Clinicopathological features of a suspected case of hereditary benign intraepithelial dyskeratosis with bilateral corneas involved: a case report and mini review

Genetic predisposition to ocular surface disorders and opportunities for gene-based therapies

The ocular surface, comprised of the corneal and conjunctival epithelium, innervation system, immune components, and tear-film apparatus, plays a key role in ocular integrity as well as comfort and vision. Gene defects may result in congenital ocular or systemic disorders with prominent ocular surface involvement. Examples include epithelial corneal dystrophies, aniridia, ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome, xeroderma pigmentosum (XP), and hereditary sensory and autonomic neuropathy. In addition, genetic factors may interact with environmental risk factors in the development of several multifactorial ocular surface disorders (OSDs) such as autoimmune disorders, allergies, neoplasms, and dry eye disease. Advanced gene-based technologies have already been introduced in disease modelling and proof-of-concept gene therapies for monogenic OSDs. For instance, patient-derived induced pluripotent stem cells have been used for modelling aniridia-associated keratopathy (AAK), XP, and EEC syndrome. Moreover, CRISPR/Cas9 genome editing has been used for disease modelling and/or gene therapy for AAK and Meesmann's epithelial corneal dystrophy. A better understanding of the role of genetic factors in OSDs may be helpful in designing personalized disease models and treatment approaches. Gene-based approaches in monogenic OSDs and genetic predisposition to multifactorial OSDs such as immune-mediated disorders and neoplasms with known or possible genetic risk factors has been seldom reviewed. In this narrative review, we discuss the role of genetic factors in monogenic and multifactorial OSDs and potential opportunities for gene therapy.

Case Series of Patients With Hereditary Benign Intraepithelial Dyskeratosis

PURPOSE

The purpose of this retrospective case series was to compare the outcomes of different treatment options for patients diagnosed with hereditary benign intraepithelial dyskeratosis (HBID).

METHODS

The study is designed as a single-institution retrospective chart review of patients who were clinically diagnosed with HBID during their care at the Duke Eye Center. Patient demographics were obtained, and disease course after different therapies was analyzed.

RESULTS

Seventeen patients were diagnosed with HBID. 52.9% (9/17) of patients identified with HBID reported Native American ancestry. Medical therapy alone failed to reduce the size or number of corneal lesions in any patient identified in this study. Ten of the 17 patients required surgical intervention. Two eyes received corneal biopsies, 3 eyes received a full conjunctival lesion excision with amniotic membrane grafting, 12 eyes received superficial keratectomy with amniotic membrane grafting, and 1 eye received keratoprosthesis. Lesion recurrence was seen in 9 of the 10 patients treated with surgical excision with an average time to recurrence of 1.5 and 2 months for conjunctival excisions and superficial keratectomy, respectively, when excluding patients who missed scheduled postoperative follow-up appointments.

CONCLUSIONS

Hereditary benign intraepithelial dyskeratosis is a rare and poorly understood disorder that predominantly affects people with Native American ancestry. Medical therapy only provides symptomatic relief, and patients who receive surgical excision almost always develop recurrence. As a result, we recommend future investigations focus on identifying the optimal surgical technique and timing to limit the morbidity of HBID and improve outcomes.

Genetic and developmental disorders of the oral mucosa: Epidemiology; molecular mechanisms; diagnostic criteria; management

