Dyschromatosis universalis hereditaria.

Reticulate pigmentary dyschromatoses primarily include dyschromatosis universalis hereditaria (DUH), dyschromatosis symmetrica hereditaria (DSH) (Reticulate acropigmentation of Dohi), and unilateral dermatomal pigmentary dermatosis, which differ in their patterns of distribution. The disease was initially described by Ichikawa and Hiraga in Germany in 1933. The prevalence of DUH is 0.3 per 100,000 with a female preponderance. The skin lesions usually appear in infancy or early childhood and cease to progress beyond adolescence. The subtypes DUH 1 and DUH 3 are found to have autosomal dominant inheritance, which is the most common inheritance pattern, while DUH 2 has an autosomal recessive pattern. The most common gene involved in DUH is ABCB6, while the other genes include SASH 1, PER 3, and KITLG (DUH type 2). DUH is characterized by multiple irregular hyperpigmented macules interspersed with hypopigmented macules in a mottled pattern over the trunk and extremities. The face is involved in 50% of individuals. Rarely, it can also involve hairs, nails, mucous membranes, palms, and soles. Other varied presentations include localized forms, localization of lesions to sun-exposed areas, large macules, uniform palmar hypopigmentation, diffuse hyperpigmentation with spotty depigmented macules, and unilateral involvement. DUH has been reported to be associated with various cutaneous and systemic diseases. The authors have observed cases of DUH associated with hepatocellular carcinoma, solitary keratoacanthoma, and dermoid cyst. The various diagnostic modalities include dermoscopy, histopathology, electron microscopy, and targeted gene sequencing. Though various treatment modalities like NBUVB and lasers have been tried, no treatment is promising.

Laser-assisted drug delivery of synthetic alpha melanocyte stimulating hormone and L-tyrosine leads to increased pigmentation area and expression of melanogenesis genes in a porcine hypertrophic scar model.

OBJECTIVES: One symptom of hypertrophic scar (HTS) that can develop after burn injury is dyschromia with hyper- and hypopigmentation. There are limited treatments for these conditions. Previously, we showed there is no expression of alpha melanocyte stimulating hormone (α-MSH) in hypopigmented scars, and if these melanocytes are treated with synthetic α-MSH in vitro, they respond by repigmenting. The current study tested the same hypothesis in the in vivo environment using laser-assisted drug delivery (LADD). METHODS: HTSs were created in red Duroc pigs. At Day 77 (pre), they were treated with CO2 fractional ablative laser (FLSR). Synthetic α-MSH was delivered as a topical solution dissolved in  l-tyrosine (n = 6, treated). Control scars received LADD of  l-tyrosine only (n = 2, control). Scars were treated and examined weekly through Week 4. Digital images and punch biopsies of hyper, hypo-, and normally pigmented scar and skin were collected. Digital pictures were analyzed with ImageJ by tracing the area of hyperpigmentation. Epidermal sheets were obtained from punch biopsies through dispase separation and RNA was isolated. qRT-PCR was run for melanogenesis-related genes: tyrosinase (TYR), tyrosinase-related protein-1 (TYRP1), and dopachrome tautomerase (DCT). Two-way ANOVA with multiple comparisons and Dunnett's correction compared the groups. RESULTS: The areas of hyperpigmentation were variable before treatment. Therefore, data is represented as fold-change where each scar was normalized to its own pre value. Within the LADD of NDP α-MSH + l-tyrosine group, hyperpigmented areas gradually increased each week, reaching 1.3-fold over pre by Week 4. At each timepoint, area of hyperpigmentation was greater in the treated versus the control (1.04 ± 0.05 vs. 0.89 ± 0.08, 1.21 ± 0.07 vs. 0.98 ± 0.24, 1.21 ± 0.08 vs. 1.04 ± 0.11, 1.28 ± 0.11 vs. 0.94 ± 0.25; fold-change from pre-). Within the treatment group, pretreatment, levels of TYR were decreased -17.76 ± 4.52 below the level of normal skin in hypopigmented scars. After 1 treatment, potentially due to laser fractionation, the levels decreased to -43.49 ± 5.52. After 2, 3, and 4 treatments, there was ever increasing levels of TYR to almost the level of normally pigmented skin (-35.74 ± 15.72, -23.25 ± 6.80, -5.52 ± 2.22 [p < 0.01, Week 4]). This pattern was also observed for TYRP1 (pre = -12.94 ± 1.82, Week 1 = -48.85 ± 13.25 [p < 0.01], Weeks 2, 3, and 4 = -34.45 ± 14.64, -28.19 ± 4.98, -6.93 ± 3.05 [p < 0.01, Week 4]) and DCT (pre = -214.95 ± 89.42, Week 1 = -487.93 ± 126.32 [p < 0.05], Weeks 2, 3, and 4 = -219.06 ± 79.33, -72.91 ± 20.45 [p < 0.001], -76.00 ± 24.26 [p < 0.001]). Similar patterns were observed for scars treated with LADD of  l-tyrosine alone without NDP α-MSH. For each gene, in hyperpigmented scar, levels increased at Week 4 of treatment compared to Week 1 (p < 0.01). CONCLUSIONS: A clinically-relevant FLSR treatment method can be combined with topical delivery of synthetic α-MSH and l-tyrosine to increase the area of pigmentation and expression of melanogenesis genes in hypopigmented HTS. LADD of  l-tyrosine alone leads to increased expression of melanogenesis genes. Future studies will aim to optimize drug delivery, timing, and dosing.

