Short case report 115
A novel mutation in the ABCA12 gene in a Turkish case of Harlequin ichthyosis Hakan Gürkana, Judith Fischerc, Selma Ulusala, Ülfet Vatanseverb, Britta Hartmannc, Hilmi Tozkıra, Nina Schlipfc and Betül Ayşe Acunaşb Clinical Dysmorphology 2015, 24:115–117 a
Tel: + 90 284 235 76 42/2346; fax: + 90 284 235 3451; e-mail: [email protected]
b
Departments of Medical Genetics, Pediatrics, Faculty of Medicine, Trakya University, Edirne, Turkey and cInstitute of Human Genetics, Freiburg, Germany
Received 2 July 2014 Accepted 25 November 2014
Correspondence to Hakan Gürkan, MD, PhD, Department of Medical Genetics, Faculty of Medicine, Trakya University, Edirne, Turkey
List of key features Harlequin ichthyosis Eclabium Ectropion Deep necrosis of the skin Digital necroses Sepsis
Introduction Harlequin ichthyosis (HI; OMIM242500) is the most severe form of autosomal recessive congenital ichthyosis. Affected neonates characteristically have skin covered by ‘armor-like’ thick white plates of scales separated by deep red fissures (Scott et al., 2013). The massive erythematous plate-like scales and profound thickening of fetal skin are accompanied by contraction abnormalities of the eyes, mouth, ears, and appendages (Kaminski et al., 2006). Neonates with this condition are more prone to infection and defective thermoregulation because of the compromised skin barrier (Scott et al., 2013). The diagnosis of the syndrome is usually clinical because of the characteristic appearance of the patients. Autosomal recessive inheritance of mutations in the ATP-binding cassette, subfamily A, member 12 (ABCA12, OMIM*607800, chromosome 2q35) gene was found to be responsible for the disease. The gene coding for the ABCA12 protein is a member of the ABCA subfamily of ATP-binding cassette transporters, which mediate the transport and extrusion of various lipid compounds across membranes (Lefévre et al., 2003). Loss of ABCA12 function results in important impairments in the skin barrier function. Perinatal death is very common because of sepsis or respiratory failure. There are some reports indicating a 50% survival rate with advanced intensive care (Follmann et al., 2013).
Case report An infant directed to the neonatal intensive care unit immediately after birth because of common skin lesions was examined at the age of 2 days. He was born through a Cesarean section at 36 weeks of gestation as the second
child of a consanguineous couple of Turkish origin. The 22-year-old mother was directed to the hospital due to oligohydramnion. Intrauterine growth retardation was present during pregnancy. The infant was externally male and 2420 g, with a head circumference of 34.5 cm. Apgar scores were 6 and 8 at 1 and 5 min, respectively. The presence of rudimentary ears was accompanied by hypoplasia of the hair. Flexion contractures and hypotrichosis were present, accompanied by a clearly high degree of extreme eversion of the lips and ectropion (Fig. 1). Common and deep necrosis of the skin, with deep red fissures dividing the thick white scales throughout the entire body, was obvious. Digital necroses of the hands and feet were observed. On the basis of the typical facial appearance and the deep erythematous fissures of the skin, the case was diagnosed as HI. The patient died on the 17th day of life from sepsis.
Materials and methods Heparinized and EDTA-treated blood samples of the patient and family members were collected. After DNA extraction, mutation analysis of the ABCA12 gene (reference sequence NM_173076) was carried out by next-generation amplicon-sequencing using the MiSeq system (Illumina, San Diego, California, USA). The entire coding region and the exon/intron boundaries of the ABCA12 gene (transcript NM_173076) were sequenced. Sanger sequencing was performed to confirm mutations in the DNA from the patient and the family members. The amplicon panel primers and conditions used were established in our laboratory. Cytogenetic analysis of the patient and parents was also carried out.
