Establishing and Validating an Ichthyosis Severity Index.

We designed and validated a Visual Index for Ichthyosis Severity for scale and erythema that provides (1) written descriptions of the features characteristic of each level of severity, (2) visual standards for four body sites, and (3) two distinct standards to account for different types of scale. We tested the Visual Index for Ichthyosis Severity for reliability and reproducibility using two different settings: one that utilized scoring of 60 test photographs by 10 dermatologists, and one with in-person evaluations on 85 subjects by 12 dermatologists at the Foundation for Ichthyosis and Related Skin Types conference. The validation process revealed high reliability and reproducibility for both scale and erythema. The interrater and intrarater intraclass correlation coefficients for scale were consistently near or greater than 0.7 in both settings. By contrast, the interrater reliability for erythema was higher during in-person validation compared with validation on test photographs. Our analysis indicates that the Visual Index for Ichthyosis Severity performs better in person than with photographs, an important consideration in the design of clinical trials. Power analysis predicts that a 1-point difference on this 5-step scale would be detectable with 12 subjects in each of two defined groups. This index provides a tool for clinical phenotyping and assessment of therapeutic response for many disorders of keratinization.

Expanding the Genotypic Spectrum of Bathing Suit Ichthyosis.

Importance: Bathing suit ichthyosis (BSI) is a rare congenital disorder of keratinization characterized by restriction of scale to sites of relatively higher temperature such as the trunk, with cooler areas remaining unaffected. Fewer than 40 cases have been reported in the literature. Bathing suit ichthyosis is caused by recessive, temperature-sensitive mutations in the transglutaminase-1 gene (TGM1). Clear genotype-phenotype correlations have been difficult to establish because several of the same TGM1 mutations have been reported in BSI and other forms of congenital ichthyosis. We identify novel and recurrent mutations in 16 participants with BSI. Objective: To expand the genotypic spectrum of BSI, identifying novel TGM1 mutations in patients with BSI, and to use BSI genotypes to draw inferences about the temperature sensitivity of TGM1 mutations. Design, Setting, and Participants: A total of 16 participants with BSI from 13 kindreds were identified from 6 academic medical centers. A detailed clinical history was obtained from each participant, including phenotypic presentation at birth and disease course. Each participant underwent targeted sequencing of TGM1. Main Outcomes and Measures: Phenotypic and genotypic characteristics in these patients from birth onward. Results: Of the 16 participants, 7 were male, and 9 were female (mean age, 12.6 years; range, 1-39 years). We found 1 novel TGM1 indel mutation (Ile469_Cys471delinsMetLeu) and 8 TGM1 missense mutations that to our knowledge have not been previously reported in BSI: 5 have been previously described in non-temperature-sensitive forms of congenital ichthyosis (Arg143Cys, Gly218Ser, Gly278Arg, Arg286Gln, and Ser358Arg), and 3 (Tyr374Cys, Phe495Leu, and Ser772Arg) are novel mutations. Three probands were homozygous for Arg264Trp, Arg286Gln, or Arg315Leu, indicating that these mutations are temperature sensitive. Seven of 10 probands with a compound heterozygous TGM1 genotype had a mutation at either arginine 307 or 315, providing evidence that mutations at these sites are temperature sensitive and highlighting the importance of these residues in the pathogenesis of BSI. Conclusions and Relevance: Our findings expand the genotypic spectrum of BSI and the understanding of temperature sensitivity of TGM1 mutations. Increased awareness of temperature-sensitive TGM1 genotypes should aid in genetic counseling and provide insights into the pathophysiology of TGM1 ichthyoses, transglutaminase-1 enzymatic activity, and potential therapeutic approaches.

Palmoplantar Keratoderma in Costello Syndrome Responsive to Acitretin.

Costello syndrome (CS) is a multisystem congenital disorder characterized by coarse facial features, cardiac defects, intellectual disability, and predisposition to malignancies. Dermatologic findings can include cutaneous papillomas, skin redundancy, acanthosis nigricans, and keratosis pilaris. Palmoplantar keratoderma (PPK) is present in approximately 76% of patients with CS, with disabling functional consequences in severe cases. We report a case of CS with severe PPK that improved dramatically with systemic administration of acitretin 0.3 mg/kg/day.

Recent advances in understanding ichthyosis pathogenesis.

The ichthyoses, also known as disorders of keratinization (DOK), encompass a heterogeneous group of skin diseases linked by the common finding of abnormal barrier function, which initiates a default compensatory pathway of hyperproliferation, resulting in the characteristic clinical manifestation of localized and/or generalized scaling. Additional cutaneous findings frequently seen in ichthyoses include generalized xerosis, erythroderma, palmoplantar keratoderma, hypohydrosis, and recurrent infections. In 2009, the Ichthyosis Consensus Conference established a classification consensus for DOK based on pathophysiology, clinical manifestations, and mode of inheritance. This nomenclature system divides DOK into two main groups: nonsyndromic forms, with clinical findings limited to the skin, and syndromic forms, with involvement of additional organ systems. Advances in next-generation sequencing technology have allowed for more rapid and cost-effective genetic analysis, leading to the identification of novel, rare mutations that cause DOK, many of which represent phenotypic expansion. This review focuses on new findings in syndromic and nonsyndromic ichthyoses, with emphasis on novel genetic discoveries that provide insight into disease pathogenesis.