Incontinentia Pigmenti (IP), historically called Bloch-Sulzberger syndrome, is a rare inherited disorder that affects tissues derived from the embryonic ectoderm — the skin, hair, teeth, and nails — and also the eyes and the central nervous system. It is a genodermatosis: a genetic condition whose most visible sign is on the skin, but whose most consequential effects can lie elsewhere.

IP is uncommon. Public health birth-defect registries estimate a birth prevalence on the order of 0.6 to 1.2 per 100,000, and more than 2,000 affected females have been described in the medical literature. It occurs almost exclusively in females; affected males are rare and, when they do occur, usually carry an extra X chromosome (47,XXY) or have the variant in only a fraction of their cells (mosaicism). The reasons for this striking sex skew are genetic, and are explained in the next section.

The hallmark of IP is a skin pattern that evolves through four stages and follows the lines of Blaschko — invisible developmental lines that trace the migration of skin cells in the embryo, producing the characteristic streaks, whorls, and "marble-cake" swirls. Those same lines are echoed in the faint motif behind this page.

The single most important idea for any family new to IP is this: IP is highly variable. Two people with the very same genetic variant — even sisters — can be affected to very different degrees. Most individuals with IP have a normal life span and normal intelligence, with the condition centered on skin and dental findings. A minority face vision-threatening eye disease or neurological complications. Because the most serious risks are treatable when caught early, structured surveillance — especially of the eyes in infancy — is the practical heart of good care.

The gene and the protein

IP is caused by loss-of-function variants in IKBKG, a gene on the long arm of the X chromosome (Xq28). The gene was formerly known as NEMO (NF-κB Essential Modulator), and that older name describes its job well. The NEMO protein is a required component of a cellular machine that switches on NF-κB, a master regulator of inflammation and — critically — of cell survival.

When NEMO is absent or broken, cells lose an important brake on programmed cell death and become vulnerable to self-destruction in response to ordinary inflammatory signals. The blistering, inflammatory skin of early IP is, in essence, this process playing out visibly: cells carrying the faulty gene are selectively lost.

How the variant works on the X chromosome

About 80–90% of cases are caused by one recurrent change — a deletion of roughly 11.7 kilobases that removes exons 4 through 10 of the gene. It arises because the region is flanked by repeated sequences that predispose it to faulty recombination. The remaining cases are caused by smaller sequence changes (a well-known example is c.1167dup).

Because females have two X chromosomes, every cell randomly silences one of them early in development — a process called X-inactivation. A girl with IP is therefore a mosaic: some cells use the healthy X, others the faulty one. The body progressively favors cells with the working gene, and the pattern of which cells survive where is what produces the swirled, Blaschko-line skin pattern — and the wide variability between individuals.

Why IP is so rare in males

A male has only one X chromosome. A boy who inherits an IKBKG loss-of-function variant has no healthy copy to fall back on — every cell is affected. This is generally lethal before birth, so affected male pregnancies typically end in miscarriage. This single fact explains both the female predominance of IP and the pattern of recurrent male pregnancy loss seen in affected families. It is central to the reproductive section that follows.

The rare males who do live with IP fall into two groups: those with a 47,XXY karyotype (the extra normal X provides the rescue that females have), and those with somatic mosaicism, in whom the variant arose after conception and is present in only some cells.

The skin — four evolving stages

The skin findings of IP are the basis of diagnosis. They classically pass through four stages, though stages may overlap, not everyone shows every stage, and lesions follow the lines of Blaschko while usually sparing the face.

The eyes — the highest priority in infancy

Eye involvement is the most vision-threatening aspect of IP. The retina can develop an abnormal blood-vessel pattern — areas that fail to develop normal circulation, followed by fragile new vessel growth (neovascularization), similar to retinopathy of prematurity. Left undetected, this can progress to retinal detachment and permanent vision loss, sometimes within the first months or years of life. Other findings include strabismus (eye misalignment) and changes at the fovea. Because this process is treatable with laser or cryotherapy when caught early, scheduled dilated retinal examinations from the newborn period onward are the single most important intervention in IP care. See the surveillance schedule in section 05.

Teeth, hair, and nails

Dental findings are common and often lifelong: missing teeth (hypodontia), small teeth (microdontia), conical or peg-shaped teeth, and delayed eruption — affecting both baby and adult teeth. Hair changes include patchy hair loss (often at the crown) and wiry, woolly hair. Nails may show ridging, pitting, or dystrophy. These are generally managed cosmetically or with dental prosthetics, and rarely affect health directly — though dental issues can affect chewing and speech and deserve early attention.