The PER3rs772027021 SNP induces pigmentation phenotypes of dyschromatosis universalis hereditaria.

Dyschromatosis universalis hereditaria (DUH) is a pigmentary genodermatosis characterized by a mixture of hyperpigmented and hypopigmented macules distributed randomly over the body. Although Sterile Alpha motif- and SH3 domain-containing protein 1 (SASH1) and ATP-binding cassette subfamily B, member 6 (ABCB6) have been identified as causative genes for this disorder, some cases involve unknown pathogenic genes. In this study, whole-exome sequencing, data analysis, and Sanger sequencing were utilized for a four-generation extended Chinese family with DUH. A single-nucleotide polymorphism (SNP) (c. 517C > T (p.P173S), rs772027021) variant in exon 5 of Period Circadian Regulator 3 (PER3) (NM_001289861) was detected in each affected individual of the DUH family; the c. 517C > T SNP of PER3 (PER3rs772027021 SNP) and a novel mutation in exon 14 of SASH1 (c. 1574C > G (p.T525R)) were both found in the proband. The affected individuals carrying PER3rs772027021 SNP in this family demonstrated mild-pigmented phenotypes compared to those of the proband carrying PER3rs772027021 SNP and SASH1 T525R mutation. Increased melanin synthesis was induced by PER3rs772027021 SNP in the melanocytes of affected epithelial tissues. Mutated SASH1 or PER3rs772027021 SNP alone or cooperation of mutation of SASH1 and PER3rs772027021 SNP synergistically led to increased melanin synthesis and enhanced proliferation of melanoma cells in vitro. We also phenotypically characterized a commercially available zebrafish mutant line harboring the PER3rs772027021 SNP to induce melanocyte proliferation in vivo. Our results are the first to reveal that this PER3 SNP may be pathogenic for a novel DUH subtype with mild hyperpigmented and/or hypopigmented phenotypes and that mutation of SASH1 and PER3 cooperatively promotes hyperpigmentation phenotypes. KEY MESSAGES: PER3 rs772027021 SNP is identified to be associated with hyperpigmentation and/or hypopigmentation phenotype and the novel pathogenic variant of PER3 rs772027021 SNP probably contributed the pathogenesis of DUH. SASH1T525R mutation is confirmed to associate with DUH. A novel autosomal dominant inheritance DUH subtype with mild pigmentated phenotypes is caused by the PER3rs772027021 SNP.

