Two novel recessive mutations in KRT14 identified in a cohort of 21 Spanish families with epidermolysis bullosa simplex

BACKGROUND

Basal epidermolysis bullosa simplex (EBS) is a group of blistering genodermatoses mostly caused by mutations in the keratin genes, KRT5 and KRT14. Recessive mutations represent about 5% of all EBS mutations, being common and specific in populations with high consanguinity, where affected patients show severe phenotypes.

OBJECTIVES

To accomplish the first mutational analysis in patients of Spanish origin with EBS and to delineate a comprehensive genotype-phenotype correlation.

METHODS

Twenty-one EBS families were analysed. Immunofluorescence mapping at the dermoepidermal junction level was performed on skin biopsies from patients. Mutation screening of the entire coding sequences of KRT5 and KRT14 in genomic DNA was assessed by polymerase chain reaction and direct sequencing.

RESULTS

KRT5 or KRT14 causative mutations were identified in 18 of the 21 EBS families. A total of 14 different mutations were disclosed, of which 12 were dominant missense mutations and two truncating recessive mutations. Five of the 14 mutations were novel including three dominant in KRT5 (p.V186E, p.T321P and p.A428T) and two recessive in KRT14 (p.K116X and p.K250RfsX8). The two patients with EBS carrying homozygous recessive mutations were affected by severe phenotypes and belonged to consanguineous families. All five families with the EBS Dowling-Meara subtype carried recurrent mutations affecting the highly conserved ends of the α-helical rod domain of K5 and K14. The seven mutations associated with the localized EBS subtype were widely distributed along the KRT5 and KRT14 genes. Two families with mottled pigmentation carried the P25L mutation in KRT5, commonly associated with this subtype.

CONCLUSIONS

This study further confirms the genotype-phenotype correlation established for EBS in other ethnic groups, and is the first in a Mediterranean country (excluding Israel). This study adds two novel recessive mutations to the worldwide record to date, which includes a total of 14 mutations. As in previous reports, the recessive mutations resulted in a lack of keratin K14, giving rise to a generalized and severe presentation.

Rod photopigment deficits in albinos are specific to mammals and arise during retinal development

Adult albino mammals have specific retinal defects, including reduced numbers of rod photoreceptors. To examine when this rod deficit arises and whether it exists in nonmammalian albinos, we have used absorbance spectrophotometry to measure photopigment levels in dark-adapted eyes taken from three groups of pigmented and albino animals: adult rodents (rats and mice), developing rats, and mature Xenopus frogs. Rhodopsin concentrations were consistently and significantly reduced in mammalian albinos compared to their wild-type counterparts from before the time of eye opening, but photopigment levels were similar in frogs of both pigmentation phenotypes. The results strongly suggest that deficits in the rod cell population arise early in development of the mammalian albino retina, but do not generalize to nonmammalian mutants lacking retinal melanin.

Toenail onychomycosis in patients with acquired immune deficiency syndrome: treatment with terbinafine

Skin infections caused by dermatophytes are one of the most frequent dermatological complications in patients with acquired immunodeficiency syndrome (AIDS) resulting from infection with human immunodeficiency virus (HIV). Tinea unguium associated with AIDS is characterized by being clinically more aggressive and therapeutically more difficult to treat than in the general population. Terbinafine is considered to be a first-choice option for the treatment of dermatophyte onychomycosis in immunocompetent individuals. This drug has been used in a series of 21 HIV-positive patients diagnosed with tinea unguium for 1 year in the University Hospital La Paz, Madrid. All patients underwent a subsequent clinical follow-up for 6 months. The results showed a high percentage of clinical and mycological cures, as well as maintenance of the response after follow-up; no drug interactions or significant adverse effects related to the drug under study were recorded.

High incidence of porokeratosis in renal transplant recipients

Immunosuppression is a well-documented precipitant of porokeratosis (PK). However, PK is not considered among the most common cutaneous disorders in immunosuppressed patients. We studied prospectively a series of 103 renal transplant patients and found 11 cases (10.68%) of PK. Our series represents the highest incidence of PK in transplant patients reported so far. Our findings suggest that PK in transplant recipients may be more frequent than previously thought.