Novel KIND1 Gene Mutation in Kindler Syndrome With Severe Gastrointestinal Tract Involvement FREE

Kindler syndrome (online Mendelian Inheritance in Man No. 173650) is an autosomal recessive genodermatosis first described by Kindler¹ in the 1950s. It is characterized in infancy by acral trauma-induced blistering and photosensitivity that improves with age. Later in life, progressive poikiloderma with diffuse cutaneous atrophy, telangiectases, and reticulate pigmentation develops. Other features may include nail dystrophy, webbing of the fingers and toes, ectropion formation of the eyelids, chronic inflammation of the oral mucosa, poor dentition with early-onset periodontal disease, and esophageal, anal, vaginal, or urethral stenosis.^2- 9

Siegel and colleagues⁸ demonstrated recently that the molecular basis of this distinct disease is loss of function mutations in the KIND1 gene at chromosome 20p12.3, encoding for the 677–amino acid protein kindlin-1, with a calculated molecular weight of 77.3 kDa. Until now, 18 different mutations were described, and consanguinity of parents was found in about 44% of cases.^2,10- 11 The kindlin-1 protein consists of 4 functional domains with homologies to other polypeptides. The N-terminal domain with homology to filopodin and the C-terminal domain with homology to talin are considered components in the linkage of the actin cytoskeleton to the extracellular matrix in focal adhesion plaques. A bipartite domain with homology to the band 4.1/ezrin/radixin/moesin (FERM) protein family is thought to be involved in the cytoskeleton attachment to the plasma membrane, and the pleckstrin domain in between is a feature of cytoskeletal-associated and/or cell-signaling molecules.^3,12 Therefore, the kindlin-1 protein is strongly suggested to have structural functions, but also functions in directing cell migration, normal cell growth, and cell differentiation and in signal transduction.^3,13- 14 Also, the increased apoptosis and photosensitivity (UV light induces keratinocyte apoptosis in vivo¹⁵) that we¹⁶ and others⁴ have found in Kindler syndrome can be caused by impairment of the signaling functions of integrins owing to mutations in KIND1.

The highest expression of the KIND1 gene can be found in keratinocytes and in the colon, kidney, and placenta, with lower levels in the heart, skeletal muscle, liver, and small intestine. In normal skin, kindlin-1 is present exclusively within the epidermis, particularly in basal keratinocytes.⁸

Diagnosis of Kindler syndrome can be established by the clinical features, course of the disease, and typical findings in immunofluorescence antigen mapping studies and transmission electron microscopy (TEM).¹⁷ Antigen mapping studies do not show any reduction or major alteration in staining of structural proteins of the basement membrane (BM). However, typically, there is a broad, reticular staining pattern at the dermoepidermal junction with antibodies directed against laminin-5 and collagen types IV and VII. Staining with antibodies against integrins and bullous pemphigoid antigen-2 (BPAG2 [collagen type XVII]) shows a linear pattern interrupted in a regular fashion.⁴ In addition, antikeratin-5–positive corpuscles, corresponding to anti-IgM–positive keratin bodies, can be found that are generated by apoptotic keratinocyte cell death.¹⁶

Transmission electron microscopy of some cases shows excessive reduplications of otherwise normal-appearing lamina densa with branching and folding that can be traced deep below the BM zone.^4,16,18 Other cases may show additional interrupted portions of BM lamina densa (which in our case have been observed to be as long as 3-4 basal keratinocytes), sublaminar clefting, and the an increased amount of fibroblastlike cells beneath the BM zone, the cellular projections of which sometimes can be found within the dilated clefts of neighboring basal keratinocytes.¹⁷ In addition, multiple planes of cleavage within the basal keratinocytes and/or in the lamina lucida can be found, but the hemidesmosomes and anchoring fibrils appear normal.⁴

A female neonate, the offspring of consanguineous Turkish parents, developed recurrent blisters on the skin after a normal full-length intrauterine period and an uncomplicated birth (Figure 1). Clinical examination revealed multiple erosions and blisters secondary to minimal trauma on the extremities and the trunk, ie, on the hand below the plastic identification band, on the heels, and below the waist at the lower back. The blisters ruptured easily and healed slowly. The oral and genital mucosas were inconspicuous. In the first postnatal week, failure to nurse well and bloody colic stools occurred, which led to a significant reduction in the infant's weight. Results of laboratory tests such as a compete blood cell count, peripheral eosinophil count, erythrocyte sedimentation rate, measurement of C-reactive protein, serum albumin, and total serum IgE levels, and kidney and liver function tests were within reference ranges. Antineutrophil cytoplasmic antibody levels were not elevated. Further clinical, serological, and microbiological examinations could not detect any infectious cause, and hemorrhagic diarrhea showed no improvement after using a formula preparation that was free of cow-milk protein. The infant was then transferred to our department for further diagnostic examination. Both parents were clinically unaffected; however, the father reported that he also experienced a period of mild blister formation in childhood that improved with age.

