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Papillon–Lefèvre Syndrome: Mutations and Polymorphisms in the Cathepsin C Gene

2001; Elsevier BV; Volume: 116; Issue: 2 Linguagem: Inglês

10.1046/j.1523-1747.2001.01244.x

1523-1747

Aoi Nakano, Hajime Nakano, Sal LaForgia, Leena Pulkkinen, Jouni Uitto, Kazuo Nomura, Yoshio ONO, Isao Hashimoto,

Streptococcal Infections and Treatments

The Papillon–Lefèvre syndrome, inherited in an autosomal recessive pattern, manifests with palmoplantar keratoderma and early, destructive periodontitis. Recently, mutations in the gene encoding cathepsin C have been disclosed in a limited number of families with Papillon–Lefèvre syndrome. We have examined two multiplex families with Papillon–Lefèvre syndrome, and evaluated the gene encoding cathepsin C for mutations. The mutation detection strategy consisted of polymerase chain reaction amplification of all seven exons and flanking intronic sequences, followed by direct nucleotide sequencing. This strategy identified two missense mutations, W39S and G301S, affecting highly conserved amino acid residues within the cathepsin C polypeptide. The affected individuals were homozygotes whereas heterozygous carriers of the mutations were clinically unaffected, confirming the recessive nature of the mutations. Addition of these cathepsin C gene mutations into the expanding Papillon–Lefèvre syndrome mutation database allows further development of genotype/phenotype correlations towards understanding this severe genodermatosis. The Papillon–Lefèvre syndrome, inherited in an autosomal recessive pattern, manifests with palmoplantar keratoderma and early, destructive periodontitis. Recently, mutations in the gene encoding cathepsin C have been disclosed in a limited number of families with Papillon–Lefèvre syndrome. We have examined two multiplex families with Papillon–Lefèvre syndrome, and evaluated the gene encoding cathepsin C for mutations. The mutation detection strategy consisted of polymerase chain reaction amplification of all seven exons and flanking intronic sequences, followed by direct nucleotide sequencing. This strategy identified two missense mutations, W39S and G301S, affecting highly conserved amino acid residues within the cathepsin C polypeptide. The affected individuals were homozygotes whereas heterozygous carriers of the mutations were clinically unaffected, confirming the recessive nature of the mutations. Addition of these cathepsin C gene mutations into the expanding Papillon–Lefèvre syndrome mutation database allows further development of genotype/phenotype correlations towards understanding this severe genodermatosis. Papillon–Lefèvre syndrome cathepsin C gene The Papillon–Lefèvre syndrome (PLS; OMIM no. 245000) is a relatively rare autosomal recessive condition manifesting with palmoplantar keratoderma, combined with a rapidly progressive periodontitis (Papillon and Lefèvre, 1924Papillon M.M. Lefèvre P. Deux cas de keratodermie palmaire et plantaire symmetrique familiale (maladie de Meleda) chez le frere et la soeur: coexistense dans les duex cas d'alterations dentaires gravis.Bull Soc Fr Dermatol Syphilis. 1924; 31: 81-87Google Scholar; for reviews seeHaneke, 1979Haneke E. The Papillon–Lefèvre syndrome: keratosis palmoplantaris with periodontopathy.Hum Genet. 1979; 51: 1-35Crossref PubMed Scopus (171) Google Scholar;Hart and Shapira, 1994Hart T.C. Shapira L. Papillon–Lefèvre syndrome.Periodontology. 1994; 2000: 88-100Crossref Scopus (90) Google Scholar;Siragusa et al., 2000Siragusa M. Romano C. Batticane N. Batolo D. Schepis C. A new family with Papillon–Lefèvre syndrome: effectiveness of etretinate treatment.Cutis. 2000; 65: 151-155PubMed Google Scholar). The estimated prevalence is one to four per 106 (Verma et al., 1979Verma K. Chadda M. Joshi R. Papillon–Lefèvre syndrome.Int J Dermatol. 