Recessive mosaicism in ABCA12 causes blaschkoid congenital ichthyosiform erythroderma.

We report the unique case of a 3-year-old girl who presented with linear erythematosquamous lesions following the lines of Blaschko, suggestive of genetic mosaicism in the skin. Single-candidate gene analyses were performed on DNA from blood, excluding Conradi-Hünermann-Happle syndrome, erythrokeratodermia variabilis and a mosaic presentation of pityriasis rubra pilaris. With whole-exome sequencing (WES) on DNA from the patient's blood, a heterozygous missense mutation in exon 25 of the ABCA12 gene was detected. By manually scrutinizing the WES data, another low-percentage pathogenic frameshift mutation was found in the adjacent exon 26 of the same gene. This frameshift mutation was confirmed with Sanger sequencing in DNA isolated from a lesional skin biopsy. A subsequent cloning experiment was performed to prove that the patient is compound heterozygous for both mutations in the affected skin, explaining the blaschkoid ichthyosiform erythrodermic phenotype. The patient's phenotype was elucidated by the combination of a germline mutation and an acquired postzygotic mutation in ABCA12, resulting in the diagnosis of a mosaic manifestation of autosomal recessive congenital ichthyosis. Postzygotic compound allelic loss in autosomal recessive disorders is extremely rare and will not appear as the typical phenotype of the known germline mutation-associated disease. This is the first report of a proven biallelic mosaic presentation of an autosomal recessive genodermatosis, and we propose the term 'recessive mosaicism' for this kind of manifestation. What's already know about this topic? Specific mutations in the ABCA12 lipid transporter are known to cause different phenotypes like harlequin ichthyosis, congenital ichthyosiform erythroderma and lamellar ichthyosis. In mosaicism, two or more cell populations that are genetically different arise postzygotically in the developing embryo. In the skin, mosaicism can present itself in different patterns of affected skin, often caused by a dominant genetic mutation. What does this study add? We report a unique patient with blaschkoid congenital ichthyosiform erythroderma due to biallelic mutations, one inherited germline missense mutation and the other a postzygotic frameshift mutation in the ABCA12 gene. This study describes the diagnostic approach and applied research that can be used if one encounters a similar diagnostic dilemma with manifestations suspected for genetic mosaicism. We propose the term 'recessive mosaicism' for this kind of mosaic presentation of an autosomal recessive genodermatosis.

Genetic profiling of basal cell carcinomas detects postzygotic mosaicism in basal cell naevus syndrome.

Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene. Postzygotic mosaicism can also cause BCNS. Here we describe two patients, one with multiple basal cell carcinomas (BCCs) and one with clinical BCNS, who had no PTCH1 mutation in DNA extracted from blood. In both patients, we performed genetic analysis on different BCCs, revealing the presence of a shared PTCH1 mutation in all tumours. Our findings show that in patients with symptoms of BCNS and initial absence of a PTCH1 mutation in blood, genetic profiling of BCCs can detect postzygotic mosaicism. What's already known about this topic? Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene, but it can also be caused by low-grade postzygotic mosaicism in PTCH1. What does this study add? In patients suspected of having BCNS or patients with multiple basal cell carcinomas (BCCs) with a special distribution on the body and no mutation detected in blood, it is worthwhile to search for a shared PTCH1 mutation in their BCCs as this can detect postzygotic mosaicism. This information is important to ensure proper surveillance programmes, choose the right therapy and provide adequate genetic counselling.

Postzygotic mosaicism in basal cell naevus syndrome.

Basal cell naevus syndrome (BCNS) is an autosomal dominant disorder most commonly caused by a germline mutation in the Drosophila homologue of patched-1 gene (PTCH1). Here we describe a patient with clinical signs of BCNS, caused by postzygotic mosaicism of a PTCH1 mutation. We performed restriction fragment length polymorphism analysis and Droplet Digital polymerase chain reaction to determine the degree of mosaicism in different tissues of this patient. Our case shows that a relatively low-grade mosaicism can lead to clinical signs reminiscent of those caused by a germline mutation. This finding has important implications for genetic counselling and therefore is pivotal to recognize for dermatologists, as well as for clinical geneticists and clinical laboratory geneticists.

