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

Pigmentary Changes in a Woman With Oral Lichen Planus

A woman in her 60s presented with oral lichen planus on hands and cheeks since childhood and also present in her parent and sibling. What is your diagnosis?

Cutaneous findings in Fanconi anemia

BACKGROUND

Fanconi anemia (FA) is a genetic disorder that results in bone marrow failure, physical abnormalities, and solid organ malignancies. The diagnosis of FA is often delayed because the early disease characteristics have not been well established.

OBJECTIVE

To outline the spectrum of cutaneous findings seen in patients with FA.

METHODS

A cross-sectional study in which patients with FA received a full-body skin examination. Patient characteristics are summarized with mean (SD) for continuous and count (%) for categorical variables. Poisson regression and logistic regression models were used to examine the relationships between pigmentary changes and patient characteristics.

RESULTS

At least 1 cutaneous pigmentary alteration was present in 96.8% of patients, most arising before the teenage years. The most common finding was café-au-lait macules. Other findings included hypopigmented macules, skin-fold freckle-like macules, extensive sun-exposed freckling, and both hypopigmented and hyperpigmented pigment macules.

LIMITATIONS

Patients received a single assessment, so the number of pigmentary changes could not be assessed over time.

CONCLUSIONS

Characteristic morphology of FA includes faint and ill-defined café-au-lait macules, hypopigmented skin-fold freckle-like macules and the concurrence of hypopigmented and hyperpigmented macules. The recognition of these findings could aid clinicians in making earlier diagnoses.

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.