Chinese Pedigree with Hereditary Gastrointestinal Stromal Tumors: A Case Report and Literature Review.

Familial gastrointestinal stromal tumor (GIST) is a rare autosomal dominant genetic disorder with only a few affected families reported to date. Here, we report a case of familial GISTs harboring a novel germline mutation within exon 18 of KIT. A 58-year-old male patient presented with gastric subepithelial lesions accompanied by cutaneous hyperpigmentation, which were subsequently diagnosed as multinodular GISTs. Endoscopic surgery was initially conducted to remove the larger lesions, and pathological examinations were then conducted for the diagnosis of GISTs. Family history revealed that some other family members had similar cutaneous pigmentations. Whole-exome sequencing was used to search for potential driver mutations, and Sanger sequencing was used for mutation validation. A novel primary driver mutation of KIT (c.G2485C, p.A829P) was detected in these hereditary GISTs, which has been reported in some targeted chemotherapy-resistant GISTs. Cell models were subsequently established for the rapid screening of candidate drugs and exploring potential mechanisms. This mutation could lead to cell proliferation and imatinib resistance by ligand-independent activation of KIT; however, ripretinib administration was identified as an applicable targeted therapy for this mutation. The mutation activated the JAK/STAT3 and MAPK/ERK pathways, which could be inhibited by ripretinib administration. To the best of our knowledge, this is the first report of the KIT-A829P mutation in familial GISTs, complementing the pathogenesis of familial GISTs and providing valuable information for the precision treatment of this disease.

Happle-Tinschert syndrome variable phenotype as part of the mosaic hedgehog spectrum: Report of three cases.

Happle-Tinschert syndrome is a rare genodermatosis caused by a postzygotic mutation in SMO gene. The most recognized clinical findings include segmentally arranged basaloid follicular hamartomas, nevoid hypertrichosis, linear atrophoderma, and hypopigmentation or hyperpigmentation following Blaschko lines associated with osseous, dental, and cerebral alterations. We report three additional cases, two of which lacked the pathognomonic basaloid follicular hamartomas, with genetic confirmation and detailed clinical characterization and describe new cutaneous features of this infrequent syndrome.

Diagnosis, treatment and genetic analysis of a case of skin hyperpigmentation as the only manifestation with X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (X-ALD) is an inherited disease caused by a mutation in the adenosine 5'-triphosphate binding cassette subfamily D member 1 (ABCD1) gene encoding a peroxisomal transmembrane protein, which has various clinical manifestations and a rapid progression from initial symptoms to fatal inflammatory demyelination. Therefore, identification of early clinical symptoms and further early diagnosis as well as treatment can effectively prevent disease development. In this study, we reported the laboratory and radiographic features in a rare case of X-ALD with 3-year skin hyperpigmentation as the only manifestation. And the ABCD1 gene was sequenced for the patient and his parents by a high-throughput sequencing method. The results of laboratory examination showed adrenocortical hypofunction and increased serum concentrations of very long-chain fatty acids. Brain MRI showed no obvious abnormal signal shadow. A hemizygous mutation of c.521A>C was detected in the ABCD1 gene of the patient, and his mother has the same site heterozygous mutation. Therefore, this patient was diagnosed as "X-linked adrenoleukodystrophy". During the follow-up, adrenocortical hypothyroidism did not improve, and brain MRI showed few high-FLAIR signals in the white matter of the right radial corona and left parietal lobe, suggesting possible brain injury. X-ALD patients with only skin manifestations but no neurological abnormalities are easily neglected, but early diagnosis and early intervention are important ways to delay the progression of this disease. Therefore, genetic testing for early X-ALD is recommended in all male children patients with skin pigmentation as the sole clinical presentation and subsequent diagnosis of adrenal hypofunction.

Pigmentary anomaly caused by mosaic 3q22.2q29 duplication.