1979; 18: 146-149Crossref PubMed Scopus (13) Google Scholar). The initial clinical signs of skin involvement are usually evident during the first 4 y of life, and a histopathologic examination of the affected skin shows hyperkeratosis with psoriasiform parakeratosis. The gingival involvement may be noticeable as early as 3 or 4 y of age. Both the deciduous teeth and permanent teeth are lost prematurely, and in general the patients affected by PLS are edentulous by the age of 15 y. Calcification of the dura mater has been suggested to be the third component of the syndrome (Gorlin et al., 1964Gorlin R.J. Sedano H. Anderson V.E. The syndrome of palmar-plantar hyperkeratosis and premature periodontal destruction of the teeth: a clinical and genetic analysis of the Papillon–Lefèvre syndrome.J Pediatr. 1964; 65: 895-908Abstract Full Text PDF PubMed Google Scholar). A number of suggestions for pathoetiology in PLS have been advanced over the years, including immune abnormalities and susceptibility to bacterial infections (seeHart and Shapira, 1994Hart T.C. Shapira L. Papillon–Lefèvre syndrome.Periodontology. 1994; 2000: 88-100Crossref Scopus (90) Google Scholar); however, the link between the cutaneous and gingival findings has not been clear. Originally, the PLS locus was placed on human chromosome 11q14 by homozygosity linkage mapping (Fischer and Blanchet-Bardon, 1997Fischer J. Blanchet-Bardon C. Prud'homme J-F, Pavek S, Steijlen PM, Dubertret L, Weissenbach J. Mapping of Papillon–Lefèvre syndrome to the chromosome 11q14 region.Eur J Hum Genet. 1997; 5: 156-160PubMed Google Scholar;Laass et al., 1997Laass M.W. Hennies H.C. Preis S. et al.Localisation of a gene for Papillon–Lefèvre syndrome to chromosome 11q14-q21 by homozygosity mapping.Hum Genet. 1997; 101: 376-382https://doi.org/10.1007/s004390050645Crossref PubMed Scopus (52) Google Scholar;Hart et al., 1998Hart T.C. Bowden D.W. Ghaffar K.A. et al.Sublocalization of the Papillon–Lefèvre syndrome locus on 11q14-q21.Am J Med Genet. 1998; 79: 134-139Crossref PubMed Scopus (45) Google Scholar,Hart et al., 2000cHart T.C. Walker S.J. Bowden D.W. Hart P.S. Callison S.A. Bobby P.L. Firatli E. An integrated physical and genetic map of the PLS locus interval on chromosome 11q14.Mamm Genome. 2000; 11: 243-246Crossref PubMed Scopus (7) Google Scholar), and quite recently a number of mutations in patients with PLS have been reported in the gene encoding human cathepsin C (CTSC) (Toomes et al., 1999Toomes C. James J. Wood A.J. et al.Loss-of-function mutations in the cathepsin C gene result in periodontal disease and palmoplantar keratosis.Nat Genet. 1999; 23: 421-424https://doi.org/10.1038/70525Crossref PubMed Scopus (395) Google Scholar;Hart et al., 1999Hart T.C. Hart P.S. Bowden D.W. et al.Mutations of the cathepsin C gene are responsible for Papillon–Lefèvre syndrome.J Med Genet. 1999; 36: 881-887PubMed Google Scholar,Hart et al., 2000aHart T.C. Hart P.S. Michalec M.D. et al.Haim–Munk syndrome and Papillon–Lefèvre syndrome are allelic mutations in cathepsin C.J Med Genet. 2000; 37: 88-94Crossref PubMed Scopus (173) Google Scholar). This gene consists of a total of seven exons and the corresponding mRNA, 1.8 kb, encodes a polypeptide of 463 amino acids. The deduced polypeptide consists of a 24 amino acid signal peptide, a 206 amino acid propeptide, and 233 amino acid mature enzyme (Rao et al., 1997Rao N.V. Rao G.V. Hoidal J.R. Human dipeptidyl-peptidase I. gene characterization, localization, and expression.J Biol Chem. 1997; 272: 10260-10265Crossref PubMed Scopus (131) Google Scholar). Cathepsin C, also known as dipeptidyl-peptidase I (EC 3.4.14.1), is a lysosomal cysteine proteinase, and apparently plays an important role in intracellular degradation of proteins and in activation of many serine proteinases within immune/inflammatory cells, including polymorphonuclear leukocytes, monocyte-macrophages, and