The nervous system

A minority of individuals with IP have neurological involvement, but when present it is among the most serious aspects of the condition. The spectrum includes seizures (neonatal seizures are a particularly important warning sign and a marker of poorer outlook), and in some infants a stroke-like or inflammatory injury to the brain in the first days of life. A subset of children have developmental delay, intellectual disability, or motor problems such as spasticity. Brain MRI may show changes in the white matter or evidence of small-vessel injury. Most children with IP, it should be stressed, are neurologically typical.

How the diagnosis is made

Diagnosis rests on major criteria — the staged skin lesions — and minor criteria that support it: the dental, hair, nail, and retinal findings, and a family history consistent with X-linked inheritance or multiple miscarriages. When the clinical picture is uncertain, molecular testing of IKBKG confirms it — using the pseudogene-aware methods described in section 02.

Recurrence risk — the inheritance arithmetic

A woman with IP carries one IKBKG variant on one of her two X chromosomes. At every conception, there is a 50% chance she passes on the X with the variant. Combined with the sex of the child, that produces four equally likely outcomes at conception — but, because of male lethality, the picture among live-born children is different. The visualizer below shows both. Toggle between them.

Two consequences follow directly from this arithmetic. First, a woman with IP has an elevated rate of miscarriage, because roughly one in four conceptions is an affected male that is usually lost early — and IP is, for this reason, an under-recognized cause of recurrent male pregnancy loss. Second, a daughter who inherits the variant will herself have IP and will face these same considerations when she reaches her own family-planning years; a son who inherits the healthy X is unaffected and does not carry it forward.

Before pregnancy — preconception planning

The most useful single step a family can take is also the earliest: identify the exact IKBKG variant in the family by molecular testing, performed by a laboratory using pseudogene-aware methods. Almost every reproductive option below depends on knowing precisely what to test for. A consultation with a certified genetic counselor — ideally before conception — is where the recurrence numbers, the miscarriage risk, and the options are translated into a plan that fits the family's values.

Reproductive options

There is no single "right" path; the options below are presented as a menu to discuss with a genetics and maternal-fetal medicine team.

• Natural conception, with or without prenatal diagnosis. Many families conceive naturally and decide separately whether to pursue testing during the pregnancy.
• Preimplantation genetic testing for a monogenic condition (PGT-M). Through IVF, embryos are created and biopsied, and only embryos that do not carry the familial IKBKG variant are selected for transfer. Recent advances are notable here: long-read-sequencing approaches now make PGT-M feasible even when no other affected family members are available for testing, and despite the pseudogene problem (see highlighted research below).
• Prenatal diagnosis in an established pregnancy. Chorionic villus sampling (CVS, roughly 10–13 weeks) or amniocentesis (roughly 15–20 weeks) can test the fetus for the familial variant. Determining fetal sex is itself informative, given male lethality.
• Donor gametes or adoption. Counseling also covers these paths for families who prefer them.

During pregnancy — what monitoring looks like

For a pregnant woman who herself has IP, the pregnancy is generally managed in the usual way; IP in the mother does not, by itself, make a pregnancy high-risk for her. The attention turns to the fetus. Ultrasound can show clues to an affected male fetus — increased nuchal translucency, cystic hygroma, and, in more severe cases, non-immune hydrops fetalis (abnormal fluid accumulation). Recurrent, otherwise-unexplained male hydrops or fetal loss in a woman with even subtle skin, hair, or dental signs should prompt an evaluation for IP — a point made forcefully by recent research below. Care is best coordinated with a maternal-fetal medicine specialist, with delivery planned at a center that has neonatology and pediatric ophthalmology available.

Childbirth and the newborn period

IP itself does not dictate the route of delivery — that is decided on ordinary obstetric grounds. What matters most is preparing the newborn team in advance:

• A newborn with IP often shows Stage I blistering at or soon after birth. This can closely mimic infection (such as herpes or bullous impetigo). The team should know IP is expected, so the skin is handled gently and not over-treated — while still appropriately ruling out true infection.
• The blistering skin is not contagious. Care is gentle handling, keeping lesions clean, and preventing secondary infection.
• A baseline dilated retinal examination by a pediatric ophthalmologist should be arranged in the first weeks of life, because retinal disease can progress quickly. This is the single most time-sensitive priority.
• Any seizure activity in the newborn period warrants prompt neurology evaluation.
• The multidisciplinary team — genetics, dermatology, ophthalmology, neurology, and dentistry — is best assembled early rather than after problems appear.

Highlighted research on reproduction in IP

According to PubMed — recent peer-reviewed work directly relevant to this section. The Living Research Feed in section 06 keeps an up-to-date list automatically.

Care by system

The ophthalmology surveillance schedule

The eye-examination schedule below reflects the surveillance recommendations summarized in GeneReviews. Because retinal disease in IP can move fast in infancy, the early exams are frequent and then space out with age. Enter a date of birth to generate a concrete, dated schedule you can take to appointments. Your ophthalmologist sets the actual schedule — findings on any exam may prompt more frequent monitoring.