A 39-year-old woman sought advice regarding potential risks to her offspring due to previous possible diagnosis of incontinentia pigmenti. She had linear hyperpigmentation along the lines of Blaschko affecting the upper and lower limbs, and skin-coloured papules on the left palm. Ophthalmoscopy revealed hypopigmented spots in the macular region of the retina in each eye due to focal areas of depigmentation of the retinal pigment epithelium. An array comparative genomic hybridization on DNA extracted from a skin biopsy revealed a 63.63-Mb duplication, arr[GRCh37] 3q22.2q29(134212001_197837069)x3, on the long arm of chromosome 3. This case is an example of genetic mosaicism resulting from a de novo genetic defect arising at some point in embryonic development. Click here for the corresponding questions to this CME article.

Hyperpigmentation in a Chinese family with autosomal dominant Cole disease.

Cole disease (OMIM 615522), caused by mutations in ENPP1, is a rare autosomal dominant or recessive genodermatosis characterized by guttate hypopigmentation and punctate palmoplantar keratoderma. To date, a few cases with autosomal recessive inheritance had been reported with hyperpigmentation. The aim of this case report was to investigate the molecular basis of individuals with hyperpigmentation, hypopigmentation and punctate keratoderma in a Chinese family. A Chinese pedigree of suspected Cole disease with hyperpigmentation was subjected to mutation detection in the ENPP1 gene. All exons of the ENPP1 gene and adjacent exon-intron border sequences were amplified using polymerase chain reaction and directly sequenced. Three-dimensional (3D) models of the wild-type and mutated ENPP1 proteins were predicted by PyMOL viewer. Both of the proband and his affected father carried a heterozygous missense mutation p.C176R in ENPP1. In silico modelling of the ENPP1 wild-type and ENPP1 with the p.C176R mutation showed the residue Arg-176 disturbed the fold of the loop conformation. Based on clinical and genetic findings, a diagnosis of Cole disease was made. We identified a heterozygous mutation, p.C176R, in the ENPP1 gene in a Chinese family with Cole disease. This study clearly showed that hyperpigmentation could also occur in Cole disease in cases with autosomal dominant inheritance. Our data expand the phenotypic spectrum of ENPP1 mutations underlying Cole disease.

Upregulated Guanine Deaminase Is Involved in Hyperpigmentation of Seborrheic Keratosis via Uric Acid Release.

Seborrheic keratosis, which is a benign tumor composed of epidermal keratinocytes, develops common in the elderly. Uric acid generated by upregulated guanine deaminase (GDA) has been identified to cause UV-induced keratinocyte senescence in seborrheic keratosis. Seborrheic keratosis is also frequently pigmented. Growing evidences indicate that hyperuricemia is a risk factor of acanthosis nigricans, an acquired skin hyperpigmentation. The objective of this study was to investigate role of GDA and its metabolic end product, uric acid, in hyperpigmentation of patients with seborrheic keratosis using their lesional and non-lesional skin specimen sets and cultured primary human epidermal keratinocytes with or without GDA overexpression or uric acid treatment. GDA-overexpressing keratinocytes or their conditioned media containing uric acid increased expression levels of MITF and tyrosinase in melanocytes. Uric acid released from keratinocytes was facilitated by ABCG2 transporter with the help of PDZK1 interaction. Released uric acid was taken by URAT1 transporter in melanocytes, stimulating melanogenesis through p38 MAPK activation. Overall, GDA upregulation in seborrheic keratosis plays a role in melanogenesis via its metabolic end product uric acid, suggesting that seborrheic keratosis as an example of hyperpigmentation associated with photoaging.

De novo mutation in KITLG gene causes a variant of Familial Progressive Hyper- and Hypo-pigmentation (FPHH).

