Ocular findings in ichthyosis follicularis-alopecia-photophobia (IFAP) syndrome

Syndromic or non-syndromic congenital ichthyosis? A case report of two brothers with ichthyosis but microphthalmia and blindness in only one brother

We present the cases of two brothers with ichthyosis, born to consanguineous parents, with the eldest having extracutaneous manifestations in the form of microphthalmia and corneal opacities causing complete blindness. Initially, we were faced with the question of whether the phenotype in this family was due to the effects of a single pleiotropic, presumably autosomal recessive gene manifesting as a syndromic form of ichthyosis, or whether there were multiple causal genes, and the ichthyosis was non-syndromic. Ultimately, clinical follow-up of the family, combined with research-based exome sequencing established a diagnosis of NIPAL4 autosomal recessive congenital ichthyosis in both brothers, but the ocular abnormalities causing blindness in the older brother were due to coexisting autosomal recessively inherited loss of function mutations in peroxidasin, the latter finding also seen in a sister unaffected by ichthyosis.

Ocular findings and genomics of X-linked recessive disorders: A review

Advent of new sequencing technologies and modern diagnostic procedures has opened the door for a deeper understanding of disorders about which little was known previously. Discovery of novel genes, new genetic variants in previously known genes and better techniques of functional validation has immensely contributed to unraveling the molecular basis of genetic disorders. Availability of knockout animal models like the zebrafish and gene editing tools like CRISPR-Cas9 has elucidated the function of many new genes and helped us to better understand the functional consequences of various gene defects. This has also led to better diagnosis and therapeutic interventions. In this context, a good body of research work has been done on X-linked recessive disorders with ocular findings. This review will focus on ocular and genetic findings of these rare disorders. To our knowledge, this is the first comprehensive review encompassing ocular and genomic spectrum of X-linked recessive disorders.

Limbal Stem Cell Dysfunction in Ichthyosis Follicularis, Alopecia, and Photophobia Syndrome

PURPOSE

To describe the presentation and management of limbal stem cell dysfunction in ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome.

METHODS

A retrospective case report.

RESULTS

A 6-day-old male infant was diagnosed with IFAP syndrome based on family history and a mutation detected in the MBTPS2 gene. Initial examination showed hyperkeratotic eyelids, madarosis, and lagophthalmos, but otherwise clear corneas. He developed bilateral central corneal epithelial defects spontaneously 6 months later, which were managed with aggressive lubrication, prophylactic antibiotics, and bilateral permanent lateral tarsorrhaphies at 7 months of age. During the procedure, the patient was noted to have bilateral limbal thickening, peripheral corneal pannus with underlying stromal scarring, and late fluorescein staining of the corneal surface. Anterior segment optical coherence tomography demonstrated a significantly abnormal and hyperreflective epithelial surface overlying a thinned corneal stroma, suggestive of limbal stem cell dysfunction. The corneal surface was maintained with lubrication and tarsorrhaphy and has remained stable since.

CONCLUSIONS

The progressive conjunctivalization, spontaneous epithelial defects, and anterior segment optical coherence tomography features are highly suggestive of limbal stem cell dysfunction in IFAP syndrome. Optimizing the ocular surface is of importance in the management of children with this rare disease.

Ichthyosis follicularis, atrichia and photophobia (IFAP) and hereditary mucoepithelial dysplasia: Two syndromes that share a common clinical spectrum

Ichthyosis follicularis, atrichia and photophobia syndrome (IFAP) is an X-linked inherited disease caused by pathogenic variants in the gene encoding the membrane-bound transcription factor peptidase, site 2 (MBTPS2). Clinical presentation includes ichthyosis follicularis, alopecia, photophobia and developmental delay. Hereditary mucoepithelial dysplasia (HMD) is a dominantly inherited disease characterized by keratitis, non-scarring alopecia, skin lesions including follicular keratosis, perineal erythema, and mucosal involvement. Recently, variants in SREBF1, a gene coding for a transcription factor related to cholesterol and fatty acid synthesis, have been associated with the disease. These two syndromes share a common clinical spectrum. Here, we describe an IFAP syndrome patient with a novel variant in the MBTPS2 gene and an HMD patient with a previously reported variant in the SREBF1 gene. In addition, we present a review of the literature describing the triad characterized by non-scarring alopecia, keratosis follicularis, and ocular symptoms common in both IFAP and HMD patients to raise awareness of these underdiagnosed diseases. We also highlight the subtle differences in clinical presentation between the two disorders to better enable differentiation.

