Hypomelanosis of Ito: A Description, Not a Diagnosis.

Abstract

The term hypomelanosis of Ito has been used as a diagnosis for individuals with hypopigmentation or depigmentation distributed along the lines of Blaschko. Approximately half of these patients have had neurologic, skeletal, and/or ocular abnormalities. In many, determination that the lighter areas of skin were hypopigmented rather than the darker areas hyperpigmented has been arbitrary. Evidence documenting single-gene transmission is unconvincing and recurrence risks appear to be negligible in most instances. Karyotyping of blood lymphocytes, skin fibroblasts, and/or keratinocytes of 115 individuals reported in the literature revealed abnormal chromosome constitutions in 60. Three patients were 46,XX/46,XY chimeras, two were 46XX/46,XX chimeras. Most patients were mosaic for aneuploidy or unbalanced translocations, with two or more chromosomally distinct cell lines either within the same tissue or between tissues. The more common alterations included mosaic trisomy 18, diploidy/triploidy, mosaicism for sex chromosome aneuploidy, and tetrasomy 12p. Karyotyping of blood and, if necessary, skin, to detect mosaicism is warranted in all patients presenting with swirley pigmentary changes, either hyperpigmentation or hypopigmentation. The terms hypomelanosis of Ito and incontinentia pigmenti achromians should be abandoned as they are neither diagnostic or specific.

Total Hemi-overgrowth in Pigmentary Mosaicism of the (Hypomelanosis of) Ito Type

“…The skin patterns may appear as an isolated skin disorder (a pure cutaneous trait) ( pigmentary mosaicism or linear hypomelanosis [ of the Ito type ]) 2–4,7 or as a complex malformation syndrome in association with extracutaneous manifestations, 5,6,8 including central nervous system or musculoskeletal alterations ( hypomelanosis of Ito [HI]). 5,6,8,11–16 More rarely, the eyes, heart, and genital organs can also be involved.…”

Network analyses of differentially expressed proteins in amniotic fluid supernatant associated with abnormal human karyotypes

“…Although dysfunctional pigmentation of the skin is not a common feature of ES, this association has been reported (33). Sybert (34) also found that 60 of the 115 individuals with hypomelanosis were found to have chromosomal alterations, among which mosaic trisomy 18 was the common abnormal karyotype. Collectively, these reports suggest that detection of chromosomal anomalies, including mosaicism, is warranted in patients presenting with skin depigmentation.…”

Chimaerism, Mosaicism, and Forensic DNA Analysis

“…A true human chimaera represents a phenotype which would potentially give a confounding result when analyzed for forensic purposes. Of the true chimaeras in the literature there are a number of possible identifying features, including ambiguous genitalia and hermaphroditism (1,23), as well as patchy skin or eye pigmentation (24). Of course this isn't necessarily the case as true chimaeras can be normal in appearance without any distinct markings to set them apart, as was shown in a case involving a maternity dispute.…”