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 aligned according to the Blaschko lines (as a negative image of incontinentia pigmenti, Bloch-Sulzberger type). Furthermore, facultatively occurring different accompanying symptoms are associated.

The pigment disorders are based on completely different somatic mutations (translocations, trisomies, triploidies, chromosomal aberrations on chromosome 15q, among others - see also Angelman syndrome and Prader-Willi syndrome), which would not be compatible with life in the case of germline mutations. The associated extracutaneous anomalies can vary from mosaicism to mosaicism 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, swarm-like (in the Blaschko lines) depigmentations (20-40% of patients) without inflammatory or blistering preliminary stage as clinical expression of cutaneous mosaicism. Frequently combined with café-au-lait spots, also small-spotted alopecia.

In 75% of cases other concomitant diseases occur:

• Dental anomalies: palatal cusps on the incisors, enamel defects, caries, hypodontia, impaction
• CNS: macrocephaly, mental and statomotor retardation, autistic behavior, increased convulsive readiness
• Eyes: hypertelorism, strabismus, retarded development
• Hypertrophy of individual organs and body parts
• Associations with trisomy 7 have been described.

Uncharacteristic.

Nevus depigmentosus: clinical skin appearance of Blaschko-linear hypomelanosis. No extracutaneous defects.

Phylloid hyp omelanosis: Leaf-like Jugendstilornaomente. Mostly present mosaic trisomy 13q.

Incontinentia pigmenti (Bloch-Sulzberger): this systematized hypomelanosis is always preceded by an inflammatory preliminary stage.

Dermatological therapy is not usually necessary, the skin changes mainly serve to differentiate the disease from other neurological syndromes.

For cosmetic reasons, hypopigmented areas may be covered 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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