A cross-sectional study of erythromelalgia in patients with pachyonychia congenita

Pachyonychia congenita (PC) is a rare genodermatosis characterised by focal palmoplantar keratoderma, severe plantar pain, dystrophic nails. Anecdotally, some PC patients have erythematous soles and episodic burning plantar pain, indicative of secondary erythromelalgia. This study aimed to identify the prevalence and genetic predictors of erythromelalgia in PC.

Walking a day in a pachyonychia congenita patient's shoes: Impact on plantar pain and activity levels measured with wristband activity trackers

Background Plantar keratoderma is a common finding in pachyonychia congenita, significantly impairing ambulation and quality of life. Due to the variation of pain reporting in pachyonychia congenita clinical studies, it is difficult to evaluate the efficacy of treatment outcomes for painful plantar keratodermas. Objectives To objectively analyse associations between plantar pain and activity levels in pachyonychia congenita patients using a wristband tracker. Methods Pachyonychia congenita patients and matched normal controls wore wristband activity trackers and completed a daily digital survey to record their highest and total pain scores (0-10 scale) each day for 28 consecutive days during four different seasons. Results Twenty four participants (12 pachyonychia congenita patients and 12 matched normal controls) completed the study. Pachyonychia congenita patients walked 1801.30 fewer steps/day (95% CI, -3666.4, 64.1) than normal controls (P = 0.072) and had greater average total [5.26; SD, 2.10] and highest (6.92; SD, 2.35) daily pain than normal controls [0.11 (SD, 0.47), 0.30 (SD, 0.22), respectively] (P < 0.001, both). On average, for each one unit increase in daily highest pain level, pachyonychia congenita activity decreased 71.54 steps/day (SE, 38.90, P = 0.066). Limitation The study had a small number of participants, limiting statistical power. Only pachyonychia congenita patients, ages 18 years or older, with keratin 6a, keratin 16, and keratin 17 mutations were included, limiting generalizability. Conclusion Pachyonychia congenita patients were less active with significantly higher pain than normal controls. There was an inverse correlation between pain and activity. Our findings suggest that wristband tracker technology may be used to evaluate treatment efficacy in future trials on severe plantar pain; therapeutic interventions that decrease plantar pain should correlate with significant increases in activity using wristband trackers.

Identification of clinically useful predictive genetic variants in pachyonychia congenita

BACKGROUND

Pachyonychia congenita (PC) refers to a group of autosomal dominant disorders caused by mutations in five keratin genes (KRT16,KRT6A,KRT17,KRT6B or KRT6C). Current disease classification is based on the gene harbouring disease-causing variants.

AIMS

We harnessed the International Pachyonychia Congenita Research Registry (IPCRR) containing both clinical and molecular data on patients with PC worldwide, to identify genetic variants predicting disease severity.

METHODS

We ascertained 815 individuals harbouring keratin mutations registered in the IPCRR. We looked for statistically significant associations between genetic variants and clinical manifestations in a subgroup of patients carrying mutations found in at least 10% of the cohort. Data were analysed using χ² and Kruskal-Wallis tests.

RESULTS

We identified five mutations occurring in at least 10% of the patients registered in the IPCRR. The KRT16 p.L132P mutation was significantly associated with younger age of onset, presence of palmar keratoderma oral leucokeratosis and a higher number of involved nails. By contrast, the KRT16 p.N125S and p.R127C mutations resulted in a milder phenotype featuring a decreased number of involved nails and older age of onset. Patients carrying the p.N125S mutation were less likely to develop palmar keratoderma while p.R127C was associated with an older age of palmoplantar keratoderma onset. Moreover, the KRT17 p.L99P mutation resulted in an increased number of involved fingernails and patients demonstrating 20-nail dystrophy, while the opposite findings were observed with KRT17 p.N92S mutation.

CONCLUSIONS

We have identified novel and clinically useful genetic predictive variants in the largest cohort of patients with PC described to date.