mast cells. In this study, we report CTSC mutations in two families with PLS, and the first polymorphisms in the gene. The proband (I-2, Family 1 in Figure 1) was a 49-y-old female of Puerto Rican origin, with severe periodontitis and characteristic cutaneous findings diagnostic of PLS. Specifically, she had a history of bilateral scaly patches on the feet, palms, and elbows since childhood. She also had premature loss of both deciduous and permanent teeth, which required replacement with dentures at the age of 12 y. She denied recurrent skin or systemic infections. The proband had 10 siblings, three of which (I-3, I-4, and I-5, Family 1 in Figure 1) were similarly affected. For example, the younger brother (I-5) was noted to have yellow, fissured hyperkeratotic palms and soles with slight pseudoainhum. Scaly hyperkeratotic plaques were present in elbows and knees. Histopathology of the brother's (I-5) skin from right elbow and right palm revealed confluent parakeratosis, tortuous capillaries in the dermal papillae, and a sparse infiltrate of lymphocytes around venules of the superficial plexus, changes reported to be indistinguishable from psoriasis (Angel et al., 2001Angel T.A. Hsu S. Kornbleuth S.I. Kornbleuth J. Kramer E.M. Papillon–Lefèvre syndrome: a case report of four affected siblings.J Am Acad Dermatol. 2001Google Scholar). The proband's parents were dead but they were not known to have skin or dental findings similar to their affected children, and there was known parental consanguinity. The proband at the time of initial examination was a 4-y-old female, the second child of consanguineous Japanese parents (II-2, Family 2 in Figure 1). She had an older, clinically unaffected brother (II-1), whereas a younger brother, 1 y of age (II-3), was clearly affected. The parents were clinically normal, and the inheritance was therefore consistent with an autosomal recessive pattern. The affected children had erythematous hyperkeratotic lesions, which were first noted on their feet at 4 mo of age, and the lesions subsequently developed on their hands, elbows, and knees (Figure 2a–d). Histopathology of the skin from the proband's brother (II-3) at the age of 5 y revealed acanthosis with hyperkeratosis and parakeratosis (Figure 3). There was evidence of follicular hyperkeratosis. The proband also had a history of a liver abscess at the age of 5 y.Figure 3Histopathologic findings in a skin biopsy from the knee of individual II-3 of Family 2 at the age of 5 y. Note acanthosis and hyperkeratosis with follicular hyperkeratosis, parakeratosis, and perivascular inflammatory cell infiltrates (scale bar: 300 μm; hematoxylin and eosin stain).View Large Image Figure ViewerDownload (PPT) At the current age of 24 and 21 y, the two individuals with skin lesions (II-2 and II-3) have minimal dental complaints and do not display overt tooth loss. Panoramic X-ray examination of the teeth ov the affected male (II-3), however, revealed extensive alveolar resorption (Figure 2e). Examination of his older sister's (II-2) teeth revealed similar but less pronounced changes (not shown). Leukocyte function studies, including neutrophil killer activity and neutrophil phagocytic activity, were essentially normal (87% and 92%-95% of the controls) in both patients at 24 and 21 y of age. Among the nine lymphocyte surface markers tested, the affected sister's (II-2) values were well within the normal range, whereas some of the affected brother's (II-3) values (and specifically those for CD56, SD11b, CD11c, CD 57, and CD 16) were at the lower end of the normal values or just below the lower limit. DNA was isolated from peripheral blood specimens from the probands and other available members of the nuclear families, as indicated in Figure 1, by phenol-chloroform extraction using standard procedures (Sambrook et al., 1989Sambrook J. Fritsch E.F. Maniatis