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Hypomelanosis of Ito: a Description, Not a Diagnosis

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Hypomelanosis of Ito: a Description, Not a Diagnosis View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Hypomelanosis of Ito: A Description, Not a Diagnosis Virginia P. Sybert Childrens Hospital and Medical Center, University of Washington. Seattle, Washington, U.S.A. The term hypomelanosis ofIto has been used as a diag­ tients were mosaic for aneuploidy or unbalanced nosis for individuals with hypopigmentation or depig­ translocations, with two or more chromosomally dis­ mentation distributed along the lines of Blaschko. , tinctcell lines either within the same tissue or between Approxim,ately half of these patients have had neuro­ tissues. The more common alterations included mosaic logic, skeletal, and/or ocular abnormalities. In many, trisomy 18, diploidy/triploidy, mosaicism for sex determination that the lighter areas of skinwere hypo­ chromosome aneuploidy, and tetrasomy 12p. Karyo­ pigmented rather than the darker areas hyperpig­ typing of blood and,if necessary, skin, to detect mosai­ mented has been arbitrary. Evidence documenting cism is warranted in all patients presenting with swir­ single-gene transmission is unconvincing and recur­ ley pigmentary changes, either hyperpigmentation or rence risks appear to be negligible in most instances. hypopigmentation. The terms hypomelanosis of Ito Karyotyping of blood lymphocytes, skin fibroblasts, and incontinentia pigmenti achromians should be and/or keratinocytesoftts individuals reported inthe abandoned as they are neither diagnostic nor specific. literature revealed abnormal chromosome constitu­ Key words: ,ncontinentia pigmenti achromiam/ chromosomal tions in 60. Three patients were 46;KX/46;XY chi­ mosaicism/genetia. ] In"at Dermatol 103:141S-143S, meras, two were 46,xx/46,xx chimeras. Most pa- 1994 n 1951, MinorIto [1] described a young woman with exten­ RESULTS sive leukoderma distributed in a splash-like, swirly pattern, Chromosome Studies Of the 13 patients .recalled, cytogenetic along the lines ofBlaschko [2]. Hecoined the term incontin­ studies were possible in 12. Of these, eight were found to have entia pigmenti achromians (IPA) because the patternof color I chromosomal alterations (Table I). Six were mosaic, with two or loss was similar to that of the hyperpigmentation of incon­ more chromosomally distinct cell lines. Two patients had aneu­ tinentia pigmenti, an x-linked dominant disorder. In 1973, Jelinek ploidy without evidence for mosaicism, but only lymphocytes were [3] used the term hypomelanosis ofIto (HI) as a diagnostic appella­ studied in these two. tion for patients with hypopigmentation or depigmentation in the Including our study, cytogeneticevaluation hasbeen undertaken same pattern. More than half of the case reports of HI andIP A have in 116 of 220 individuals discussed in 77 publications (Tables 1- described a host of associated abnormalities, some of which are m). Of these, 58 (50%) were either mosaic for aneuploidy or were shared in common by many patients, others of which are distinct chromosmallyabnormal in all cells studied. In 45 patients, only one and unique. tissue was studied. Sixteen (38%) of these were aneuploid. of 70 Several modes of inheritance have been proposed, all based on instances where both blood and skin were studied, 42 individuals single case reports [4-12]. (60%) had chromosome abnormalities. In one of these, mosaicism was found only in cultured keratinocytes. Eighteen patients were MATERIALS AND METHODS mosiac or abnormal in skinonly, one was abnormal in blood only, and in Reports [13 -15] of patients with mosaicism for chromosome abnormalities 22 were abnormal both. Chromosomal alterations reported with some frequency in­ who had the skin changes of hypomelanosis of Ito promJ'ted us to initiate a recall of all of our patientswho carrieda diagnosisof HI L 16). We attempted cluded mosaicism for tetrasomy 12p (Teschler-Nicola/Killian syn­ to karyotype bothlymphocytes and fibroblasts from each. W henever possi­ drome), mosaicism for trisomy 18, diploidy/triploidy, 45,X/ ble, more than one skin biopsy was obtained, either &om each side ofthe 46,X,r(X) or 45,X/46,X, + mar and 46,XX/46,XY chimerism. body or from botha light and darkarea. At least 50 cells were examinedfrom An additional two patients, not included in the total of those each sample. In addition, I have reviewedthe English, French, Italian, and with cytogenetic abnormalities, demonstrated chimerism for two Spanish medical literature to determine the proportion of patients with normal 46,xx cell lines derived from fusion of two separate zy­ variegatepigmentation in whom cytogenetic abnormalitieswere sought and gotes. found. I have also critically reviewed all reports of