The histopathological features of the nail plate in pachyonychia congenita

BACKGROUND

Pachyonychia congenita (PC) is a rare autosomal dominant disorder of keratinization mediated by genetic mutations in KRT6A, KRT6B, KRT6C, KRT16, or KRT17. While nail dystrophy in PC has a significant impact on quality of life, the histopathological features of the nail plate in PC have not been previously reported. We report the histopathological features of nail plates provided by 19 patients with genetically confirmed PC.

METHODS

Nineteen patients with genetically confirmed PC provided a total of 56 nail plates for histopathologic examination. The nail plates were examined for the presence of hyphae, yeast, bacteria, neutrophils, parakeratosis, plasma globules, and hemorrhage. Specimens with onychomycosis (three patients) were excluded from the analysis.

RESULTS

No specific histopathological feature was identified in PC nails. Parakeratosis and plasma globules were the most prominent features in both clinically affected and unaffected PC nails. There was a significant association between clinical dystrophy of all 20 nails and KRT6A mutations, and a lack of dystrophy of all 20 nails in KRT6B mutations.

CONCLUSIONS

Parakeratosis and plasma globules in the absence of other inflammatory disorders should raise PC in the histopathologic differential diagnosis. The presence of onychomycosis in a nail plate does not exclude a diagnosis of PC.

Symptomatic mucosal involvement in pachyonychia congenita: challenges in infants and young children

BACKGROUND

Pachyonychia congenita (PC) is a rare autosomal dominant genodermatosis caused by a mutation in any one of five keratin genes (KRT6A, KRT6B, KRT6C, KRT16 or KRT17). Characteristic features of PC are painful palmoplantar keratoderma, variable nail dystrophy, cysts, follicular hyperkeratosis and often oral leukokeratosis. Although oral leukokeratosis can go unnoticed, mucosal involvement of the oral cavity and upper airways can manifest with pain during feeding, hoarseness, stridor and, occasionally, life-threatening obstruction.

OBJECTIVES

To characterize patients with PC with symptomatic mucosal involvement.

METHODS

We present a case series of nine children with PC with symptomatic mucosal involvement, all with heterozygous mutations in KRT6A. Seven patients complained of painful feeding problems. Four patients were diagnosed with failure to thrive, three of whom required a feeding tube. Simple feeding solutions were beneficial in most cases. Seven patients had laryngeal involvement and one patient died at 4 years of age from acute laryngeal obstruction.

CONCLUSIONS

It is important for dermatologists and otolaryngologists to be aware that symptomatic mucosal involvement, and very rarely laryngeal obstruction, can occur in patients with PC. Usually simple feeding solutions may prevent complications and failure to thrive. What's already known about this topic? Pachyonychia congenita (PC) is a rare autosomal dominant genodermatosis due to a mutation in any one of five keratin genes. Symptomatic mucosal involvement is an important clinical feature of PC and appears to be more pronounced in KRT6A mutation carriers. Only leukokeratosis is frequently seen in PC and can be one of the earliest signs of disease. Laryngeal involvement is a less common feature. It might be symptomatic but usually presents as hoarseness, stridor and, occasionally, as a life-threatening respiratory distress. What does this study add? In most cases of laryngeal involvement, there is no need for any intervention. Although pain and feeding difficulties are usually attributed to the oral leukokeratosis, they can be related to a phenomenon called 'first bite syndrome' (FBS). Symptomatic mucosal involvement with feeding difficulty is important but can be managed in most cases with simple feeding solutions (e.g. softer nipple with a larger hole, thicker formula and feeding with a syringe). Linked Comment: Youssefian and Vahidnezhad. Br J Dermatol 2020; 182:536-537.

Comparing fatal occupational accidents in Denmark and Sweden 1993–2012

Background

Denmark and Sweden are in many respects two very similar countries with similar welfare state systems and work environment authorities. Nevertheless, marked differences in the incidence of fatal occupational accidents have been found in earlier comparisons of the two countries.

Aims

To investigate differences in the incidence of fatal occupational accidents in the period from 1993 to 2012 to establish to what extent characteristics of the deceased can explain some of the difference between the two countries.