Results A homozygous nonsense mutation (c.4950C > A; p. Tyr1650*) in exon 32 of the ABCA12 gene (NM_173076.2) was found in the patient’s DNA sample. The mother and father were found to be heterozygous carriers of the c.4950C > A mutation. The 5-year-old healthy sister was found to carry two wild-type alleles of the ABCA12 gene. The mutation introduces a premature
0962-8827 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
DOI: 10.1097/MCD.0000000000000071
116 Clinical Dysmorphology
2015, Vol 24 No 3
Fig. 1
The patient had ectropion and extreme eversion of the lips, with a white to yellowish armor-like scale over the whole body.
stop codon at position 1650, resulting in a truncated protein, or even no protein, due to nonsense-mediated decay. This mutation has not been previously reported in patients with HI (Fig. 2).
to the plasma membrane to secrete their lipid contents into the extracellular space (Nishifuji and Yoon, 2013). Proper extracellular lipid layer formation is essential for the barrier function of the stratum corneum (Akiyama, 2014).
A cytogenetic analysis of GTL-banded chromosomes from cultured peripheral blood cells of the patient revealed 46,XY,t(1;7)(p33;q35), but both parents had a normal karyotype.
The ABCA12 protein, encoded by the ABCA12 gene, is a keratinocyte lipid transporter protein located in the lamellar granules of the granular layer of keratinocytes and transports lipid glucosylceramides to the extracellular space through lamellar granules (Scott et al., 2013). Mutations in the ABCA12 gene have been reported to be the cause of autosomal recessive ichthyosis syndromes, including HI, congenital ichthyosiform erythroderma, and lamellar ichthyosis (Akiyama, 2010). HI is the most severe form of these congenital ichthyosis syndromes. It has been suggested that lamellar granules are absent or reduced in number in the skin of HI patients (Rajpopat
Discussion Keratinocytes develop into corneocytes through the breakdown of their nuclei and organelles and compose the stratum corneum, which is essential for the barrier function of the skin (Hernández-Martín et al., 2013). Lamellar granules, originating from a part of the Golgi apparatus, contain lipid precursors, and during cornification, they fuse Fig. 2
(a)
(b)
(c)
Partial electropherograms of ABCA12 exon 32 of (a) the mother, (b) the father, and (c) the index case. Arrows in (a) and (b) indicate a heterozygous c.4950C > A mutation of the ABCA12 gene in both parents, whereas the arrow in (c) indicates the mutation in the index case is homozygous.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
A novel mutation in ABCA12 in a Turkish case of HI Gürkan et al. 117
et al., 2011). Newborns often die within the first weeks of life because of a compromised skin barrier, resulting in infections, dysregulation of thermogenesis, and excess water loss.
Acknowledgements
To date, a number of ABCA12 mutations have been reported for cases of HI. Usually, the patients carry at least one nonsense, frameshift, or splice mutation that results in a truncated, nonfunctional protein (Akiyama, 2010). Although these mutations are generally nonsense, in a study by Umemoto et al. (2011), missense mutations in ABCA12 located in highly conserved regions of the gene were reported to be the cause of HI (Ahmed and O’Toole, 2014). An interesting case has been reported by Castiglia et al. (2009), in which the HI phenotype is due to uniparental disomy of chromosome 2 carrying a nonsense mutation in the ABCA12 gene.
Conflicts of interest
The patient in the present report was tentatively diagnosed with HI immediately after birth and was shown to carry a homozygous nonsense mutation, c.4950C > A, in the ABCA12 gene. The early death of the proband may be related to the homozygous nature of the mutation (Rajpopat et al., 2011). Although there was no family history of HI, the parents of the proband in this report were consanguineous. A tentative prenatal diagnosis of HI is very rare, with only eight cases reported to date (Follmann et al., 2013). In situations in which only one parent is a carrier of an ABCA12-truncating mutation, the possibility of HI in the fetus due to uniparental disomy should be kept in mind. Because of the severity of the syndrome, the family received genetic consultation about prenatal diagnosis for possible future pregnancies. Moreover, this is the first reported case in which the HI patient is a de-novo (1;7)(p33;q35) translocation carrier.
The author thanks Frau Christine Hodler for excellent technical help.
There are no conflicts of interest.