Skin biopsy specimens for TEM and antigen mapping studies were obtained 10 days after birth from clinically normal (inner upper arm) and perilesional (periumbilical) skin.

For diagnostic antigen mapping studies, we used monoclonal antibodies against keratins (keratin 1, 5, 8, 10, and 14), plectin 5B3, bullous pemphigoid antigen-1 and -2, integrins α6 and β4, laminin-5, and collagen types IV and VII.

Skin specimens for TEM were analyzed by standard procedures. Briefly, small slices were fixed in phosphate-buffered formaldehyde-glutaraldehyde solution, followed by osmication, dehydration in ascending ethanols, and processing into epoxy resin (Glycidether 100, with hardeners DDSA, MNA, and DMP-30; Serva, Heidelberg, Germany). Semithin (1-μm) and ultrathin (approximately 70- to 80-nm) sections were cut using a diamond knife (Diatome Ltd, Biel, Switzerland). Ultrathin sections were stained by a standardized method using tannic acid, uranyl acetate, and lead citrate. Observations and micrographic documentation were performed on an electron microscope at 80 kV (Zeiss EM 109; Carl Zeiss, Oberkochen, Germany), using a 35-mm camera and negative film (Technical Pan Film 2415; Eastman Kodak Company, Rochester, NY). After development, the film was scanned and processed further electronically.

Gastroduodenoscopy and colonoscopy were performed with an ultrathin fiberglass endoscope during uncomplicated general anesthesia. For histological evaluation, biopsy specimens were taken from the stomach, duodenum, and different parts of the colon and were stained with hematoxylin-eosin by standard procedures.

We extracted genomic DNA from the patient and both parents from peripheral blood samples by standard procedures (Puregene blood kit; Gentra Systems, Minneapolis, Minn). The KIND1 gene was scanned by polymerase chain reaction (PCR) amplification of individual exons and flanking intronic sequences using specific primers and 100 ng of genomic DNA as a template.¹² The PCR reactions were performed in a final volume of 50 μL containing 2.5mM magnesium chloride, 10 pmol of each primer, 4% dimethyl sulfoxide, 125μM deoxyribonucleotide triphosphate, and 2.5 U of Biotherm DNA polymerase (GeneCraft, Muenster, Germany). Cycling conditions were 5 minutes at 94°C, followed by 15 cycles of touchdown PCR starting at 68°C with a temperature decrement of 0.5°C for each cycle, then 40 cycles each for 30 seconds at 94°C, 30 seconds at 61°C, and 30 seconds at 72°C. The PCR fragments were purified using a commercially available PCR and gel purification kit (GFX; Amersham Biosciences, Little Chalfont, England) and forwarded to be sequenced on a capillary electrophoresis system (CEQ8000; Beckman Coulter Inc, Fullerton, Calif). Sequence reactions were performed using a dye terminator cycle sequencing kit (CEQ2000; Beckman Coulter Inc) according to the manufacturer's instructions. For skin biopsy, gastroduodenal endoscopy, and mutation analysis, written informed consent was obtained from both parents.

All structural proteins of the BM zone were detectable with normal intensity. Antigen mapping analysis revealed a focal, extremely broadened, reticular staining pattern for laminin-5 and collagen types IV and VII as the typical diagnostic criterion for Kindler syndrome (Figure 2). Staining with antibodies against integrins and bullous pemphigoid antigen-2 showed a linear pattern interrupted in a regular fashion.

