Onychodystrophy in congenital linear porokeratosis

Two Novel and Three Recurrent Mutations in the Mevalonate Pathway Genes in Chinese Patients with Porokeratosis

Purpose

Porokeratosis (PK) is a chronic autosomal-dominant cutaneous keratinization disorder exhibiting clinical and genetic heterogeneity. Mevalonate decarboxylase (MVD), farnesyl diphosphate synthase (FDPS), phosphomevalonate kinase(PMVK), and mevalonate kinase genes(MVK), which encode the mevalonate pathway, are disease-causing genes in PK.

Patients and Methods

Data and blood samples were collected from two Chinese families and five sporadic patients with porokeratosis. Whole-exome and Sanger sequencing were performed to detect pathogenic gene mutation in the patients.

Results

Five heterozygous mutations were identified, including a novel FDPS stop-gain mutation c.438T>G (p.Tyr146Ter), a novel MVD missense mutation c.683G>C (p.R228P), and three previously reported MVD mutations: c.746T>C (p.F249S), c.875A>G (p.N292S), and c.1111_1113del (p.371_371del). The novel FDPS c.438T>G mutation was predicted as "disease-causing" (p = 1) by Mutation Taster. The other novel MVD c.683G>C was also predicted as "deleterious" (score = 0.00) by Sorting Intolerant From Tolerant (SIFT), "probably damaging" (score = 1) by PolyPhen2, and "disease-causing" (p = 0.999) by Mutation Taster.

Conclusion

Our results extended the mutation spectrum of mevalonate pathway genes in porokeratosis and provided useful strategies for a more accurate diagnosis and genetic counseling.

Porokeratoses-A Comprehensive Review on the Genetics and Metabolomics, Imaging Methods and Management of Common Clinical Variants

Porokeratosis is a heterogeneous group of keratinising disorders characterised by the presence of particular microscopic structural changes, namely the presence of the cornoid lamella. This structure develops as a consequence of a defective isoprenoid pathway, critical for cholesterol synthesis. Commonly recognised variants include disseminated superficial actinic porokeratosis, disseminated superficial porokeratosis, porokeratosis of Mibelli, palmoplantar porokeratosis (including porokeratosis palmaris et plantaris disseminata and punctate porokeratosis), linear porokeratosis, verrucous porokeratosis (also known as genitogluteal porokeratosis), follicular porokeratosis and porokeratoma. Apart from the clinical presentation and epidemiology of each variant listed, this review aims at providing up-to-date information on the precise genetic background, introduces imaging methods facilitating the diagnosis (conventional and ultraviolet-induced fluorescence dermatoscopy, reflectance confocal microscopy and pathology), discusses their oncogenic potential and reviews the literature data on the efficacy of the treatment used, including the drugs directly targeting the isoprenoid-mevalonate pathway.

Porokeratosis of the Nail Unit: Case Series and Review

Background

The lesions of porokeratosis (PK) lead to skin atrophy and scarring as long as they spread centrifugally. PK affecting the nail unit is seldom described.

Objective

The aim was to revise the previously reported cases of ungual PK and to present 3 new cases.

Methods

A PubMed search was performed with the keywords "nail" and "porokeratosis." Previously reported cases as well as 3 new cases are depicted in tables.

Results

Only 11 cases of ungual PK were found; 3 new cases have been added. All patients presented with typical lesions of PK (Mibelli, isolated, segmental, or ostial eccrine types) that happened to affect nails due to nail matrix or nail bed compromise, resulting in mild to severe nail scarring, including irreversible anonychia. The present 3 case series contrast with the previous single case reports.

Conclusions

PK affecting the nails is exceedingly rare. Changes in nails affected by PK are irreversible, since, as on the skin, this is a chronic scarring process.

Onychodystrophy due to porokeratosis of Mibelli: a rare association

Porokeratosis is a specific keratinization disorder that manifests clinically as well-demarcated annular or linear keratotic plaques of various sizes and forms and with distinguished histology showing cornoid lamella, which is a column of closely packed parakeratotic cells extending through the stratum corneum. Nail changes secondary to porokeratotic lesions involving digits are quite uncommon and rarely reported in the porokeratosis of Mibelli (PM) subtype. Here we report the case of a young girl with a PM lesion over the hand along with nail dystrophy of the involved digit.

A Case of Extensive Linear Porokeratosis with Evaluation of Topical Tretinoinversus5-Flourouracil as Treatment Modalities

A 19-year-old male presented with linear raised lesions over extensive areas of his body that followed Blaschko's lines. The lesions were asymptomatic with ridged borders. Histopathology confirmed a diagnosis of porokeratosis. He was given topical tretinoin and topical flourouracil for local application on specified areas. The cosmetic acceptability and the safety profile of tretinoin were found to be better than those of flourouracil. However, both the agents were equally efficacious. A rare case of extensive porokeratosis with comparative evaluation of two treatment modalities is hereby presented.

Generalized linear porokeratosis

A 23-year-old woman was seen for widespread skin lesions present since the age of 2.5 years. Twenty years ago, she developed a brown macular lesion on her right buttock. The lesion became hyperkeratotic and subsequently spread through the posterior aspect of her right leg. It later spread to the right side of the trunk and to the right arm. When she was 9 years old, she developed similar lesions on her left arm and leg. After she was 13 years old, no new skin lesions appeared. There was no family history of similar lesions. On examination, there were numerous linear and whorled, reddish-brown, hyperkeratotic plaques, with central atrophy and raised borders, following Blaschko's lines on all of the extremities. These lesions on the extremities extended to the dorsum of the hands and feet (Fig. 1). She had hyperkeratotic lesions on the pressure points of both of the soles, but no palm involvement. The number of lesions on the right side was greater than that on the left. Reddish-brown annular plaques with central atrophy and raised borders, appearing in zosteriform configuration, and numerous individual 2-3-mm erythematous lichenoid papules were observed on the right side of the thorax and the right inguinal region (Fig. 2). No face, scalp, or mucous membrane involvement was seen. The nails of the second and fifth fingers of the right hand and the nail of the third finger of the left hand showed nail dystrophy with longitudinal ridges and pterygium. All the nails of the right foot and the nails of the first and fifth toes of the left foot showed dystrophic changes with subungual keratosis. The patient was otherwise in good health. Two biopsy specimens taken from a hyperkeratotic plaque and a lichenoid papule showed an epidermal invagination with angulated parakeratotic tier, denoting cornoid lamella. The epidermis just underneath the cornoid lamella displayed vacuolization and the granular layer was absent. The adjacent epidermis was atrophic, and hydropic degeneration within the basal cell layer was seen. In the dermis, a nonspecific, mild, chronic, inflammatory cell infiltrate, telangiectatic vessels, and pigment-laden macrophages were present. These findings were consistent with linear porokeratosis (Fig. 3). Microscopic examinations and mycologic cultures of the nails were negative. We decided to treat our case systemically with retinoids, but the patient refused this therapy. So, topical tretinoin 0.05% was started once a day. A marked improvement was observed in hyperkeratosis through the first 4 weeks of treatment and plateaued at 8 weeks. After 10 weeks, the lesions had almost disappeared. We planned to continue the applications every other day. One year later, she remains stable with application of topical tretinoin 0.05% twice a week and is satisfied with the final appearance. She is under regular follow-up.