References Ahmed H, O’Toole EA (2014). Recent advances in the genetics and management of harlequin ichthyosis. Pediatr Dermatol 31:539–546. Akiyama M (2010). ABCA12 mutations and autosomal recessive congenital ichthyosis: a review of genotype/phenotype correlations and of pathogenetic concepts. Hum Mutat 31:1090–1096. Akiyama M (2014). The roles of ABCA12 in epidermal lipid barrier formation and keratinocyte differentiation. Biochim Biophys Acta 1841:435–440. Castiglia D, Castori M, Pisaneschi E, Sommi M, Covaciu C, Zambruno G, et al. (2009). Trisomic rescue causing reduction to homozygosity for a novel ABCA12 mutation in harlequin ichthyosis. Clin Genet 76:392–397. Follmann J, Macchiella D, Whybra C, Mildenberger E, Poarangan C, Zechner U, Bartsch O (2013). Identification of novel mutations in the ABCA12 gene, c.1857delA and c.5653-5655delTAT, causing harlequin ichthyosis. Gene 531:510–513. Hernández-Martín A, Torrelo-Fernández A, de Lucas-Laguna R, Casco F, González-Sarmiento R, Vega A, et al. (2013). First symposium of ichthyosis experts. Actas Dermosifiliogr 104:877–882. Kaminski WE, Piehler A, Wenzel JJ (2006). ABC A-subfamily transporters: structure, function and disease. Biochim Biophys Acta 1762:510–524. Lefévre C, Audebert S, Jobard F, Bouadjar B, Lakhdar H, BoughdeneStambouli O, et al. (2003). Mutations in the transporter ABCA12 are associated with lamellar ichthyosis type 2. Hum Mol Genet 12:2369–2378. Nishifuji K, Yoon JS (2013). The stratum corneum: the rampart of the mammalian body. Vet Dermatol 24:60–72, e15-6. Rajpopat S, Moss C, Mellerio J, Vahlquist A, Gånemo A, Hellstrom-Pigg M, et al. (2011). Harlequin ichthyosis: a review of clinical and molecular findings in 45 cases. Arch Dermatol 147:681–686. Scott CA, Rajpopat S, Di WL (2013). Harlequin ichthyosis: ABCA12 mutations underlie defective lipid transport, reduced protease regulation and skin-barrier dysfunction. Cell Tissue Res 351:281–288. Umemoto H, Akiyama M, Yanagi T, Sakai K, Aoyama Y, Oizumi A, et al. (2011). New insight into genotype/phenotype correlations in ABCA12 mutations in harlequin ichthyosis. J Dermatol Sci 61:136–139.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
A novel mutation in the ABCA12 gene in a Turkish case of Harlequin ichthyosis Hakan Gürkana, Judith Fischerc, Selma Ulusala, Ülfet Vatanseverb, Britta Hartmannc, Hilmi Tozkıra, Nina Schlipfc and Betül Ayşe Acunaşb Clinical Dysmorphology 2015, 24:115–117 a
Tel: + 90 284 235 76 42/2346; fax: + 90 284 235 3451; e-mail: [email protected]
b
Departments of Medical Genetics, Pediatrics, Faculty of Medicine, Trakya University, Edirne, Turkey and cInstitute of Human Genetics, Freiburg, Germany
Received 2 July 2014 Accepted 25 November 2014
Correspondence to Hakan Gürkan, MD, PhD, Department of Medical Genetics, Faculty of Medicine, Trakya University, Edirne, Turkey
List of key features Harlequin ichthyosis Eclabium Ectropion Deep necrosis of the skin Digital necroses Sepsis
Introduction Harlequin ichthyosis (HI; OMIM242500) is the most severe form of autosomal recessive congenital ichthyosis. Affected neonates characteristically have skin covered by ‘armor-like’ thick white plates of scales separated by deep red fissures (Scott et al., 2013). The massive erythematous plate-like scales and profound thickening of fetal skin are accompanied by contraction abnormalities of the eyes, mouth, ears, and appendages (Kaminski et al., 2006). Neonates with this condition are more prone to infection and defective thermoregulation because of the compromised skin barrier (Scott et al., 2013). The diagnosis of the syndrome is usually clinical because of the characteristic appearance of the patients. Autosomal recessive inheritance of mutations in the ATP-binding cassette, subfamily A, member 12 (ABCA12, OMIM*607800, chromosome 2q35) gene was found to be responsible for the disease. The gene coding for the ABCA12 protein is a member of the ABCA subfamily of ATP-binding cassette transporters, which mediate the transport and extrusion of various lipid compounds across membranes (Lefévre et al., 2003). Loss of ABCA12 function results in important impairments in the skin barrier function. Perinatal death is very common because of sepsis or respiratory failure. There are some reports indicating a 50% survival rate with advanced intensive care (Follmann et al., 2013).
