Hereditary 'white nails': a genetic and structural study

Leukonychia: What Can White Nails Tell Us?

Changes in nail color can provide important clues of underlying systemic and skin disease. In particular, white discoloration (leukonychia) has a high prevalence with a wide array of potential relevant causes, from simple manicure habits to life-threatening liver or kidney failure. Therefore, a reliable assessment of the patient with leukonychia is essential. In the past, two classifications for leukonychia have been presented. The morphological classifies the nail according to the distribution of the white lines: total, partial, transversal, and longitudinal leukonychia. Mees’ and Muehrcke’s lines are examples of transversal leukonychia, while Terry’s and Lindsay’s nails are examples of total and partial leukonychia. The anatomical classifies according to the structure responsible for the white color: the nail plate in true leukonychia, the nail bed in apparent leukonychia, and the surface only in pseudoleukonychia. In this review, both morphological and anatomical features have been combined in an algorithm that enables clinicians to approach leukonychia efficiently and effectively.

Acquired Leukonychia of the Distal Nail Plate: A Morphologic and Proteomic Analysis

Leukonychia, or whitening of the nail plate, is a common disease that was first described in 1919. Leukonychia is classified as acquired or congenital and may be due to abnormality of the nail bed (pseudoleukonychia) or nail plate (true leukonychia). The distal whitened area of the nail plate was clipped from a 31-year-old woman with striated leukonychia and a 32-year-old man and 34-year-old woman with punctate leukonychia. Routine hematoxylin and eosin staining of all clipped samples was performed. A piece of nail with leukonychia and a normal nail from case 2 were sent to the Mayo Clinic for mass spectrometric analysis. On hematoxylin and eosin examination, all leukonychia samples showed odd-appearing eosinophilic linear parakeratinization in the mid-segment of the nail plate. Mass spectrometric analysis of case 2 revealed serum proteins (albumin, serotransferrin IgG, gamma chain, IgG lambda chain, and haptoglobulin) and hair proteins that were not found in the keratin content of the normal nail (keratin type Ha1 and cuticular keratin Ha4). This is the first description of odd-appearing linear parakeratosis and the first proteomic analysis showing abnormal protein content in acquired leukonychia.

Whole exome sequencing identifies a novel dominant missense mutation underlying leukonychia in a Pakistani family

Hereditary leukonychia (also known as porcelain nails or white nails) is a genetic disorder. It may exist as an isolated feature or associated with other cutaneous or systemic disorders. Although a number of genes have been described to cause leukonychia, still the underlying genetic etiologies of many cases remain unknown. Here, we report a Pakistani family presenting leukonychia and koilonychia nails in mother and five of her kids. All the affected individuals had white to pale nails in appearance exhibiting complete and partial leukonychia, respectively. Similarly, nails of finger and toe appeared brittle and concave, showing the characteristics features of koilonychia. Whole exome sequencing and subsequent Sanger sequencing identified a pathogenic novel missense mutation (c.1390G>A, p.Glu464Lys) in PLCD1, co-segregating with the disorder in an autosomal dominant pattern. In silico prediction tools supported the pathogenicity of the identified mutation. Literature review determined that mutations in PLCD1 only cause leukonychia. Therefore, our findings add another pathogenic variant to the PLCD1 mutation pool causing leukonychia that would help to understand the underlying molecular mechanism.

Identification of a novel PLCD1 mutation in Chinese Han pedigree with hereditary leukonychia and koilonychia

BACKGROUND

Hereditary leukonychia is a rare nail dystrophy characterized by distinctive whitening of the nail plate. Mutations in the PLCD1 gene have been identified as a major causative factor in hereditary leukonychia (HL). However, few reports have analyzed the relationship between genotype and phenotype, especially in Chinese HL patients. Our study aims to explore the typical clinical features of hereditary leukonychia cases in Chinese Han pedigree and the correlations with PLCD1 gene mutation.

PATIENTS AND METHODS

In this study, two Chinese patients presented with leukonychia and koilonychia. Whole-exome sequencing (WES) was performed to screen for the mutations in PLCD1 gene and other candidate genes for hereditary leukonychia. Parents with PLCD1 mutation were selected for Sanger sequencing.

RESULTS

A novel heterozygote missense mutation in exon 9 of PLCD1 gene was identified in the proband and his mother. Whole-exome sequencing revealed both, the proband (III.5) and his mother (II.4) carrying c.1451A>G mutation, while other family members had a normal sequence of the PLCD1 gene.

CONCLUSION

For the first time, a hereditary leukonychia case with PLCD1 mutation has been described in Chinese Han pedigree. This finding suggests the PLCD1 mutation maybe involved in hereditary leukonychia.

Hereditary Leukonychia Totalis: A Case Report and Review of the Literature

Leukonychia is defined as white discoloration of the nails caused by an abnormal keratinization of the nail matrix. Congenital leukonychia totalis is a rare nail disorder, which is typically inherited in an autosomal dominant pattern. This condition can be presented as an isolated condition or in association with systemic diseases. We report a case of a 7-year-old Thai boy who developed asymptomatic white discoloration of all the nails since birth, with an absence of any predisposing factors or associated conditions.

