Pachyonychia Congenita: A Research Agenda Leading to New Therapeutic Approaches

Pachyonychia congenita (PC) is a dominantly inherited genetic disorder of cornification. PC stands out among other genodermatoses because despite its rarity, it has been the focus of a very large number of pioneering translational research efforts over the past 2 decades, mostly driven by a patient support organization, the Pachyonychia Congenita Project. These efforts have laid the ground for innovative strategies that may broadly impact approaches to the management of other inherited cutaneous and noncutaneous diseases. This article outlines current avenues of research in PC, expected outcomes, and potential hurdles.

Phenotype and genotype features of Vietnamese children with pachyonychia congenita

BACKGROUND

Pachyonychia congenita (PC) is a group of autosomal dominant disorders caused by mutations in one of five keratin genes (KRT6A, KRT6B, KRT6C, KRT16, or KRT17). PC is an extremely rare condition. To our knowledge, this is the largest genotype-phenotype study of PC in a Vietnamese population to date.

MATERIALS AND METHODS

We investigated keratin gene mutations and clinical features of seven Vietnamese children with PC.

RESULTS

The seven Vietnamese patients were from six different families (two patients in the same family) from across Northern, Central, and Southern Vietnam. All children displayed PC symptoms before 1 year of age, but diagnosis was delayed in 4/7 patients. Thick fingernails, thick toenails, oral leukokeratosis, and follicular hyperkeratosis were the most common features recorded by all seven patients. Plantar keratoderma and thick fingernails were the clinical features associated with the most significant effect on daily function. All patients had mutations in KRT6A (PC-K6a) focused on the 1A and 2B domains. We found three distinct types of mutations (K6a R466P, K6a N171K, and K6a N172del). One mutation (N172del) was common to 5/7 (71.4%) of the patients.

CONCLUSIONS

Individuals displaying nail dystrophy, oral leukokeratosis, follicular hyperkeratosis, and plantar keratoderma should be referred for genetic testing given the high likelihood of a PC-K6a-related mutation in patients with this constellation of clinical signs.

Questionnaire Modifications and Alternative Scoring Methods of the Dermatology Life Quality Index: A Systematic Review

OBJECTIVES

Dermatology Life Quality index (DLQI) is the most widely used health-related quality of life questionnaire in dermatology. Little is known about existing questionnaire or scoring modifications of the DLQI. We aimed to systematically review, identify, and categorize all modified questionnaire versions and scoring methods of the DLQI.

METHODS

We performed a systematic literature search in PubMed, Web of Science, CINAHL, and PsychINFO. Methodologic quality and evidence of psychometric properties were assessed using the Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN) and Terwee checklists.

RESULTS

The included 81 articles reported on 77 studies using 59 DLQI modifications. Modifications were used for a combined sample of 25 509 patients with 47 different diagnoses and symptoms from 28 countries. The most frequently studied diseases were psoriasis, hirsutism, acne, alopecia, and bromhidrosis. The modifications were categorized into the following nonmutually exclusive groups: bolt-ons or bolt-offs (48%), disease, symptom, and body part specifications (42%), changes in existing items (34%), scoring modifications (27%), recall period changes (19%), response scale modifications (15%), and illustrations (3%). The evidence concerning the quality of measurement properties was heterogeneous: 4 of 13 studies were rated positive on internal consistency, 1 of 3 on reliability, 3 of 5 on content validity, 9 of 22 on construct validity, 6 of 6 on criterion validity, and 1 of 1 on responsiveness.

CONCLUSION

An exceptionally large number of DLQI modifications have been used that may indicate an unmet need for adequate health-related quality of life instruments in dermatology. The psychometric overview of most questionnaire modifications is currently incomplete, and additional efforts are needed for proper validation.

Disease-specific health related quality of life patient reported outcome measures in Genodermatoses: a systematic review and critical evaluation

Background

Health Related Quality of Life (HR-QoL) Patient reported outcome measures (PROMs) have high utility in evaluation of new interventions in genodermatoses, however inconsistent standards of development and validation have hampered widespread acceptance and adoption.

Objectives

To identify all published HR-QoL PROMs in genodermatoses and critically evaluate their development and measurement properties.

Methods

This systematic review was registered with PROSPERO (CRD42016053301). Ovid Medline, Embase and PsycINFO databases were utilised for literature review using predefined inclusion and exclusion criteria. PROM development was assessed using the COSMIN Checklist and measurement properties were assessed against quality criteria for measurement properties of health standard questionnaires.

Results

15 HRQoL PROMs in genodermatoses were identified. Major areas of deficiency in development were internal consistency, reliability and structural validity. No PROM satisfied measurement property standards for agreement, responsiveness or floor and ceiling effects. Four PROMs included Minimal Important Change scores for interpretability. Issues regarding the generalisability of the evaluated PROMs in culturally diverse and paediatric populations remain unresolved.

Conclusions

The overall standards of development and measurement properties in PROMs in genodermatoses is fair, despite no single instrument meeting all requirements. None are perfectly validated according to COSMIN criteria but seven of the fifteen PROMs may be appropriate pending further validation. The development of culturally appropriate and child-specific variants of PROMs should be a priority in order to increase the utility of patient based outcome measures in genodermatoses in various patient populations.

Electronic supplementary material

The online version of this article (10.1186/s13023-017-0739-5) contains supplementary material, which is available to authorized users.