Hereditary congenital hypopigmented and hyperpigmented macules (Westerhof syndrome) in two siblings

Identification of a novel mutation in the KITLG gene in a Chinese family with familial progressive hyper- and hypopigmentation

Background

Familial progressive hyper- and hypopigmentation (FPHH, MIM 145250) is a rare hereditary skin disorder that is predominantly characterized by progressive, diffuse, partly blotchy hyperpigmented lesions intermingled with scattered hypopigmented spots, lentigines and sometimes Cafe-au-lait spots (CALs). Heterozygous mutations of the KIT ligand (KITLG, MIM 184745) gene are responsible for FPHH. To date, only eight KITLG mutations have been reported to be associated with FPHH, and no clear genotype–phenotype correlations have been established. This study aimed to identify the causative mutations in the KITLG gene in two Chinese FPHH patients.

Methods

Direct sequencing of the coding regions of KITLG was performed. Pathogenicity prediction was performed using bioinformatics tools, including SIFT, Polyphen2, and SWISS-MODEL, and the results were further evaluated according to the 2015 American College of Medical Genetics and Genomics (ACMG) guidelines.

Results

The novel mutation c.104A > T (p.Asn35Ile) and the recurrent mutation c.101C > T (p.Thr34Ile) in KITLG were identified. As shown using SIFT and Polyphen-2 software, both mutations identified in this study were predicted to be detrimental variations. Three-dimensional protein structure modeling indicated that the mutant KITLG proteins might affect the affinity of KITLG for its receptor, c-KIT. According to the 2015 ACMG guidelines, the novel mutation c.104A > T was ‘likely pathogenic’.

Conclusions

To date, most of the identified KITLG mutations have been clustered within the conserved VTNNV motif (amino acids 33–37) in exon 2. The known mutations are only involved in 33 V, 34 T, 36 N, and 37 V but not 35 N. We have now identified a novel mutation in KITLG, c.104A > T, that was first reported in FPHH within the conserved 35 N motif. These results strengthen our understanding of FPHH and expand the mutational spectrum of the KITLG gene.

Familial progressive hyper- and hypopigmentation: a report on a Chinese family and evidence for genetic heterogeneity

BACKGROUND

Familial progressive hyper- and hypopigmentation (FPHH) is a rare genodermatosis that is characterized by diffuse hyper- and hypopigmented spots on the skin and mucous membranes. It is caused by a pathogenic mutation of the KITLG gene.

OBJECTIVES

To investigate the clinical features and mutation of the KITLG gene in a Chinese family with FPHH.

METHODS

Histopathological and immunohistochemical analysis of lesions from the proband was performed. The KITLG gene was screened for the presence of mutations.

RESULTS

A Chinese family containing 14 individuals with FPHH was described, and the proband was a 5-year-old girl showing diffuse hyper- and hypopigmented lesions on her extremities and trunk. Histopathological and immunohistochemical staining for S100 and HMB45 of skin biopsy specimens from the hyperpigmented areas showed a striking increase in melanin throughout the epidermis, especially in the basal cell layer, and staining of hypopigmented area specimens displayed lower levels of melanin in the epidermis. Mutation analysis of the KITLG gene was performed, but no mutation was found.

STUDY LIMITATIONS

The new pathogenic gene was not found.

CONCLUSION

A family with FPHH was described. Analysis revealed that its members did not have any mutations of the KITLG gene, which provided evidence for genetic heterogeneity of this genodermatosis.

Infancy- and childhood-onset dyschromatoses

The dyschromatoses are a group of pigmentary disorders characterized clinically by mixed and often guttate hypopigmented and hyperpigmented lesions. There are many conditions that present with dyschromatosis, including genodermatoses, inflammatory skin diseases, infections, drug and chemical use, and nutritional disorders. Some conditions have extracutaneous features. Poikiloderma (a combination of hypo- and hyperpigmentation with telangiectasia and atrophy) must be excluded. In this article, we describe the dyschromatoses typically presenting in infancy and childhood, most of which are genodermatoses. The approach we have taken in classifying them is based on organ involvement. We hope this article will serve as a guide for dermatologists to the recognition of these uncommon conditions.

Spectrum of skeletal abnormalities in a complex malformation syndrome with "cutis tricolor" (Ruggieri-Happle syndrome)

BACKGROUND

The term cutis tricolor describes the combination of congenital hyper- and hypopigmented skin lesions in close proximity to each other in a background of normal complexion. This phenomenon has been reported: (i) as a purely cutaneous trait; (ii) as a part of a complex malformation syndrome (Ruggieri-Happle syndrome - RHS); (iii) as a distinct type [cutis tricolor parvimaculata]; (iv) in association with other (e.g. vascular) skin disturbances.

OBJECTIVES

To delineate the spectrum of skeletal defects in cutis tricolor.

METHODS

Retrospective and prospective analysis of skeletal surveys in 14 subjects (eight men; six women; aged 2-28 years) with cutis tricolor [4 purely cutaneous trait; 10 syndromic (RHS)].

RESULTS

Bone abnormalities were recorded in 71.4% (10/14) of patients [100% (10/10) of cases with (other-than-skeletal) extra-cutaneous manifestations vs. null (0/4) in cases with purely cutaneous traits] and included overall small skull (n = 6); prognathism (n = 6); 'J'-shaped pituitary fossa (n = 1); absence of atlas posterior arch (n = 3); frontal bossing (n = 6); scoliosis (n = 9) with kyphosis (n = 6) and/or lordosis (n = 6); vertebral (n = 9) and ribs (n = 4) defects. Negative ZFHX1B gene analyses excluded overlaps with Mowat-Wilson syndrome.

CONCLUSIONS

Cutis tricolor may be a marker of underlying skeletal involvement particularly in subjects with a complex syndromic (RHS) phenotype.