Case report An infant directed to the neonatal intensive care unit immediately after birth because of common skin lesions was examined at the age of 2 days. He was born through a Cesarean section at 36 weeks of gestation as the second
child of a consanguineous couple of Turkish origin. The 22-year-old mother was directed to the hospital due to oligohydramnion. Intrauterine growth retardation was present during pregnancy. The infant was externally male and 2420 g, with a head circumference of 34.5 cm. Apgar scores were 6 and 8 at 1 and 5 min, respectively. The presence of rudimentary ears was accompanied by hypoplasia of the hair. Flexion contractures and hypotrichosis were present, accompanied by a clearly high degree of extreme eversion of the lips and ectropion (Fig. 1). Common and deep necrosis of the skin, with deep red fissures dividing the thick white scales throughout the entire body, was obvious. Digital necroses of the hands and feet were observed. On the basis of the typical facial appearance and the deep erythematous fissures of the skin, the case was diagnosed as HI. The patient died on the 17th day of life from sepsis.
Materials and methods Heparinized and EDTA-treated blood samples of the patient and family members were collected. After DNA extraction, mutation analysis of the ABCA12 gene (reference sequence NM_173076) was carried out by next-generation amplicon-sequencing using the MiSeq system (Illumina, San Diego, California, USA). The entire coding region and the exon/intron boundaries of the ABCA12 gene (transcript NM_173076) were sequenced. Sanger sequencing was performed to confirm mutations in the DNA from the patient and the family members. The amplicon panel primers and conditions used were established in our laboratory. Cytogenetic analysis of the patient and parents was also carried out.
Results A homozygous nonsense mutation (c.4950C > A; p. Tyr1650*) in exon 32 of the ABCA12 gene (NM_173076.2) was found in the patient’s DNA sample. The mother and father were found to be heterozygous carriers of the c.4950C > A mutation. The 5-year-old healthy sister was found to carry two wild-type alleles of the ABCA12 gene. The mutation introduces a premature
0962-8827 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
DOI: 10.1097/MCD.0000000000000071
116 Clinical Dysmorphology
2015, Vol 24 No 3
Fig. 1
The patient had ectropion and extreme eversion of the lips, with a white to yellowish armor-like scale over the whole body.
stop codon at position 1650, resulting in a truncated protein, or even no protein, due to nonsense-mediated decay. This mutation has not been previously reported in patients with HI (Fig. 2).
to the plasma membrane to secrete their lipid contents into the extracellular space (Nishifuji and Yoon, 2013). Proper extracellular lipid layer formation is essential for the barrier function of the stratum corneum (Akiyama, 2014).
A cytogenetic analysis of GTL-banded chromosomes from cultured peripheral blood cells of the patient revealed 46,XY,t(1;7)(p33;q35), but both parents had a normal karyotype.
The ABCA12 protein, encoded by the ABCA12 gene, is a keratinocyte lipid transporter protein located in the lamellar granules of the granular layer of keratinocytes and transports lipid glucosylceramides to the extracellular space through lamellar granules (Scott et al., 2013). Mutations in the ABCA12 gene have been reported to be the cause of autosomal recessive ichthyosis syndromes, including HI, congenital ichthyosiform erythroderma, and lamellar ichthyosis (Akiyama, 2010). HI is the most severe form of these congenital ichthyosis syndromes. It has been suggested that lamellar granules are absent or reduced in number in the skin of HI patients (Rajpopat
Discussion Keratinocytes develop into corneocytes through the breakdown of their nuclei and organelles and compose the stratum corneum, which is essential for the barrier function of the skin (Hernández-Martín et al., 2013). Lamellar granules, originating from a part of the Golgi apparatus, contain lipid precursors, and during cornification, they fuse Fig. 2
(a)
(b)
(c)
Partial electropherograms of ABCA12 exon 32 of (a) the mother, (b) the father, and (c) the index case. Arrows in (a) and (b) indicate a heterozygous c.4950C > A mutation of the ABCA12 gene in both parents, whereas the arrow in (c) indicates the mutation in the index case is homozygous.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
A novel mutation in ABCA12 in a Turkish case of HI Gürkan et al. 117
et al., 2011). Newborns often die within the first weeks of life because of a compromised skin barrier, resulting in infections, dysregulation of thermogenesis, and excess water loss.