A large number of disorders may affect the oral cavity, including genetic diseases, infections, cancers, blood diseases, skin diseases, endocrine and metabolic disorders, autoimmune and rheumatologic diseases, local lesions, to name a few. Oral mucosa shows a considerable variation in its normal structure and a wide range of conditions may affect it. Such conditions are often harmless or minor and could be primary or secondary to systemic disease. Several of them are quite rare and, hence, the diagnosis is not easy. Clinically, lesions may appear as ulcers, discoloration of the oral mucosa and alterations in size and configuration of oral anatomy. Genetic disorders have specific manifestations and can be caused by a derangement of one or more components of the tissue. Many of them follow the skin or systemic signs of the underlying genetic disease, but in a few cases oral signs could be the first manifestation of the disorder. Among them genodermatoses are prominent. They are inherited disorders characterized by a multisystem involvement. This review describes chondro-ectodermal dysplasia, dyskeratosis congenita, Ehlers-Danlos syndrome, hereditary benign intraepithelial dyskeratosis, keratosis follicularis, lipoid proteinosis, multiple hamartoma syndrome, pachyonychia congenita, Peutz-Jeghers syndrome, tuberous sclerosis and white sponge nevus. Other genetic disorders not included in the genodermatosis group and reported in the present review are: acanthosis nigricans, angio-osteo-hypertrophic syndrome, encephalotrigeminal angiomatosis, familial adenomatous polyposis, focal dermal hypoplasia, focal palmoplantar and oral mucosa hyperkeratosis syndrome, gingival fibromatosis, Maffucci's syndrome, neurofibromatosis (type 1) and oro-facial-digital syndrome (type 1). Disorders during embryonic development might lead to a wide range of abnormalities in the oral cavity; some of them are quite common but of negligible concern, whereas others are rare but serious, affecting not only the oral mucosa, but also other structures of the oral cavity (ie palate, tongue and gingiva). Fordyce's granules, leukoedema, cysts of the oral mucosa in newborns, retrocuspid papilla, geographic tongue, fissured tongue, median rhomboid glossitis, hairy tongue, lingual varices and lingual thyroid nodule are described. This review may help dentists, dental hygienists, but also general internists and pediatricians to diagnose different disorders of the oral mucosa, to understand the pathogenesis and to schedule a treatment plan.

Hereditary Benign Intraepithelial Dyskeratosis: Report of a Case and Re-examination of the Evidence for Locus Heterogeneity

BACKGROUND

Hereditary benign intraepithelial dyskeratosis (HBID) is a rare autosomal-dominant disorder of the conjunctiva and oral mucosa first described in and predominantly affecting descendents of Haliwa-Saponi Native Americans. We report a spontaneous case of histopathologically-confirmed HBID affecting an individual not of Native American ancestry.

MATERIALS AND METHODS

Report of a case with histopathologic examination of an excised conjunctival specimen as well as molecular and cytogenetic analysis.

RESULTS

A Caucasian boy with a history of oral lesions and conjunctival injection from birth developed bilateral corneal opacities at age 5 and underwent penetrating keratoplasty, with recurrence of the corneal opacification shortly after surgery. Examination of a conjunctival biopsy specimen revealed features consistent with HBID. Copy number variant (CNV) analysis revealed a de novo 4q35 duplication that overlapped the duplication previously associated with HBID, although no genes were identified in the common interval. NLRP1 gene sequencing failed to reveal a presumed pathogenic variant.

CONCLUSIONS

HBID may develop de novo in individuals who are not of Native American ancestry. The absence of coding regions in a duplicated region of 4q35 common to both the individual that we report and previously associated with HBID raises questions regarding the significance of this CNV in the pathogenesis of HBID.

Whole exome sequencing identifies a mutation for a novel form of corneal intraepithelial dyskeratosis

BACKGROUND

Corneal intraepithelial dyskeratosis is an extremely rare condition. The classical form, affecting Native American Haliwa-Saponi tribe members, is called hereditary benign intraepithelial dyskeratosis (HBID). Herein, we present a new form of corneal intraepithelial dyskeratosis for which we identified the causative gene by using deep sequencing technology.

METHODS AND RESULTS

A seven member Caucasian French family with two corneal intraepithelial dyskeratosis affected individuals (6-year-old proband and his mother) was ascertained. The proband presented with bilateral complete corneal opacification and dyskeratosis. Palmoplantar hyperkeratosis and laryngeal dyskeratosis were associated with the phenotype. Histopathology studies of cornea and vocal cord biopsies showed dyskeratotic keratinisation. Quantitative PCR ruled out 4q35 duplication, classically described in HBID cases. Next generation sequencing with mean coverage of 50× using the Illumina Hi Seq and whole exome capture processing was performed. Sequence reads were aligned, and screened for single nucleotide variants and insertion/deletion calls. In-house pipeline filtering analyses and comparisons with available databases were performed. A novel missense mutation M77T was discovered for the gene NLRP1 which maps to chromosome 17p13.2. This was a de novo mutation in the proband's mother, following segregation in the family, and not found in 738 control DNA samples. NLRP1 expression was determined in adult corneal epithelium. The amino acid change was found to destabilise significantly the protein structure.

CONCLUSIONS

We describe a new corneal intraepithelial dyskeratosis and how we identified its causative gene. The NLRP1 gene product is implicated in inflammation, autoimmune disorders, and caspase mediated apoptosis. NLRP1 polymorphisms are associated with various diseases.