Methods

Analyses of the accident registers of the two countries’ national work environment authorities with supplemental linkages to official registers on employment status are used to determine the incidence of fatal occupational accidents for different groups. The analysis is based on 2375 accidents (1068 in Denmark and 1307 in Sweden) over the period of 20 years. Poisson regression is used to derive incidence rates over time for specific groups.

Results

In the study period, the incidence of fatal occupational accidents decreased in both countries (incidence rate ratio [IRR]: 0.95), although the incidence was on average higher in Denmark (IRR: 1.20) and grew larger over time. This difference did not disappear after adjusting for age, sex and industry among the deceased (IRR: 1.12).

Conclusions

The incidence of fatal occupational accidents was slightly higher in Denmark in the entire period. The difference could not be explained completely by sociodemographic differences or differences related to the labour market structure in the two countries, i.e. other factors (e.g. cultural) may play a role in producing the difference.

Isolated recessive nail dysplasia caused by FZD6 mutations: report of three families and review of the literature

Congenital abnormalities of the nail are rare conditions that are most frequently associated with congenital ectodermal syndromes involving several of the epidermal appendages including the skin, teeth, hair and nails. Isolated recessive nail dysplasia (IRND) is much rarer but has recently been recognized as a condition resulting in 20‐nail dystrophy in the absence of other cutaneous or extracutaneous findings. A few case reports have identified mutations in the Frizzled 6 (FZD6) gene in families presenting with abnormal nails consistent with IRND. These reports have highlighted the role of Wnt–FZD signalling in the process of nail formation. We report three families presenting with features of IRND, in whom we identified mutations in FZD6, including one previously unreported mutation.

The molecular genetic analysis of the expanding pachyonychia congenita case collection

BACKGROUND

Pachyonychia congenita (PC) is a rare autosomal dominant keratinizing disorder characterized by severe, painful, palmoplantar keratoderma and nail dystrophy, often accompanied by oral leucokeratosis, cysts and follicular keratosis. It is caused by mutations in one of five keratin genes: KRT6A, KRT6B, KRT6C, KRT16 or KRT17.

OBJECTIVES

To identify mutations in 84 new families with a clinical diagnosis of PC, recruited by the International Pachyonychia Congenita Research Registry during the last few years.

METHODS

Genomic DNA isolated from saliva or peripheral blood leucocytes was amplified using primers specific for the PC-associated keratin genes and polymerase chain reaction products were directly sequenced.

RESULTS

Mutations were identified in 84 families in the PC-associated keratin genes, comprising 46 distinct keratin mutations. Fourteen were previously unreported mutations, bringing the total number of different keratin mutations associated with PC to 105.

CONCLUSIONS

By identifying mutations in KRT6A, KRT6B, KRT6C, KRT16 or KRT17, this study has confirmed, at the molecular level, the clinical diagnosis of PC in these families.

Intractable localized pruritus as the sole manifestation of intramedullary tumor in a child: case report and review of the literature

IMPORTANCE

Persistent localized pruritus is a rare manifestation of central nervous system tumors. Delayed diagnosis can lead to devastating complications.

OBSERVATIONS

We report an otherwise healthy 19-month-old girl who presented with signs of localized intractable pruritus of 6 months' duration on the left side of the neck, shoulder, and arm, resistant to systemic antihistamines and topical corticosteroids. Findings from skin biopsy, viral culture for varicella-zoster virus, and skin prick test to common food and animal allergens were nondiagnostic. Neurologic examination results were unremarkable. After several months of localized intractable pruritus, magnetic resonance imaging of the cervical spine with and without contrast was performed, which revealed an intramedullary spinal cord tumor extending from just above the foramen magnum to C6. The tumor was surgically resected and found to be a ganglioglioma. Within a week after the surgery her pruritus completely resolved.

CONCLUSIONS AND RELEVANCE

We recommend a detailed neurologic examination in any case of persistent localized pruritus, in the absence of primary dermatologic causes. Given the challenges of performing a reliable neurologic examination in children, neuroimaging might be considered in children with intractable localized pruritus of unknown etiology of the head and neck or upper extremity, even in the absence of focal neurologic deficits.