T. Molecular Cloning: a Laboratory Manual. Cold Spring Harbor Laboratory Press, Plainview, NY1989: 9.16-9.19Google Scholar). Control DNA was obtained from 50 unrelated individuals with no evidence of a skin disease. DNA was used as a template for polymerase chain reaction (PCR) amplification of exons for mutation detection analysis. The PCR amplification of CTSC exons and of flanking intronic sequences was performed using primers as previously indicated (Toomes et al., 1999Toomes C. James J. Wood A.J. et al.Loss-of-function mutations in the cathepsin C gene result in periodontal disease and palmoplantar keratosis.Nat Genet. 1999; 23: 421-424https://doi.org/10.1038/70525Crossref PubMed Scopus (395) Google Scholar), except for the following newly developed primer pairs for exons 1 and the 5′ half of exon 7: exon 1F, 5′-TCTTCACC- TCTTTTCTCAGC-3′ exon 1R, 5′-GGTCCCCGAATCCAGTC- AAG-3′ exon 7-1F, 5′-TAAGCAGAGATACAGAGAAG-3′ exon 7-1R, 5′-GTAGTGGAGGAAGTCATCATATAC-3′. The PCR reactions were performed in a total volume of 50 μl containing 1 × PCR buffer and 1.25 U of Amplitaq polymerase (Perkin-Elmer Cetus, Foster City, CA), in the presence of 4% dimethyl sulfoxide, 12.8 pmol of each primer, and 200 ng of genomic DNA. The amplification conditions were as follows: 5 min at 94°C for one cycle, followed by 38 cycles of 45 s at 94°C, 45 s at the annealing temperature of the primers (exon 1, 55°C; exon 7-1, 53°C), and 45 s at 72°C in a thermal cycler (Hybaid, Teddington, U.K.). Five microliter aliquots of the PCR products were analyzed by 2% agarose gel electrophoresis. PCR products were directly sequenced by using an ABI Prism 377 automated sequencing system (Perkin-Elmer Cetus). Verification of the mutation was performed by digestion of PCR products amplified from DNA obtained from the probands and his/her immediate family members by restriction endonucleases. The PCR products were digested at 37°C for AciI or MnlI for 15 h. The fragments were examined on 3% or 3.5% agarose gel. In Family 1, screening of CTSC for pathogenetic mutations revealed that the four affected individuals were homozygous for a G→C substitution at the nucleotide position 116 (Figure 4). A clinically unaffected child (II-1) of an affected individual (I-4) was a heterozygous carrier of this mutation (Figure 4). This novel nucleotide substitution resulted in a change from tryptophan (TGG) to serine (TCG) at the0amino acid position 39, and this mutation was designated W39S (Table 1). This novel amino acid substitution mutation affects an evolutionarily conserved tryptophan residue. The nucleotide substitution also creates a new restriction enzyme site for MnlI, which was used for verification of the mutation in this family. MnlI digestion also revealed that an unaffected older brother (I-1) is not a carrier of this mutation (Figure 4). Screening of 100 chromosomes in healthy, unrelated control subjects by MnlI digestion demonstrated the absence of the W39S mutation, suggesting that it was indeed pathogenetic.Table 1Nucleotide variations in the CTSC geneLocationNucleotide positionaNucleotide numbers refer to the open reading frame, the translation-initiation codon (ATG) being +1/+3 in CTSC cDNA sequence (GenBank accession no. NM001814).Nucleotide changeAmino acid substitutionRestriction enzyme siteAllele frequenciesMutations Exon 1 (Family 1)116G (Trp) → C (Ser)W39SMnll– Exon 7 (Family 2)901G (Gly) → A (Ser)G301SAcll–Polymorphisms Intron 1172 + 106G→ A–HaeIII0.714/0.286 Exon 71173T (Thr) → G (Thr)T391TBsll0.953/0.047 Exon 71357A (Ile) → G (Val)I453VMsll0.953/0.047a Nucleotide numbers refer to the open reading frame, the translation-initiation codon (ATG) being +1/+3 in CTSC cDNA sequence (GenBank accession no. NM001814). Open table in a new tab Screening of Family 2 for CTSC mutations revealed that the parents (I-1 and I-2) were heterozygous for a G→A substitution