Ichthyosis Follicularis, Alopecia, and Photophobia (IFAP) Syndrome: A Case Report and Review of Cases Reported from India

Ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome is characterized by the triad of follicular keratotic papules, total to subtotal alopecia, and photophobia. We hereby report a case of IFAP syndrome in a 1-year-old boy who presented with all these classical features along with hyperkeratotic plaques over knees, plantar keratoderma, and umbilical hernia. Also, literature review of cases reported from India is being presented.

A novel mutation in MBTPS2 causes ichthyosis follicularis, alopecia, and photophobia syndrome

Background

The ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome is a rare X‐linked genodermatosis characterized by noninflammatory spiny follicular hyperkeratosis, severe photophobia, and non‐scarring alopecia with variable severities. IFAP syndrome results from mutations in the gene encoding the membrane‐bound transcription factor peptidase, site 2 (MBTPS2).

Methods

We present an 11‐year‐old male with typical clinical features of IFAP syndrome, including diffuse follicular hyperkeratosis, alopecia, photophobia, psoriasiform plaques, short statue, nail dystrophy, mental retardation, and seizures.

Results

A novel missense mutation (NM_015884.4: c.1298T > C; NP_056968.1: p. L433P) in the membrane‐bound transcription factor peptidase, site 2 gene (MBTPS2) was identified in our patient. The heterozygous MBTPS2 mutation was identified in his mother but not his father.

Conclusion

This study demonstrated a novel MBTPS2 mutation in a patient with IFAP syndrome and thus expands the known MBPTS2 molecular repertoire.

Ocular manifestations, complications and management of congenital ichthyoses: a new look

Congenital ichthyoses (CI) are rare genetic skin keratinisation diseases characterised by generalised scaling and a variable degree of erythema and hyperkeratosis. Ocular involvement includes the eyelids, conjunctiva and all layers of the cornea. Ophthalmic input should include regular slit lamp review with the primary aim to prevent a corneal epithelial defect, secondary bacterial infection, scarring or perforation. This review highlights the current literature regarding ophthalmic findings and management of CI.

A Case of IFAP Syndrome with Severe Atopic Dermatitis

Introduction. The IFAP syndrome is a rare X-linked genetic disorder characterized by the triad of follicular ichthyosis, atrichia, and photophobia. Case Report. A three-month-old Caucasian, male patient was observed with noncicatricial universal alopecia and persistent eczema from birth. He had dystrophic nails, spiky follicular hyperkeratosis, and photophobia which became apparent at the first year of life. Short stature and psychomotor developmental delay were also noticed. Histopathological examination of skin biopsy on left thigh showed epidermis with irregular acanthosis, lamellar orthokeratotic hyperkeratosis, and hair follicles fulfilled by parakeratotic hyperkeratosis. The chromosomal study showed a karyotype 46, XY. Total IgE was 374 IU/mL. One missense mutation c.1360G>C (p.Ala454Pro) in hemizygosity was detected on the MBTPS2 gene thus confirming the diagnosis of IFAP syndrome. Conclusions. We describe a boy with a typical clinical presentation of IFAP syndrome and severe atopic manifestations. A novel missense mutation c.1360G>C (p.Ala454Pro) in MBTPS2 gene was observed. The phenotypic expression of disease is quantitatively related to a reduced function of a key cellular regulatory system affecting cholesterol and endoplasmic reticulum homeostasis. It can cause epithelial disturbance with failure in differentiation of epidermal structures and abnormal skin permeability barrier. However, no correlation phenotype/genotype could be established.

Photoletter to the editor: A new variant of ichthyosis follicularis with alopecia and photophobia (IFAP) syndrome with coexisting psoriasiform lesions and palmoplantar keratoderma. IFAP-PPK syndrome?

IFAP is an acronym for a rare congenital ectodermal disorder characterized by ichthyosis follicularis, alopecia and photophobia. A recessive X-linked mode of inheritance was initially proposed but recent reports in girls suggested genetic heterogeneity of this syndrome. We herein describe a 1-year-old boy with clinical features typical of IFAP syndrome plus psoriasis-like lesions and palmoplantar keratoderma (PPK).