Transgrediens pachyonychia congenita (PC): case series of a nonclassical PC presentation

BACKGROUND

Pachyonychia congenita (PC) is a rare keratin disorder that typically presents with nail dystrophy and focal plantar keratoderma. We present seven cases of PC with transgrediens involvement of the dorsal feet.

OBJECTIVES

To document the extension of their disease to the dorsum of the feet in patients with mutation-confirmed PC, to report the natural history of PC with such transgrediens involvement, to generate hypotheses regarding aetiology, and to suggest prevention and treatment modalities.

METHODS

Genetically confirmed cases of PC with transgrediens foot involvement were verified through the International Pachyonychia Congenita Research Registry (IPCRR) and characterized via telephone survey and photography.

RESULTS

Seven patients with PC in the IPCRR were confirmed to have transgrediens lesions on the dorsal feet (six KRT6A mutations; one KRT16 mutation). Six cases had pre-existing nontransgrediens keratoderma and all cases reported standing, wearing shoes, foot moisture, and/or infection as exacerbating or predisposing factors. Improvement, reported in six cases, was attributed to use of antibiotics or gentian violet, or improved footwear.

CONCLUSIONS

Transgrediens involvement of the dorsal feet is a rare manifestation of mutation-confirmed PC and may be more common in patients who carry a KRT6A mutation. Trauma, friction, infection and wound healing may exacerbate or predispose toward transgrediens lesions. It remains to be proven whether transgrediens-associated infection is causal or represents a primary or secondary process. Patients with PC who develop transgrediens lesions may benefit from fungal and bacterial cultures, followed by appropriate antimicrobial treatments. Efforts to decrease skin friction and moisture may also improve and/or prevent transgrediens spread.

Physically-Based Interactive Flow Visualization Based on Schlieren and Interferometry Experimental Techniques

Understanding fluid flow is a difficult problem and of increasing importance as computational fluid dynamics (CFD) produces an abundance of simulation data. Experimental flow analysis has employed techniques such as shadowgraph, interferometry, and schlieren imaging for centuries, which allow empirical observation of inhomogeneous flows. Shadowgraphs provide an intuitive way of looking at small changes in flow dynamics through caustic effects while schlieren cutoffs introduce an intensity gradation for observing large scale directional changes in the flow. Interferometry tracks changes in phase-shift resulting in bands appearing. The combination of these shading effects provides an informative global analysis of overall fluid flow. Computational solutions for these methods have proven too complex until recently due to the fundamental physical interaction of light refracting through the flow field. In this paper, we introduce a novel method to simulate the refraction of light to generate synthetic shadowgraph, schlieren and interferometry images of time-varying scalar fields derived from computational fluid dynamics data. Our method computes physically accurate schlieren and shadowgraph images at interactive rates by utilizing a combination of GPGPU programming, acceleration methods, and data-dependent probabilistic schlieren cutoffs. Applications of our method to multifield data and custom application-dependent color filter creation are explored. Results comparing this method to previous schlieren approximations are finally presented.

An appraisal of oral retinoids in the treatment of pachyonychia congenita

BACKGROUND

Pachyonychia congenita (PC), a rare autosomal-dominant keratin disorder caused by mutations in keratin genes KRT6A/B, KRT16, or KRT17, is characterized by painful plantar keratoderma and hypertrophic nail dystrophy. Available studies assessing oral retinoid treatment for PC are limited to a few case reports.

OBJECTIVE

We sought to assess overall effectiveness, adverse effects, and patient perspective in patients with PC receiving oral retinoids.

METHODS

In a questionnaire-based retrospective cross-sectional survey of 30 patient with PC assessing oral retinoids (10-50 mg/d for 1-240 months), we determined the clinical score, satisfaction score, visual analog pain scale, and adverse effects.

RESULTS

In 50% of patients there was thinning of hyperkeratoses (average improvement 1.6 on a scale from -3 to +3) (95% confidence interval 1.2-1.9, P < .001). In all, 14% observed amelioration of their pachyonychia; 79% did not experience any nail change. The self-reported overall satisfaction score with oral retinoid treatment was 2 or greater in 50% of the patients (mean 4.5 on a scale of 1-10). Although 33% reported decreased and 27% increased plantar pain with treatment, 40% did not notice any pain change. All patients experienced adverse effects, and 83% reported to have discontinued medication. Risk/benefit analysis favored lower retinoid doses (≤25 mg/d) over a longer time period (>5 months), compared with higher doses (>25 mg/d) for a shorter time (≤5 months).