at nucleotide position 901, whereas the two affected children (II-2 and II-3) were homozygous for this mutation. This nucleotide substitution resulted in a change from glycine (GGC) to serine (AGC) at the amino acid position 301, and this mutation was designated G301S (Table 1). This mutation has been previously noted in another unrelated family with PLS, and its presence has been excluded from a control population of 200 unrelated healthy control individuals (Toomes et al., 1999Toomes C. James J. Wood A.J. et al.Loss-of-function mutations in the cathepsin C gene result in periodontal disease and palmoplantar keratosis.Nat Genet. 1999; 23: 421-424https://doi.org/10.1038/70525Crossref PubMed Scopus (395) Google Scholar). This nucleotide substitution also abolished a restriction enzyme site for AciI, which was used for verification of the mutation. AciI digestion confirmed that the parents were heterozygous carriers of the mutation whereas the affected individuals were homozygotes. The AciI digestion also revealed that an unaffected brother (II-1) is not a carrier of this mutation. During the search for pathogenetic mutations in these two families, three additional sequence variants were discovered (Table 1). One of them was an intronic nucleotide substitution whereas another was a neutral polymorphism in exon 7 (T391T). The third one, 1357 A→G, substituted an isoleucine in position 543 by a valine (I453V). The allele frequencies of these apparent polymorphisms are indicated in Table 1. In this study, we have identified homozygous missense mutations W39S and G301S in two families with PLS. Discovery of the novel CTSC mutation W39S brings the total number of distinct mutations found in different families with PLS to 15 (Figure 5). Nine of them are missense mutations, whereas five are nonsense mutations or small deletion mutations resulting in premature termination codon for translation. In addition, one family has a splicing mutation (486-1G→A) at the intron 2/exon 3 border. The missense mutations, including W39S, affect critical, highly conserved amino acids (Hart et al., 2000aHart T.C. Hart P.S. Michalec M.D. et al.Haim–Munk syndrome and Papillon–Lefèvre syndrome are allelic mutations in cathepsin C.J Med Genet. 2000; 37: 88-94Crossref PubMed Scopus (173) Google Scholar), and eight out of nine missense mutations reside within the mature enzyme domain of the polypeptides (Figure 5). Also, three of the amino acid substitutions lead to incorporation of a cysteine in the polypeptide. It is conceivable therefore that these missense mutations result in conformational changes that abolish the catalytic activity of the enzyme. In fact, the activity of this enzyme has been shown to be essentially undetectable in peripheral blood leukocytes of affected individuals in two families with PLS as a result of missense mutations V249F and Y347C (Toomes et al., 1999Toomes C. James J. Wood A.J. et al.Loss-of-function mutations in the cathepsin C gene result in periodontal disease and palmoplantar keratosis.Nat Genet. 1999; 23: 421-424https://doi.org/10.1038/70525Crossref PubMed Scopus (395) Google Scholar). The novel missense mutation identified in this study, W39S, was found in homozygous state in all four affected individuals in Family 1, whereas a heterozygous carrier had no evidence of PLS. Furthermore, this mutation was not present in 100 alleles in unrelated control individuals, thus indicating that it is not a polymorphism. This tryptophan residue is precisely conserved in cathepsin C during evolution in various species between humans and Schistosoma japonicum (see Figure 6). Interestingly, however, the W39S mutation resides at the amino-terminal end of the propeptide (Figure 5), which is cleaved off during processing of the polypeptide to mature enzyme (Muno et al., 1993Muno D. Ishidoh K. Ueno T. Kominami E. Processing and transport of the precursor of cathepsin C during its transfer into lysosomes.Arch Biochem Biophys. 