Results of TEM (Figure 3) revealed locally extensive, delocalized remnants of the lamina densa that could be traced as deep as 130 μm below the BM zone. There were also areas where the BM was totally absent or interrupted to 15 to 30 μm of length (1-2 basal keratinocytes). Focally, the lamina lucida appeared to be widened; at places, marked clefting between neighboring basal keratinocytes (often filled with projections of fibroblastlike cells) and subbasal dilatation was observed. Some basal keratinocytes showed marked electron-dense clumping of intracellular tonofilaments and some ultrastructural features of apoptosis. Desmosomes and hemidesmosomes seemed to be ultrastructurally normal.

Histological findings of biopsy specimens taken during gastroduodenoscopy showed normal esophageal and duodenal mucosa but discrete regenerative alterations of the gastric prepyloric part.

Colonoscopy showed ulcerative colitis with inflammatory longitudinal erosions and ulcers with pseudomembraneous alterations of an overall highly vulnerable mucosa in the descending and sigmoid colon and the rectum. Mucosa of the terminal ileum, cecum, and ascending and transversing colon seemed macroscopically normal. Histological examination of biopsy specimens with intact epithelial layer showed a reduction of goblet cells, an increase of mitotic activity, and an accumulation of plasma cells and eosinophils in the lamina propria. Other biopsy specimens were dominated by unspecific ulcerative lesions with lots of fibrin, detritus, and neutrophils associated with granulation tissue. None of the biopsy specimens showed histological criteria of eosinophilic colitis or other specific pathological pictures such as inclusion bodies, bacteria, parasites, crypt abscesses, granulomata, or absence of ganglia.

Mutation analysis of the 15 exons and the exon-intron boundaries of the KIND1 gene of the infant revealed the new mutation consisting of a homozygous deletion of TT in codon 7 of exon 2, localized as 20/21delTT (Figure 4). Consequently, the deletion results in a codon frameshift of +2 and a preterminal stop codon of 6 + 11 amino acids downstream of 11 amino acids, creating a nonfunctional minipeptide of 17 amino acids if translated at all. Mutation analysis of the KIND1 gene of the parents uncovered heterozygous status for this deletion at exon 2. No additional mutation could be detected in the father's gene.

Sequencing of genomic DNA of affected individuals could identify all 9 single nucleotide polymorphisms, consisting of 1-29T/G, 114T/C, 151 + 20C/T, 152-4G/A, 479T/C, 532 + 8T/C, 532 + 34C/T, 533-17A/C, and 722T/C, using the standard numbering system.¹⁹ Intragenic haplotype analysis of these polymorphisms of the affected family revealed a different genetic background from the published Pakistani, white United Kingdom, Omani, and Italian haplotypes and proposed a new Turkish haplotype (Table) associated with the 20/21delTT pathogenic mutation underlying Kindler syndrome.

Gastrointestinal tract involvement in patients with Kindler syndrome is possible but seems to be rare in the literature. To our knowledge, besides esophageal and anal stenosis, no cases with severe gastrointestinal tract involvement have been described. Undoubtedly, the limited accessibility of gastrointestinal tract epithelia and the very low number of patients are reasons for that. In addition, defects that might arise from mutations in structural and functional proteins of the BM zone expressed in internal tissues might not be immediately apparent and may only be detected clinically after further complications have arisen.²⁰ Besides physical trauma from the movement of gut contents, gastrointestinal tract mucosa is also likely to be subjected to osmotic stress, which causes rapid cell shape changes and reversals. Therefore, mutations in the KIND1 gene in combination with secondary factors (eg, mechanical and osmotic stress or bacteria) will cause disruption in epithelium that is only 1 cell layer thick and in the barrier function of the tissue.²⁰ However, owing to high turnover of this epithelium, small localized wounds in the gastrointestinal tract epithelium would heal rapidly and asymptomatically in the absence of any other confounding factors. In this regard, alterations of the prepyloric mucosa with the histological signs of regeneration that we found in our patient also represent signs of mucosal healing of physically and chemically strained pyloric and prepyloric gastric mucosa.

Theoretically, the bloody diarrhea that occurred in our newborn patient could also be caused by other more common diseases such as intolerance to foods in the diet, allergies to proteins, eosinophilic colitis, infections, or inflammatory bowel disease.²¹ Most of these causes could be excluded in our patient by the clinical course (nonresponse to dietary changes), results of laboratory tests and repeated examinations of stool samples (virology, bacterial cultures, and search for ova, cysts, and parasites), and lack of specific macroscopic and histological findings on endoscopy of the gastrointestinal tract. In addition, the simultaneous occurrence of alterations in the skin (erosions and blisters) and the colonic mucosa (erosions and ulcers) highly suggests the same underlying pathogenetic mechanism.