LIMITATIONS

The retrospective, cross-sectional study design is prone to a recall bias.

CONCLUSION

Oral retinoids are effective in some patients with PC. However, many patients discontinued medication because adverse effects outweighed the benefits. Careful dose titration is warranted in patients informed about potential adverse effects.

The phenotypic and molecular genetic features of pachyonychia congenita

Pachyonychia congenita (PC) is an autosomal dominant genodermatosis caused by heterozygous mutations in any one of the genes encoding the differentiation-specific keratins K6a, K6b, K16, or K17. The main clinical features of the condition include painful and highly debilitating plantar keratoderma, hypertrophic nail dystrophy, oral leukokeratosis, and a variety of epidermal cysts. Although the condition has previously been subdivided into PC-1 and PC-2 subtypes, the phenotypic characterization of 1,000 mutation-verified PC patients enrolled in the International PC Research Registry, coordinated by the patient advocacy group PC Project, shows that there is considerable overlap between these subtypes. Thus, a new genotypic nomenclature is proposed, in which PC-6a represents a patient carrying a mutation in the K6a gene, etc. Although a rare disorder, PC represents a good model for therapy development, and international efforts are ongoing to develop and deliver siRNA, gene, correction, small molecule, and other strategies to treat this painful, disabling skin condition. The special relationship between PC Project and the PC research community has greatly accelerated the development pathway from gene identification to clinical trials in only a few years and represents a paradigm of hope for other orphan diseases.

Sick at work--a risk factor for long-term sickness absence at a later date?

BACKGROUND

Little is known about the long-term consequences of sickness presence (ie, going to work despite ill-health), although one study suggests an association with coronary heart disease. This study examined the effect of sickness presence on future long-term sickness absence.

METHODS

Information from a random sample of 11 838 members of the Danish core workforce was collected from questionnaires, containing questions about work, family and attitudes towards sickness absence. Information on prospective sickness absence spells of at least 2 weeks was derived from an official register during a follow-up period of 1.5 years.

RESULTS

Sickness presence is associated with long-term sickness absence of at least 2 weeks' duration as well as with spells lasting at least 2 months. Participants who had gone to work ill more than six times in the year prior to baseline had a 74% higher risk of becoming sick-listed for more than 2 months, even when controlling for a wide range of potential confounders as well as baseline health status and previous long-term sickness absence. The association was consistent for most subgroups of employees reporting various symptoms, but either disappeared or became insignificant when analysing subgroups of employees with specific chronic diseases.

CONCLUSIONS

Going to work ill repeatedly is associated with long-term sickness absence at a later date. For this reason, researchers and policy-makers should consider this phenomenon more carefully when planning future studies of sickness absence or when laying out new policies.

Lesions resembling malignant atrophic papulosis in a patient with progressive systemic sclerosis

Malignant atrophic papulosis (MAP), or Degos syndrome, is a rare disorder of unknown etiology. It is characterized by a deep subcutaneous vasculopathy resulting in atrophic, porcelain-white papules. We report the case of a 42-year-old woman with a history of progressive systemic sclerosis who presented with painful subcutaneous nodules on her abdomen along with chronic atrophic papules on her upper and lower limbs. Biopsy results of both types of lesions revealed vascular thrombi without surrounding inflammation. We briefly review the literature on MAP and its association with various connective tissue diseases. To our knowledge, there have been no previous reports of a patient with the clinical and histologic presentations described here. Although the histologic appearance of the subcutaneous nodules was very similar to that of the atrophic papules, the clinical characteristics of the 2 types of lesions were strikingly different. It is fair to theorize that Degos lesions do not start as atrophic porcelain-white papules but rather evolve from a primary lesion. We hypothesize that these lesions start as painful red nodules and may represent part of the disease spectrum in the evolution of MAP.