Ichthyosis follicularis, alopecia, and photophobia syndrome: a case report and a pathological insight into pilosebaceous anomaly

Ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome (OMIM 308205) is an extremely rare X-linked oculocutaneous genetic disorder characterized by follicular keratotic papules, total to subtotal alopecia, and photophobia. Previous reports depicted the histopathological features of affected skin lesions, represented by marked follicular plugging and hypoplastic pilosebaceous structures. However, past studies provided limited pathological information of pilosebaceous unit anomaly. Here, we report a 3-year-old boy's case with this uncommon condition. In this case, scalp biopsy samples were processed by both vertical and transverse sectioning techniques, which enabled a more detailed and quantitative pathological analysis of pilosebaceous structures. In vertical slices, miniaturized anagen hair follicles with characteristic follicular plugs were observed. A transverse section identified abortive sebaceous glands in hair follicles, a finding rarely observed in vertical sections. In addition, a transverse slice demonstrated that the number of total hair follicles was not significantly decreased compared with the average hair follicle density in Asians, suggesting that the pilosebaceous hypoplasia might arise from impaired maturation, not from initiation defect, during hair follicle morphogenesis. This study provides a more comprehensive pathological insight into pilosebaceous anomaly in IFAP syndrome and substantiats the usefulness of the combination of vertical and transverse sectioning approaches in the pathological examination of congenital hypotrichosis, including IFAP syndrome.

Ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome

The IFAP syndrome is a rare X-linked genetic disorder reported in nearly 40 patients. It is characterized by the triad of Ichthyosis Follicularis, Alopecia, and Photophobia from birth. Other features such as short stature, intellectual disability, and seizures may develop in the first few years of life. Skin histopathology is non-specific and consists of dilated hair follicles with keratin plugs extending above the surface of the skin, decreased or absent sebaceous glands, and decreased desmosomes in number and size. The disorder results from mutations in the MBTPS2 gene that impairs cholesterol homeostasis and the ability to cope with endoplasmic reticulum stress. Follicular hyperkeratosis can be treated using topical keratolytics, emollients and urea preparations. A moderate response to acitretin therapy has been noted in some patients. Intensive lubrication of the ocular surface is essential. Life expectancy in patients with IFAP syndrome can vary from death in the neonatal period to normal surviving. Cardiopulmonary complications remain the major cause of death.

X-linked ichthyosis: an oculocutaneous genodermatosis

X-linked ichthyosis (XLI) is an X-linked recessive disorder of cutaneous keratinization with possible extracutaneous manifestations. It was first described as a distinct type of ichthyosis in 1965. XLI is caused by a deficiency in steroid sulfatase activity, which results in abnormal desquamation and a retention hyperkeratosis. XLI is usually evident during the first few weeks of life as polygonal, loosely adherent translucent scales in a generalized distribution that desquamate widely. These are quickly replaced by large, dark brown, tightly adherent scales occurring primarily symmetrically on the extensor surfaces and the side of the trunk. In addition, extracutaneous manifestations such as corneal opacities, cryptorchidism, and abnormalities related to contiguous gene syndromes may be observed. Diagnosis of XLI is usually made clinically, as the histopathology is nonspecific, but confirmation may be obtained through either biochemical or genetic analysis. Treatment should focus on cutaneous hydration, lubrication, and keratolysis and includes topical moisturizers and topical retinoids.

Ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome due to mutation of the gene MBTPS2 in a large Australian kindred

Ichthyosis follicularis, alopecia and photophobia (IFAP) is a rare genodermatosis. Most patients have been men without significant family history. We present the largest kindred of IFAP reported to date in the medical literature clearly demonstrating X-linked inheritance. The gene defect has recently been mapped to Xp22.11-p22.13. Missense mutations of the gene, MBTPS2, which codes for an intramembrane zinc metalloprotease essential for cholesterol homeostasis and endoplasmic reticulum stress response, are associated with the IFAP phenotype in this kindred. We describe the clinical features and discuss the differential diagnosis of IFAP. Our proband has benefited from treatment with acitretin.

IFAP syndrome is caused by deficiency in MBTPS2, an intramembrane zinc metalloprotease essential for cholesterol homeostasis and ER stress response

Ichthyosis follicularis with atrichia and photophobia (IFAP syndrome) is a rare X-linked, oculocutaneous human disorder. Here, we assign the IFAP locus to the 5.4 Mb region between DXS989 and DXS8019 on Xp22.11-p22.13 and provide evidence that missense mutations exchanging highly conserved amino acids of membrane-bound transcription factor protease, site 2 (MBTPS2) are associated with this phenotype. MBTPS2, a membrane-embedded zinc metalloprotease, activates signaling proteins involved in sterol control of transcription and ER stress response. Wild-type MBTPS2 was able to complement the protease deficiency in Chinese hamster M19 cells as shown by induction of an SRE-regulated reporter gene in transient transfection experiments and by growth of stably transfected cells in media devoid of cholesterol and lipids. These functions were impaired in five mutations as detected in unrelated patients. The degree of diminished activity correlated with clinical severity as noted in male patients. Our findings indicate that the phenotypic expression of IFAP syndrome is quantitatively related to a reduced function of a key cellular regulatory system affecting cholesterol homeostasis and ability to cope with ER stress.