Hypomelanosis itoQ82.3

Ito 1952

Ito syndrome, also known as Blaschko-linear hypomelanosis, is not a nosological entity. It comprises a group of different, congenital (or developing in early childhood) neurocutaneous phenotypes (pigment mosaics) which are based on striped (systematized) hypopigmentation of the skin, which are oriented according to the Blaschko lines (as a negative image of incontinentia pigmenti, type Bloch-Sulzberger). Furthermore, facultatively occurring different accompanying symptoms are associated.

The dyspigmentations are based on completely different somatic mutations (translocations, trisomies, triploidies, aberrations of chromosomes among others on chromosome 15q - see also Angelman syndrome and Prader-Willi syndrome.), which would not be compatible with life in case of germ mutations. The associated extracutaneous anomalies can vary from mosaic to mosaic so that an exact clinical clarification is necessary.

Unclear mode of inheritance and chromosomal mosaic pattern on the Genloci 9q33-qter, 15q11-q13 and Xp11, among others

• Integument: Reticular or patchy, linear, swarmlike depigmentations (20-40% of the patients) without inflammatory or blistery preliminary stage as cutaneous expression of a mosaicism. Frequently also café-au-lait stains; small stained alopecia.
• In 75% of the cases other concomitant diseases occur:
  • Dental anomalies: palatal cusps on the incisors, enamel defects, caries, hypodontia, impaction
  • CNS: macrocephaly, mental and statomotor retardation, autistic behaviour, increased propensity to cramps
  • eyes: hypertelorism, strabismus, retarded development
  • Hypertrophy of individual organs and body parts
• Connections with trisomy 7 are described.

Uncharacteristic.

Naevus depigmentosus: clinical skin appearance of the Blaschko-lineraen hypomelanosis. No extracutaneous defects.

Phylloid hypomelanosis: foliar art nouveau moments. Mostly present mosaic trisomy 13q.

Incontinentia pigmenti (Bloch-Sulzberger): this systematized hypomelanosis is always preceded by a preliminary stage of inflammation.

• Dermatological therapy is usually not necessary, the skin changes mainly serve to differentiate the disease from other neurological syndromes.
• For cosmetic reasons it may be necessary to cover hypopigmented areas with camouflage (e.g. Dermacolor). Treatment of neurological changes by neurologists.

Trisomy 7, which in some cases of hypomelanosis Ito has been demonstrated, is not only found in hypomelanotic but also in hypermelanotic mosaicisms. For example in LWH (Linear Whorled Hypermelanosis). This proves that hypomelanosis Ito and "Linear Whorled Hypermelanosis" have a common genetic basis.

The term "Incontinentia pigmenti achromians", which is based on the term Incontinentia pig menti, should not be used because the two diseases have no pathogenetic similarities.

Provided that there are no extracutaneous defects, the hypomelanoses following the Blaschko lines are called naevus depigmentosus or naevus achromicus.

1. Böhm M (2015) Differential diagnosis of hypomelanosis. dermatologist 66: 945-958
2. Garcia Muret MP et al (2002) Hypomelanosis of Ito with Sturge-Weber syndrome-like leptomeningeal angiomatosis. Pediatric Dermatol 19: 536-540
3. Garcia Muret MP et al (2002) Hypomelanosis of Ito with Sturge-Weber syndrome-like leptomeningeal angiomatosis. Pediatric Dermatol 19: 536-540
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9. Stratigos AJ et al (2003) Lasers and aesthetic dermatology. Dermatologist 54: 603-613