Familial Progressive Hyper- and Hypopigmentation is a pigmentary disorder characterized by a mix of hypo- and hyperpigmented lesions, café-au-lait spots and hypopigmented ash-leaf macules. The disorder was previously linked to KITLG and various mutations have been reported to segregate in different families. Furthermore, association between KITLG mutations and malignancies was also suggested. Exome and SANGER sequencing were performed for identification of KITLG mutations. Functional in silico analyses were additionally performed to assess the findings. We identified a de novo mutation in exon 4 of KITLG gene causing NM_000899.4:c.[329A>T] (chr12:88912508A>T) leading to NP_000890.1:p.(Asp110Val) substitution in the 3rd alpha helix. It was predicted as pathogenic, located in a conserved region and causing an increase in hydrophobicity in the KITLG protein. Our findings clearly confirm an additional hot spot of KITLG mutations in the 3rd alpha helix, which very likely increases the risk of malignancies. To our knowledge the present study provides the strongest evidence of association of the KITLG mutation with both Familial Progressive Hyper- and Hypopigmentation and malignancy due to its' location on somatic cancer mutation locus. Additionally we also address difficulties with classification of the unique phenotype and propose a subtype within broader diagnosis.

Amyloidosis cutis dyschromica cases caused by GPNMB mutations with different inheritance patterns.

BACKGROUND: Amyloidosis cutis dyschromica (ACD) is a rare form of primary cutaneous amyloidosis featured by reticulate dotted hypo- and hyperpigmentation. Recently, loss-of-function mutations in GPNMB, encoding glycoprotein (transmembrane) nonmetastatic melanoma protein B, were found in autosomal-recessive or semi-dominant ACD. OBJECTIVE: This study aims to detect the genetic defect underlying ACD in nine separate cases and to investigate the functional consequences of the mutants. METHODS: Nine ACD cases were collected including eight with autosomal-recessive pattern and one with autosomal-dominant pattern. Whole-exome sequencing or Sanger sequencing of the GPNMB gene was performed to detect the pathogenic mutations. Haplotype analysis was employed to determine the origin of mutation c.565C > T using adjacent highly polymorphic SNPs. Immunoblotting and subcellular localization assessments were performed to evaluate the expression of the mutants using HEK293 cells transfected with the GPNMB constructs. RESULTS: We detected four recurrent mutations (c.393 T > G, p.Y131*; c.565C > T, p.R189*; c.1056delT, p.P353Lfs*20; c.1238 G > C, p.C413S) and two novel mutations (c.935delA, p.N312Tfs*4; c.969 T > A, p.C323*) in GPNMB. Mutation c.565C > T found in six separate ACD cases shared a common haplotype. The two novel mutations caused a decreased abundance of truncated proteins. The c.1238 G > C mutation, which was detected in the autosomal-dominant case, caused abnormal reticular subcellular localization of the protein. A major percentage of wildtype changed its expression pattern when co-expressed with this mutant. CONCLUSIONS: Our findings proved that the recurrent mutation c.565C > T originated from a founder effect. The autosomal-dominant ACD associated mutation p.C413S played its pathogenic role through a dominant-negative effect on wild-type GPNMB. This study expands the genotype and inherited modes of ACD and improves our understanding of the pathogenesis of this disorder.

Bannayan-Riley-Ruvalcaba syndrome with gingival hyperpigmentation and facial papules.

One of the distinctive cutaneous manifestations of Bannayan-Riley-Ruvalcaba syndrome (BRRS), a PTEN hamartoma tumor syndrome, is penile pigmented macules. We present a 13-year-old boy with gingival hyperpigmentation along with facial and ear angiofibromas in the context of a BRRS-concordant phenotype and PTEN hamartoma tumor syndrome genotype. To our knowledge, these two findings have not been previously reported with BRRS and may expand the known phenotype of this disorder.

Dowling-Degos disease: a review.