The reason for such severe involvement of colonic mucosa in our patient is unclear. Whether this Turkish haplotype is responsible for this severe gastrointestinal tract involvement is likewise not clear and can only be established by additional reported cases and mutational analysis. Following reports of patients with hereditary epidermolysis bullosa presenting with several of the clinical features of Kindler syndrome, lower gastrointestinal tract complaints are common, especially chronic constipation and perianal blistering.²² Similar to hereditary epidermolysis bullosa, gastrointestinal tract disease in Kindler syndrome tends to occur more severely during childhood and young adulthood.²³ These observations suggest that, in Kindler syndrome, the specialized gastrointestinal tract mucosa can be impaired by increased functional demands and first-time contact with the environment occurring perinatally and during early childhood.

Our patient is the second with Kindler syndrome observed in our department. The other patient, a 49-year-old man, also showed typical clinical signs and course of Kindler syndrome and characteristic alterations in the antigen mapping and TEM findings.¹⁶ Because of stenosis of the small bowel, which was first thought to be caused by Crohn disease, he underwent partial resection of the small bowel. It remains unclear whether this gastrointestinal tract involvement was caused by Crohn disease or Kindler syndrome, which was diagnosed 4 years after the resection. We believe that this observed stenosis of the small bowel was caused by Kindler syndrome because of the lack of typical complications, recurrences, and extraintestinal manifestations of Crohn disease. Owing to the high expression of kindlin-1 in the colon, it is feasible that the gastrointestinal tract alterations in Kindler syndrome could be observed more frequently than described. Similar to dermatitis herpetiformis or Duhring disease, an autoimmune bullous disease, histological signs of gastrointestinal tract involvement in Kindler syndrome could be a rather frequent but often asymptomatic event.²⁴

Our patient's father reported a history of mild blister formation during childhood that improved with age, but whether it was caused by the heterozygous status of the novel deletion mutation 20/21delTT in exon 2 is unclear. This mutation results in a frameshift and premature termination codon and consequently a short polypeptide (consisting of only 17 amino acids), if translated at all. Alternatively, nonsense-mediated RNA decay may result in complete loss of the respective messenger RNA and therefore in a nontranslatable substrate. Maybe this nearly complete loss of all amino acids (98.9%) and complete loss of function could also induce the reported history of blister formation in the patient's father, although he was heterozygous for this mutation, suggesting autosomal recessive transmission. Because he refused further examination in our clinic, other blistering skin diseases cannot be excluded.

Finally, more studies about the function and binding partners of kindlin-1 and more examinations of gastrointestinal tract mucosa are obviously needed to confirm the suspicion of frequent gastrointestinal tract alterations and genetic heterogeneity and to enlighten the pathophysiological background of clinical signs and symptoms in patients with Kindler syndrome.

Correspondence: Helmut Hintner, MD, Department of Dermatology, Paracelsus Private Medical University of Salzburg, Muellner Hauptstraße 48, 5020 Salzburg, Austria (h.hintner@salk.at).

Financial Disclosure: None reported.

Previous Presentation: This study was presented in part at the 32nd Annual Meeting of the Society for Cutaneous Ultrastructure Research; June 3, 2005; Hamburg, Germany.

Accepted for Publication: June 1, 2006.

Author Contributions: Dr Sadler had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Sadler, Laimer, Lanschuetzer, and Bauer. Acquisition of data: Sadler, Klausegger, Muss, Deinsberger, Pohla-Gubo, Bauer, and Hintner. Analysis and interpretation of data: Klausegger, Pohla-Gubo, Bauer, and Hintner. Drafting of the manuscript: Sadler, Muss, Deinsberger, Pohla-Gubo, Laimer, Lanschuetzer, and Bauer. Critical revision of the manuscript for important intellectual content: Klausegger, Muss, Laimer, Lanschuetzer, Bauer, and Hintner. Administrative, technical, and material support: Sadler, Klausegger, Muss, Pohla-Gubo, Lanschuetzer, and Bauer. Study supervision: Klausegger, Bauer, and Hintner.

Acknowledgment: We thank Gerhard Wiche, PhD, Department of Molecular Cell Biology, Vienna Biocenter, Vienna, Austria, for providing the 5B3 antiplectin antibodies.