transmission of HI to offspring, to assess the likelihood of single gene transmission [17]. Mendelian Transmission There have been eight purportedin­ stances of single gene inheritance of hypomelanosis of Ito. Two of these were missed diagnoses of incontinentia pigmenti [4,5,7 ]. One reportof a manwi th HI described his daughter who had a reduction Reprint requests to: Dr. Virginia P. Sybert, Children's Hospital and Medi­ defect of one leg and no pigment changes [6]. This paper hasbeen cal Center, University of Washington, Departtnents of Dermatology and r peate y demonstrating Medical Genetics,4800 SandPoint Way N .E., CH-25, Seattle, Washington e dl cited as autosomal dominant or sex­ 98105. linked dominant transmission of HI, despite the authors' explicit Abbreviations: HI, hypomelanosis of Ito; IPA, inconrinentia pigmenti statement that the daughter's defect was unrelated to HI. A three­ achromians; SF, skin fibroblasts. paragraph -long transcript of a case presented at a meeting described 0022-202X/94jS07.00 Copyright © 1994 by The Society for Investigative Dermatology, Inc. 141S 1428 SYBERT THE JOURNAL OF INVESTIGATIVE DERMATOLOGY Table I. Karyo�es of Eight Patients with noted in siblings. Two of the families were from Pakistan and Iran, Hypomelanosis 0 Ito (modified &om [15]) areas where baseline consanguinity rates are high. In such popula­ tions consanguinity does not provide compelling evidence for auto­ Sex ABe Result T"_ somal recessive inheritance [18]. Female 3 years 46,x,t(X;22)(qll.2;qI3.3) balanced.parents notmal L Female 13 months 46,xx,r(10) L CONCLUSIONS Female 21 month. 45,xx.t(15;22)/46,xx L Female Birth 45.x/46 .x. +ring L Hypomelanosis ofIto is a term that is descriptive and non-specific. It Male 18 years 47,xv.+18/46.XY L,SF Fema1e 3 years 46,xx L has been applied to individuals with diffuse, patchy, generalized, 46,xx/46,XX,de1(13)(qll) SF limited, or spotty depigmentation or hypopigmentation. It should Male 11 years 46,xv L 46,xv/ 69,xxy SF be abandoned as it continues to cause confusion. Male 15 years 46.xy L Patients presenting with hypopigmentation, depigmentation, or 46.xY/47.XY.+i(12p) SF hyperpigmentation distributed along the lines of Blaschko, or in • L.lymphoeytes;SF •• kinfibroblasts. any other patchy configuration, in the absence of a recognized diag­ nosis such as piebaldism, Waardenburg syndrome, or incontinentia pigmenti, should be karyotyped. Lymphocytes should be evaluated first, followed by fibroblast a grandfather, mother, and son with pigment loss [8]. However, the cultures of more than one skin biopsy ifthe blood is karyotypically mother's lesion involved only her leg and underwent repigmenta­ normal. If feasible, keratinocyte cultureand karyotyping may yield tion, suggestive of vitiligo. one digree presented in support of useful results. autosomal dominant inheritancet 9] was based on historical report­ Prognosis depends upon the nature of the aneuploidy. Published ing by the proband with no co E tion by examination of pur­ series of patients are not helpful in regard to the riskfor associated portedly affected relatives, in none of whom were the skin changes malformations or mental retardation as these compilations reflect described typical for HI. Three reports of isolated cases of HI within fruit salad, i.e., heterogeneity, not the many manifestations of a sibships born to consanguineous parents have been cited as proof of single entity. autosomal recessive inheritance [10-12]. No recurrences were Single-gene inheritance may be a cause in some patients with TableD. CytogeneticEvaluation Sex Result L/SF Reference M 45.xY. 14q21q)/46,xv.+t(14q21q)+mar +/ND Brai.Dtv 7:45-49. 1985 F 46,xx.+t� 2;8)(q37.2;p21.1) +/ND Neuro/35:607- 610, 1985 M 46.XY/47,xv.+18 +/+ ]Ms1 Gt:nel 20:135-137. 1983 M 46.XY/47,xv.+rmr -/+ ] CliftDysmt>rp/tDl l:2O-24. 1983 p 46,xx...,.(2;10) (L) 46,XX,ra(2;10)/47,xx.+22 (SF) +/+ A ..]Ms1Gt:nel23:739-749.198 6 P 46.XX/47,xx.+G group -/+ AM] Ms1Gt:nel 23:739-749. 1986 p 47,xx.+18 (L)46 ,xxf47,xx.+18/47,xx.+13 (SF) +/+ AM Ms116:131-136. Gt:nel 1983 F 46,xx.del(15q) mother +/ND Opl th.lmologica 200:1-6. 1990 F 46,xx.del(15q) daughter +/NO Ophlh.lmologica200 :1-6. 1990 M 46,xv/47, xv.+t -/+ Ophlh.1 Paediatr 11:273-279. 1990 F 45.x/46,xx +/ND DtvelMtd Child Neurol33:737 -743. 1991 F 46,x,+t(X;IS) +/ND PaIWrDmMtoI9:1-10. 1992 M 46,xv.9'",2q+ +/ND Pel;."n.m..IDl 9:1- 10. 1992 M 46,xv/47,xv.+t8 +/+ Clm Gt:nel 39:68-74. 1991 F 46.xx!47,xx.+t8 +/+ CIllo Gt:nel39:68-74. 1991 M 46,JCY/47,xv.+18 +/+ Am]Ms1Gtne t 35:422-424. 1990 F 46,xx/45,xx.-14/46,xx .. uclic14qf46.xx.r(14) +/+ Am] Hum Genet 45:193-20S. 1989' F 45.x(L) 4S.x/46.x,del(X) �SF ) +/+ Lancet 11:343, 1986' M 47.xYY/48.xYY.+8 (L) 48.xYY,+8 (SF) +/+ PedlalrReo 21 :294A, 1987' II 46,xx/46,xx.4p+ +/+ Pro, Gwood .... Gen et Clr 6: 105.
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