Dowling-Degos disease is a rare autosomal dominant genodermatosis. It is characterized by acquired reticulate hyperpigmentation over the flexures, comedone-like follicular papules, and pitted perioral scars that usually develop during adulthood. Mutations in genes affecting melanosome transfer, and melanocyte and keratinocyte differentiation have been implicated in the pathogenesis of this disease. These genes include KRT5, POFUT1, POGLUT1 and, most recently, PSENEN. Dowling-Degos disease can be found in isolation or with other associated findings, most notably hidradenitis suppurativa. This condition belongs to a spectrum of conditions that all result in reticulate hyperpigmentation that at times are hard to distinguish from each other. The most closely linked entity is Galli-Galli, which is clinically indistinguishable from Dowling-Degos disease and can only be distinguished by the presence of acantholysis on microscopy. Unfortunately, Dowling-Degos disease is generally progressive and recalcitrant to treatment.

Strain difference in transgene-induced tumorigenesis and suppressive effect of ionizing radiation.

Transgenic expression in medaka of the Xiphophorus oncogene xmrk, under a pigment cell specific mitf promoter, induces hyperpigmentation and pigment cell tumors. In this study, we crossed the Hd-rR and HNI inbred strains because complete genome information is readily available for molecular and genetic analysis. We prepared an Hd-rR (p53+/-, p53-/-) and Hd-rR HNI hybrid (p53+/-) fish-based xmrk model system to study the progression of pigment cells from hyperpigmentation to malignant tumors on different genetic backgrounds. In all strains examined, most of the initial hyperpigmentation occurred in the posterior region. On the Hd-rR background, mitf:xmrk-induced tumorigenesis was less frequent in p53+/- fish than in p53-/- fish. The incidence of hyperpigmentation was more frequent in Hd-rR/HNI hybrids than in Hd-rR homozygotes; however, the frequency of malignant tumors was low, which suggested the presence of a tumor suppressor in HNI genetic background fish. The effects on tumorigenesis in xmrk-transgenic immature medaka of a single 1.3 Gy irradiation was assessed by quantifying tumor progression over 4 consecutive months. The results demonstrate that irradiation has a different level of suppressive effect on the frequency of hyperpigmentation in purebred Hd-rR compared with hybrids.

Newborn transient patterned hyperpigmentation and anophthalmia / Patrón de hiperpigmentación transitoria del recién nacido y anoftalmia

Abstract Background: Transient pigmentary lines of the newborn are uncommon cutaneous lesions of unknown etiology. To date, only a few cases have been described. Case report: A patient with a combination of transient pigmentary lines and ocular malformation is described. Molecular analysis of the SRY-box 2 (SOX2) and MIFT genes was conducted to rule out any monogenetic etiology. Conclusions: Worldwide, this is the eighth case of transient pigmentary lines of the newborn reported, and the first associated with anophthalmia. No mutations in the analyzed genes (SOX2 and MIFT) were identified. Therefore, somatic mutations could be responsible for this anomaly.

Resumen Introducción: Las líneas transitorias pigmentarias del recién nacido son lesiones cutáneas poco comunes. A la fecha, pocos casos se han descrito. Caso clínico: Paciente neonato con la combinación de líneas transitorias hiperpigmentadas y una malformación ocular. Se realizó secuenciación molecular de los genes SOX2 y MIFT para descartar una etiología monogénica. Conclusiones: En todo el mundo, este es el octavo caso reportado de líneas transitorias hiperpigmentadas del recién nacido, y el primero asociado con anoftalmia. No se identificaron mutaciones en los genes estudiados (SOX2 y MIFT). Por lo tanto, las mutaciones somáticas pueden ser la causa de la afección.

Novel mutation in the KITLG gene in familial progressive hyperpigmentation with or without hypopigmentation.

We herein report a novel mutation in familial progressive hyper- and hypopigmentation (FPHH). The KITLG gene encoding the KIT ligand protein is a disease-causing gene for FPHH. Various disease-causing gain-of-function mutations, which reside within or adjacent to the conserved VTNN motif of this gene, have been described to date. We have now identified a novel KITLG mutation, c.337G>A (p.Glu113Lys), in FPHH which is located within another ligand-receptor interaction site.

Long-term outcome of partial P450 side-chain cleavage enzyme deficiency in three brothers: the importance of early diagnosis.

