nails, heart. Although its prevalence is unknown, more than 700 cases have been reported in the world literature up-to-date. Most cases have been described in white persons, although other races are affected as well. The occurrence of hypomelanosis of Ito in male patient is unusual with a worldwide total of 28 cases found so far.
The dermatologic features involve four stages: stage I is characterized by erythema, vesicles, and pustules; stage II by papules, verrucous lesions, and hyperkeratosis; stage III by hyperpigmentation; and stage IV by pallor, atrophy, and scarring.
The cause of hypomelanosis of Ito has been traced to a defective gene on the X chromosome called NEMO. The gene is also known as IKK-gamma or IKBKG, which is its "official" gene name. It is involved in a cellular process known as "signal transduction" where signals from outside the cell are transmitted to the nucleus of the cell to alter gene expression. The NEMO gene is of less than average size, spanning about 23 thousand base pairs. The NEMO gene produces a protein that is essential for cells, and defects in it result in hypomelanosis of Ito. Males cannot survive without a functioning NEMO gene, and thus die in utero. In females, some cells have a normal functioning NEMO gene (from the normal X chromosome) while other cells have a defective NEMO gene. Currently, it is thought that the symptoms of hypomelanosis of Ito in females result from cells with a defective NEMO gene in the affected tissue. Now that the gene has been found, this view can be tested. In about 85% of families, the mutation in the NEMO gene that results in hypomelanosis of Ito is identical, even though the families are unrelated. A portion of the NEMO gene is duplicated, and these duplicated parts can result in deletions that disrupt the NEMO gene's function. This is unusual in human genetic disorders (most of the time, the mutations are different in different families). The presence of a frequent mutation, however, allows for easier testing.
It seems that there is a genetic background in the pathogenesis of this syndrome. About 50% of the hypomelanosis of Ito cases have positive family history. There must be X-linked dominant trait that is usually lethal in males. More than 95% of the reported cases are females the few males affected being probably result of spontaneous mutations. These mutations are suspected to produce a failure of immune tolerance in ectodermal tissues, resulting in an autoimmune-like reaction in heterozygote girls and a fetal graft versus host like disease in homozygous boys.
The prognosis is generally good and depends on extracutaneous manifestations. There is a poor prognosis and developmental delay is patients with seizures during the first weeks of life. Absence of seizures and normal developmental milestones appear to predict a good prognosis. Intensity of skin manifestation and eosinophil count are not related to more severe visceral involvement and have no prognostic value.
Most newborns with hypomelanosis of Itowill develop discolored skin within the first two weeks. The pigmentation involves the trunk and extremities, is slate-grey, blue or brown, and is distributed in irregular marbled or wavy lines. The discoloration fades with age. Neurological problems
include loss of brain tissue (known as cerebral atrophy), the formation of small cavities in the central white matter of the brain, and the loss of neurons in the cerebellar cortex
. About 20% of children with hypomelanosis of Itowill have slow motor development, muscle weakness in one or both sides of the body, mental retardation, and seizures. They are also likely to have visual problems, including crossed eyes, cataracts, and severe visual loss. Dental problems are also common, including missing or peg-shaped teeth.
The doctor will perform a physical exam, look at the eyes, and test muscle movement.There may be unusual patterns and blisters on the skin, as well as bone abnormalities. An eye exam may reveal cataracts, strabismus (crossed eyes), or other problems.The diagnosis of hypomelanosis of Itois established by clinical findings and occasionally by corroborative skin biopsy. Molecular genetic testing of the NEMO IKBKG gene (chromosomal locus Xq28) reveals disease-causing mutations in about 80% of probands. Such testing is available clinically.
The inflammatory lesions particularly if denuded should be treated with standard wound care to avoid secondary infections. Spontaneous improvement and resolution of skin lesions is the general rule. The use of lasers in the treatment of hyperpigmentation should be discouraged because it has been reported to trigger an extensive vesiculobullous eruption. Concerning the teeth, referral for Radiologic evaluation and dental intervention by the age of 2 years is appropriate.
Regular visits to a pediatric ophthalmologist or retinal specialist familiar with retinopathy of prematurity (ROP) are essential during the first year of life. A complete Neurologic examination is warranted for all infants with newly diagnosed hypomelanosis of Ito. Neonatal seizures are an important prognostic indicator and may predict developmental in later childhood or adolescence but are generally easy to control with appropriate anticonvulsant therapy and usually do not result in other impairment of the CNS or mental retardation if late in onset. Therefore, parents should be reassured of good prognosis if Neurologic deficits do not develop during pregnancy.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.