Acknowledgements
To date, a number of ABCA12 mutations have been reported for cases of HI. Usually, the patients carry at least one nonsense, frameshift, or splice mutation that results in a truncated, nonfunctional protein (Akiyama, 2010). Although these mutations are generally nonsense, in a study by Umemoto et al. (2011), missense mutations in ABCA12 located in highly conserved regions of the gene were reported to be the cause of HI (Ahmed and O’Toole, 2014). An interesting case has been reported by Castiglia et al. (2009), in which the HI phenotype is due to uniparental disomy of chromosome 2 carrying a nonsense mutation in the ABCA12 gene.
Conflicts of interest
The patient in the present report was tentatively diagnosed with HI immediately after birth and was shown to carry a homozygous nonsense mutation, c.4950C > A, in the ABCA12 gene. The early death of the proband may be related to the homozygous nature of the mutation (Rajpopat et al., 2011). Although there was no family history of HI, the parents of the proband in this report were consanguineous. A tentative prenatal diagnosis of HI is very rare, with only eight cases reported to date (Follmann et al., 2013). In situations in which only one parent is a carrier of an ABCA12-truncating mutation, the possibility of HI in the fetus due to uniparental disomy should be kept in mind. Because of the severity of the syndrome, the family received genetic consultation about prenatal diagnosis for possible future pregnancies. Moreover, this is the first reported case in which the HI patient is a de-novo (1;7)(p33;q35) translocation carrier.
The author thanks Frau Christine Hodler for excellent technical help.
There are no conflicts of interest.
References Ahmed H, O’Toole EA (2014). Recent advances in the genetics and management of harlequin ichthyosis. Pediatr Dermatol 31:539–546. Akiyama M (2010). ABCA12 mutations and autosomal recessive congenital ichthyosis: a review of genotype/phenotype correlations and of pathogenetic concepts. Hum Mutat 31:1090–1096. Akiyama M (2014). The roles of ABCA12 in epidermal lipid barrier formation and keratinocyte differentiation. Biochim Biophys Acta 1841:435–440. Castiglia D, Castori M, Pisaneschi E, Sommi M, Covaciu C, Zambruno G, et al. (2009). Trisomic rescue causing reduction to homozygosity for a novel ABCA12 mutation in harlequin ichthyosis. Clin Genet 76:392–397. Follmann J, Macchiella D, Whybra C, Mildenberger E, Poarangan C, Zechner U, Bartsch O (2013). Identification of novel mutations in the ABCA12 gene, c.1857delA and c.5653-5655delTAT, causing harlequin ichthyosis. Gene 531:510–513. Hernández-Martín A, Torrelo-Fernández A, de Lucas-Laguna R, Casco F, González-Sarmiento R, Vega A, et al. (2013). First symposium of ichthyosis experts. Actas Dermosifiliogr 104:877–882. Kaminski WE, Piehler A, Wenzel JJ (2006). ABC A-subfamily transporters: structure, function and disease. Biochim Biophys Acta 1762:510–524. Lefévre C, Audebert S, Jobard F, Bouadjar B, Lakhdar H, BoughdeneStambouli O, et al. (2003). Mutations in the transporter ABCA12 are associated with lamellar ichthyosis type 2. Hum Mol Genet 12:2369–2378. Nishifuji K, Yoon JS (2013). The stratum corneum: the rampart of the mammalian body. Vet Dermatol 24:60–72, e15-6. Rajpopat S, Moss C, Mellerio J, Vahlquist A, Gånemo A, Hellstrom-Pigg M, et al. (2011). Harlequin ichthyosis: a review of clinical and molecular findings in 45 cases. Arch Dermatol 147:681–686. Scott CA, Rajpopat S, Di WL (2013). Harlequin ichthyosis: ABCA12 mutations underlie defective lipid transport, reduced protease regulation and skin-barrier dysfunction. Cell Tissue Res 351:281–288. Umemoto H, Akiyama M, Yanagi T, Sakai K, Aoyama Y, Oizumi A, et al. (2011). New insight into genotype/phenotype correlations in ABCA12 mutations in harlequin ichthyosis. J Dermatol Sci 61:136–139.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