Photodynamic therapy vs. topical imiquimod for treatment of superficial basal cell carcinoma: a subgroup analysis within a noninferiority randomized controlled trial.

BACKGROUND: A recent noninferiority randomized controlled trial (RCT) indicated that imiquimod can be considered as superior to methylaminolevulinate photodynamic therapy (MAL-PDT) in the treatment of superficial basal cell carcinoma (sBCC). Knowledge of treatment effectiveness in subgroups of patients is of great value in clinical practice to select the most effective treatment for an individual patient with sBCC. OBJECTIVES: To explore whether the relative treatment effect of MAL-PDT and imiquimod is consistent across subgroups defined by patient and tumour characteristics. METHODS: Data were derived from a single-blinded, noninferiority, multicentre RCT comparing MAL-PDT, topical imiquimod and fluorouracil (ISRCTN79701845). Treatment success was defined as free of tumour recurrence at 12-month follow-up. Subgroup analyses were performed for subgroups defined by sex, age, tumour location and tumour size. RESULTS: Two hundred and two patients received MAL-PDT and 198 received imiquimod. The superiority of imiquimod vs. MAL-PDT was observed in subgroups of females, sBCC on the trunk and large tumours with risk differences in favour of imiquimod of 18·4% [95% confidence interval (CI) 7·8-29·0%], 21·0% (95% CI 10·9-31·1%) and 18·9% (95% CI 7·1-30·7%), respectively. Higher probability of treatment success for imiquimod vs. MAL-PDT was consistently found in all other subgroups with the exception of sBCC localized on the lower extremities in older patients. In the latter subgroup, the risk difference at the expense of imiquimod was -57·3% (95% CI -81·7% to -32·9%). CONCLUSIONS: Imiquimod remains the first-choice treatment for sBCC in terms of effectiveness. In older patients with sBCC on the lower extremities MAL-PDT might be preferred. Results should be interpreted carefully as subgroup analyses were exploratory and not driven by prior hypotheses.

Extended haplotype studies in South African and Dutch variegate porphyria families carrying the recurrent p.R59W mutation confirm a common ancestry.

BACKGROUND: Variegate porphyria (VP) is due to a partial deficiency of protoporphyrinogen oxidase (PPOX), the seventh enzyme in the haem biosynthetic pathway. Clinically, VP is characterized by photosensitivity and acute neurovisceral attacks that can manifest separately or together in affected individuals. The disease is inherited in an autosomal dominant fashion with incomplete penetrance and PPOX gene mutations associated with VP are usually unique to patients and their families. In South Africa, however, VP is highly prevalent as the result of a founder mutation, designated p.R59W. Previous genealogical and haplotype studies showed a link between South African and Dutch carriers of p.R59W and it was suggested that this mutation was introduced to South Africa by Dutch settlers at the end of the 17th century. OBJECTIVES: To perform extended haplotype analysis in six South African and Dutch VP families with the p.R59W mutation. METHODS: Haplotyping of 13 microsatellite markers flanking the PPOX gene on chromosome 1q22-23 and five informative single nucleotide polymorphisms within and around the gene. RESULTS: A core haplotype cosegregated in all families studied. CONCLUSIONS: Our data deliver further confirmation that the South African and Dutch VP families carrying mutation p.R59W shared a common ancestor.

A novel missense mutation in GJB2, p.Tyr65His, causes severe Vohwinkel syndrome.

Gap junctions are intercellular channels which are permeable to ions and small molecules up to about 1 kDa in size. They are prominent in the skin, but their precise function there is largely unknown. Mutations in skin-expressed gap junction genes disrupt epidermal growth and differentiation. A relatively minor epidermal connexin, connexin 26 (Cx26), is associated with a wide variety of phenotypes, each specifically associated with a particular amino acid residue. How the different mutations in GJB2 lead to such distinctive phenotypes is poorly understood. Analysis of new GJB2 mutations can shed new light on pathogenesis and the apparently vital role of Cx26 in maintaining epidermal integrity.

