Incontinentia Pigmenti Not All That Rare


STANFORD, CALIF. — A rare genetic disorder that usually is lethal to male babies and can leave abnormalities of the skin, eyes, and other body parts in females, may be more common than originally thought.

Incontinentia pigmenti is caused by a mutation in the IKBKG gene (also known as NEMO), which resides on the X chromosome. A genetic diagnosis can be helpful in females with suspected incontinentia pigmenti because they carry a 50:50 risk of passing the mutation on to their offspring, Dr. Louanne Hudgins said at a pediatric update sponsored by Stanford University.

Typically, blistering on the skin of a neonate or infant progresses to a wart-like rash, swirling macular hyperpigmentation, and linear hypopigmentation.

Other ectodermal-derived tissues are affected, too. Patients with incontinentia pigmenti often have patchy alopecia of the scalp, dystrophic nails, and tooth abnormalities (fewer teeth than normal or abnormal tooth formation, such as a cone-shaped tooth). Associated eye problems are the most significant finding in survivors with incontinentia pigmenti. They often have retinal vascular proliferation, which can lead to retinal detachment.

"The mother may look completely normal or may have linear patches without as much hair" as a typical scalp, but genetic testing can identify incontinentia pigmenti in 80% of cases, said Dr. Hudgins, professor of pediatrics and chief of medical genetics at Stanford.

She and her associates used to test for incontinentia pigmenti only in girls who had all of the associated findings, and rarely made the diagnosis. More recently, however, "we've been doing the testing in kids with a few findings, and are finding the mutation. I think it's more common than we thought it was," she said. "In our genetic disorders of the skin clinic, we see as many as four or five cases per year" of incontinentia pigmenti.

Even with a presumptive diagnosis, it's important to order an ophthalmologic exam. "If this child is at risk for retinal detachment, you need to have that child followed by ophthalmology on a regular basis so you can maintain the best vision possible," she said. Dental and dermatologic evaluations also are warranted. "If they have ongoing skin problems, it's certainly a good idea to have a dermatologist follow them," said Dr. Hudgins, who reported having no conflicts of interest.

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