OBJECTIVE: CYP11A1 mutations cause P450 side-chain cleavage (scc) deficiency, a rare form of congenital adrenal hyperplasia with a wide clinical spectrum. We detail the phenotype and evolution in a male sibship identified by HaloPlex targeted capture array. FAMILY STUDY: The youngest of three brothers from a non-consanguineous Scottish family presented with hyperpigmentation at 3.7 years. Investigation showed grossly impaired glucocorticoid function with ACTH elevation, moderately impaired mineralocorticoid function, and normal external genitalia. The older brothers were found to be pigmented also, with glucocorticoid impairment but normal electrolytes. Linkage studies in 2002 showed that all three brothers had inherited the same critical regions of the maternal X chromosome suggesting an X-linked disorder, but analysis of NR0B1 (DAX-1, adrenal hypoplasia) and ABCD1 (adrenoleukodystrophy) were negative. In 2016, next-generation sequencing revealed compound heterozygosity for the rs6161 variant in CYP11A1 (c.940G>A, p.Glu314Lys), together with a severely disruptive frameshift mutation (c.790_802del, K264Lfs*5). The brothers were stable on hydrocortisone and fludrocortisone replacement, testicular volumes (15-20 mL), and serum testosterone levels (24.7, 33.3, and 27.2 nmol/L) were normal, but FSH (41.2 µ/L) was elevated in the proband. The latter had undergone left orchidectomy for suspected malignancy at the age of 25 years and was attending a fertility clinic for oligospermia. Initial histology was reported as showing nodular Leydig cell hyperplasia. However, histological review using CD56 staining confirmed testicular adrenal rest cell tumour (TART). CONCLUSION: This kinship with partial P450scc deficiency demonstrates the importance of precise diagnosis in primary adrenal insufficiency to ensure appropriate counselling and management, particularly of TART.

Genetic and clinical characterization of 73 Pigmentary Mosaicism patients: revealing the genetic basis of clinical manifestations.

BACKGROUND: Pigmentary mosaicism constitutes a heterogeneous group of skin pigmentation alterations associated with multisystem involvement. The aim of this study was to establish a complete cytogenetic and molecular characterization of PM patients, emphasizing on searching for possible low chromosomal mosaicism and on establishing an accurate genotype-phenotype correlation. RESULTS: A total of 73 patients were included (3 months to 18 years of age), 52% male and 48% female. Observed in 69 (95%) patients, the most frequent pattern of pigmentation was fine and whorled BL, which was associated with disseminated skin extent in 41 (59%) patients. Central nervous system (84%) alterations were the most frequent observed in the group of patients, followed by the musculoskeletal (53%) and ophthalmologic (27%) alterations. Considering the pattern of pigmentation, no significant differences in association with skin extent or extracutaneous manifestations were detected. Following a strict cytogenetic analysis strategy, screening metaphases from three different tissues (peripheral blood, hyperpigmented and hypopigmented skin) we found that 23/73 patients had chromosomal abnormalities classified as follows: 1) Mosaic with 2 or more different cell lines with structural alterations n = 19; 2) Polyploidy (mosaic) n = 1 and 3) Alterations in all cells in three different tissues n = 3. SNP array, array CGH and FISH were useful for the complete characterization of the chromosomal aberrations, for the detection of microdeletions in patients with normal karyotype but with strong clinical suspicious of chromosomal alteration, and for a better establishment of genotype-phenotype correlation. In 2 patients we found genes associated with some of the extracutaneous manifestations (SHH, MNX1, PPP2R2C). CONCLUSIONS: This group of 73 patients finely described is the largest series of patients with pigmentary mosaicism reported worldwide. As we showed in this study, the followed analysis strategy allowed the detection of cytogenetic and molecular abnormalities, and made possible the establishment of genotype-phenotype associations in some patients. An important limitation of our study was the analysis of fibroblasts cultures instead of melanocytes and keratinocytes. In some cases the direct molecular DNA analysis of skin biopsy could be another choice.