Focal dermal hypoplasia in a male patient due to mosaicism for a novel PORCN single nucleotide deletion.

BACKGROUND: Focal dermal hypoplasia (FDH) is an X-linked dominant disorder caused by nonsense mutations and deletions in the PORCN gene coding for a transmembrane endoplasmic reticulum protein required for Wingless signalling. Symptoms consist mainly of linear atrophic skin defects, skeletal deformities and, in many cases, mental retardation. Osteopathia striata is a nearly constant feature. Approximately 90% of patients are women. A few instances of father-to-daughter transmission and a number of sporadic male cases presumably as a result of somatic mosaicism have been recorded. OBJECTIVES: The aim of this study was to demonstrate the presence of somatic mosaicism for PORCN mutations in a male patient. METHODS: We sequenced the PORCN gene in different tissues from a boy with symptoms of FDH. RESULTS: We demonstrate post-zygotic mosaicism for a novel deletion in the PORCN gene. CONCLUSIONS: A novel PORCN deletion, present in a post-zygotic mosaic, causes focal dermal hyplasia in a male patient.

Bile duct paucity is part of the neonatal ichthyosis-sclerosing cholangitis phenotype.

Neonatal ichthyosis-sclerosing cholangitis (NISCh) syndrome is a rare autosomal recessive disorder associated with scalp hypotrichosis, scarring alopecia, ichthyosis and sclerosing cholangitis. It is caused by homozygous mutations in the CLDN1 gene coding for the tight junction component claudin-1. Only five patients have been reported so far: four patients from two inbred Moroccan families, all carrying a dinucleotide deletion c.200_201delTT in the CLDN1 gene and a Swiss patient with a 1-bp deletion (c.358delG) in exon 2. Here, we report on three Moroccan brothers born of consanguineous parents (first cousins) presenting with ichthyosis, hypotrichosis and congenital paucity of bile ducts. In our patients, we found the same dinucleotide deletion (c.200_201delTT) in the CLDN1 gene that had been reported previously. In our view, this is suggestive of a founder effect. Interestingly, our patients presented not with sclerosing cholangitis but with congenital paucity of bile ducts. Although the two conditions cannot always be easily distinguished, we would suggest that paucity of bile ducts could be a manifestation of NISCh.

Cancer-related secondary lymphoedema due to cutaneous lymphangitis carcinomatosa: clinical presentations and review of literature.

Lymphoedema is a clinical condition caused by impairment of the lymphatic system, leading to swelling of subcutaneous soft tissues. As a result, accumulation of protein-rich interstitial fluid and lymphostasis often causes additional swelling, fibrosis and adipose tissue hypertrophy leading to progressive morbidity and loss of quality of life for the patient. Lymphoedema can be distinguished as primary or secondary. Lymphoedema is a complication frequently encountered in patients treated for cancer, especially after lymphadenoectomy and/or radiotherapy based on destruction of lymphatics. However, although lymphatic impairment is sometimes caused by obstructive solid metastasis, we present three cases of secondary lymphoedema with minor dermatological features without detectable solid metastasis. Sometimes this type of lymphoedema is mistakenly called malignant lymphoedema. All patients were previously treated for cancer without clinical signs of recurrence, presented with progressive lymphoedema and minor dermatological features of unknown origin. Clinical and histopathological examination of the skin revealed diffuse lymphangitis carcinomatosa, leading to secondary lymphoedema and adjustment of the therapeutic approach and prognosis. We reviewed literature on these rare presentations of cancer recurrence and recommend, where appropriate, consulting a dermatologist when discrete skin abnormalities are seen in patients with a history of cancer and developing lymphoedema.

A novel missense mutation in GJB2 disturbs gap junction protein transport and causes focal palmoplantar keratoderma with deafness.