Mutations in PLCδ1 associated with hereditary leukonychia display divergent PIP2 hydrolytic function

Hereditary leukonychia is a rare genetic nail disorder characterized by distinctive whitening of the nail plate of all 20 nails. Hereditary leukonychia may exist as an isolated feature, or in simultaneous occurrence with other cutaneous or systemic pathologies. Associations between hereditary leukonychia and mutations in the gene encoding phospholipase C delta-1 (PLCδ1) have previously been identified. However, the molecular mechanisms underlying PLCδ1 mutations and hereditary leukonychia remain uncharacterized. In the present study, we introduced hereditary leukonychia-linked human PLCδ1 mutations (C209R, A574T and S740R) into equivalent residues of rat PLCδ1 (C188R, A553T and S719R), and investigated their effect on the biophysical and biochemical properties of the PLCδ1 protein. Our data suggest that these PLCδ1 mutations associated with hereditary leukonychia do not uniformly alter the enzymatic ability of this protein leading to loss/gain of function, but result in significantly divergent enzymatic properties. We demonstrate here for the first time the importance of PLC-mediated calcium (Ca²⁺ ) signalling within the manifestation of hereditary leukonychia. PLCδ1 is almost ubiquitous in mammalian cells, which may explain why hereditary leukonychia manifests in association with other systemic pathologies relating to keratin expression.

Hereditary leukonychia, or porcelain nails, resulting from mutations in PLCD1

Hereditary leukonychia (porcelain nails or white nails) is a rare nail disorder with an unknown genetic basis. To identify variants in a gene underlying this phenotype, we identified four families of Pakistani origin showing features of hereditary leukonychia. All 20 nails of each affected individual were chalky and white in appearance, consistent with total leukonychia, with no other cutaneous, appendageal, or systemic findings. By using Affymetrix 10K chip, we established linkage to chromosome 3p21.3-p22 with a LOD score (Z) of 5.1. We identified pathogenic mutations in PLCD1 in all four families, which encodes phosphoinositide-specific phospholipase C delta 1 subunit, a key enzyme in phosphoinositide metabolism. We then identified localization of PLCD1 in the nail matrix. It was recently shown that PLCD1 is a component of the human nail plate by proteomic analysis and is localized in the matrix of human nails. Furthermore, mutations detected in PLCD1 resulted in reduced enzymatic activity in vitro. Our data show that mutations in PLCD1 underlie hereditary leukonychia, revealing a gene involved in molecular control of nail growth.

Congenital isolated leukonychia totalis in three Egyptian sibs

Isolated leukonychia totalis is a rare condition of nails with mainly an autosomal dominant pattern of inheritance. In this report, we present three sibs (a sister and two brothers) with isolated congenital leukonychia totalis, without any manifestation among parents and other family members. The sibs had similar facial features and were offspring of consanguineous Egyptian parents. We discussed possible mechanisms of inheritance and suggested an autosomal recessive mode of transmission.

Proteomic analysis of human nail plate

Shotgun proteomic analysis of the human nail plate identified 144 proteins in samples from Causcasian volunteers. The 30 identified proteins solubilized by detergent and reducing agent, 90% of the total nail plate mass, were primarily keratins and keratin associated proteins. Keratins comprised a majority of the detergent-insoluble fraction as well, but numerous cytoplasmic, membrane, and junctional proteins and histones were also identified, indicating broad use by transglutaminases of available proteins as substrates for cross-linking. Two novel membrane proteins were identified, also found in the hair shaft, for which mRNAs were detected only at very low levels by real-time polymerase chain reaction in other tissues. Parallel analyses of nail samples from volunteers from Inner Mongolia, China gave essentially the same protein profiles. Comparison of the profiles of nail plate and hair shaft from the latter volunteers revealed extensive overlap of protein constituents. Analyses of samples from an arsenic-exposed population revealed few proteins whose levels were altered substantially but raised the possibility of detecting sensitive individuals in this way.

A family with leukonychia totalis

A family presented to our dermatology clinic with a complaint of white nails. Physical examination revealed clinical feature of leukonychia totalis and the presence of sensorineural hearing loss, palmo plantar keratoderma and knuckle pads (four essential criteria for the diagnosis of Bart Pumphrey syndrome).Three consecutive generations of this family were affected with variable presentations of Bart Pumphrey syndrome in male and female; and autosomal dominant pattern of inheritance.

Unexpected clinical involvement of hereditary total leuconychia with congenital fibrosis of the extraocular muscles in three generations

We report familial segregation of hereditary total leuconychia (HTL) with ptosis and restriction of ocular motility due to congenital fibrosis of the extraocular muscles type 1 (CFEOM1) in three generations. In this family, 4 people have HTL and ptosis, and there is restriction of ocular motility due to CFEOM1 in 10 members of the family. To our knowledge, this is the first description of familial segregation of CFEOM1 and HTL, and the second report of unexpected clinical involvement of CFEOM1. We suggest that CFEOM1 is not an isolated phenomenon in these cases. These phenotypes provide valuable insight into the function of the gene(s) localized to 12q13, giving a new perspective on the clinical component of molecular dysmorphology, but this requires further clarification.

Hereditary leukonychia totalis, acanthosis-nigricans-like lesions and hair dysplasia: a new syndrome?

Leukonychia is an ungueal discoloration or dyschromia. The hereditary form is rare. In the observations reported in the literature, leukonychia was total or sub-total, and was sometimes associated to other various symptoms. We report an original observation of hereditary leukonychia totalis in a father and two of his children, associated with acanthosis-nigricans-like lesions and hair dysplasia. These symptoms were also present in eight other members of the same family.