Gap junctions are intercellular channels that mediate rapid intercellular communication. They consist of connexins, small transmembrane proteins that belong to a large family found throughout the animal kingdom. In the skin, several connexins are expressed and are involved in the regulation of epidermal growth and differentiation. One of the skin expressed gap junction genes is GJB2, which codes for connexin 26 and is associated with a wide variety of keratinisation disorders. Here, we report on a family with a novel GJB2 mutation (p.His73Arg) causing a syndrome of focal palmoplantar keratoderma with severe progressive sensorineural hearing impairment, a phenotype reminiscent of Vohwinkel syndrome. Using fluorescent connexin fusion proteins, we show that the mutation induces a transport defect similar to that found for the Vohwinkel syndrome mutation p.Asp66His. Co-transfection into cells expressing wild type connexin26 shows that the mutant has a dominant negative effect on connexin trafficking. We suggest that there may be a weak genotype-phenotype correlation for mutations in GJB2.

Schnitzler's syndrome - a novel hypothesis of a shared pathophysiologic mechanism with Waldenström's disease.

Schnitzler's syndrome is an auto-inflammatory disorder which is characterized by two mandatory features: an urticarial rash and a monoclonal gammopathy. Although the pathophysiology of this syndrome is not yet fully understood, a role for interleukin-1 seems apparent. While this presumed link between interleukin-1 and the monoclonal gammopathy is not yet elucidated, a mutual factor in pathophysiology however seems likely. Here we present a novel hypothesis of a shared pathophysiologic mechanism between Schitzler's syndrome and monoclonal gammopathy.

Granulomatous rosacea and Crohn's disease in a patient homozygous for the Crohn-associated NOD2/CARD15 polymorphism R702W.

NOD2/CARD15 belongs to the N-terminal caspase recruitment domain family of proteins involved in regulating NF-kB activation in response to inflammatory stimuli transduced through Toll-like receptors. Mutations and polymorphisms in the NOD2/CARD15 gene reduce antibacterial responses and are associated with granulomatous inflammatory conditions such as Blau syndrome and early-onset sarcoidosis. The polymorphism R702W (arginine to tryptophan) is strongly associated with susceptibility to Crohn's disease in Caucasian populations. Skin abnormalities (other than cutaneous manifestations of Crohn's disease) have not been previously associated with R702W. We report on a female patient homozygous for R702W who developed granulomatous rosacea at the age of 12 years old. From the occurrence in the context of Crohn associated with R702W, we speculate that granulomatous rosacea may be an entity distinct from other forms of rosacea, which are associated with increased production of antibacterial proteins such as cathelicidin.

Fractionated 5-aminolaevulinic acid-photodynamic therapy vs. surgical excision in the treatment of nodular basal cell carcinoma: results of a randomized controlled trial.

BACKGROUND: Skin cancer incidence rates have been increasing for decades and this increase is expected to continue. Surgical excision (SE) is the treatment of first choice for nodular basal cell carcinoma (nBCC). Photodynamic therapy (PDT) has proven to be an effective treatment for superficial basal cell carcinoma. Its long-term efficacy in nBCC has not yet been established. OBJECTIVES: Prospectively compare the efficacy of 5-aminolaevulinic acid (ALA)-PDT and SE in terms of failure rates with long-term follow-up. Determinants of failure in the study population, such as the effect of tumour depth, were analysed retrospectively. METHODS: A randomized controlled trial in 173 primary nBCCs in 149 patients. Primary nBCCs were randomly assigned either to PDT (n = 85) or to SE (n = 88). Tumours treated with PDT were illuminated twice on the same day, 4 h after application of ALA cream, 3 weeks after debulking. SE was performed under local anaesthesia with a 3-mm margin, followed by histological examination. An intention-to-treat analysis was performed. RESULTS: In total, 171 primary nBCCs in 149 patients were treated. A 3-year interim analysis revealed that the cumulative incidence of failure was 2.3% for SE and 30.3% for PDT (P < 0.001). Tumour depth and other analysed determinants of failure were not significantly related to treatment failure. CONCLUSIONS: SE proved to be significantly more effective than treatment with fractionated illumination ALA-PDT. Therefore, in the treatment of primary nBCC, SE is preferred over PDT following this treatment regimen.