1993; 306: 103-110https://doi.org/10.1006/abbi.1993.1486Crossref PubMed Scopus (49) Google Scholar). It is conceivable then that the W39S mutation interferes either with the transport of the proform polypeptide from endoplasmic reticulum to lysosomes or impedes the subsequent proteolytic processing of the polypeptide to mature enzyme. It is of interest that Family 2 with the G301S mutation had clinical features not entirely typical of PLS. Specifically, the two affected individuals in this family had retained their teeth up to their current age of 24 and 21 y whereas classic cases with PLS are edentulous by the age of 15 y. Such late onset of periodontitis has been noted before (Willett et al., 1985Willett L. Gabriel S. Kozma C. Bottomley W. Papillon-Lefèvre: report of a case.J Oral Med. 1985; 40: 43-45PubMed Google Scholar;Brown et al., 1993Brown R.S. Hays G.L. Flaitz C.M. O'Neill P.A. Abramovitch K. White R.R. A possible late onset variation of Papillon–Lefèvre syndrome: report of 3 cases.J Periodontol. 1993; 64: 379-386Crossref PubMed Scopus (33) Google Scholar;Fardal et al., 1998Fardal Ø Drangsholt E. Olsen I. Palmar plantar keratosis and unusual periodontal findings: observations from a family of 4 members.J Clin Periodontol. 1998; 25: 181-184Crossref PubMed Scopus (22) Google Scholar). It is also of interest that the specific cathepsin C mutation, Y347C, is associated with severe periodontitis but the individuals homozygous with this mutation have no evidence of syndromic skin manifestations (Hart et al., 2000bHart T.C. Hart P.S. Michalec M.D. et al.Localisation of a gene for prepubertal periodontitis to chromosome 11q14 and identification of a cathepsin C gene mutation.J Med Genet. 2000; 37: 95-101Crossref PubMed Scopus (84) Google Scholar). Finally, another autosomal recessive condition with palmoplantar keratoderma and early periodontal destruction, the Haim–Munk syndrome (OMIM no. 245010), has been shown to be allelic with PLS (Hart et al., 2000aHart T.C. Hart P.S. Michalec M.D. et al.Haim–Munk syndrome and Papillon–Lefèvre syndrome are allelic mutations in cathepsin C.J Med Genet. 2000; 37: 88-94Crossref PubMed Scopus (173) Google Scholar). A recurrent missense mutation, Q286R, in exon 6 of the CTSC gene has been identified in several nuclear families with the Haim–Munk syndrome, all of the same ancestry (Hart et al., 2000aHart T.C. Hart P.S. Michalec M.D. et al.Haim–Munk syndrome and Papillon–Lefèvre syndrome are allelic mutations in cathepsin C.J Med Genet. 2000; 37: 88-94Crossref PubMed Scopus (173) Google Scholar). The same study reported a nonsense mutation, Q286X, in the same codon of CTSC in a family with classic features of PLS (Hart et al., 2000aHart T.C. Hart P.S. Michalec M.D. et al.Haim–Munk syndrome and Papillon–Lefèvre syndrome are allelic mutations in cathepsin C.J Med Genet. 2000; 37: 88-94Crossref PubMed Scopus (173) Google Scholar). Collectively, this phenotypic variability of the CTSC mutations suggests either phenotype/genotype correlations or phenotypic modulation by associated genetic and/or epigenetic factors that are not yet evident from the relatively small cohort of patients. The pathomechanistic implications of absent or markedly reduced cathepsin C activities in PLS are not entirely clear but it has been suggested that lack of functional CTSC may be associated with reduced host response against bacteria in dental plaque and possibly other sites (Oguzkurt et al., 1996Oguzkurt P. Tanyel F.C. Büyükpamukçu N. Hiçsönmez A. Increased risk of pyogenic liver abscess in children with Papillon–Lefèvre syndrome.J Pediat Surg. 1996; 31: 955-956Abstract Full Text PDF PubMed Scopus (33) Google Scholar;Czauderna et al., 1999Czauderna P. Sznurkowska K. Korzon M. Roszkiewicz A. Stoba C. Association of inflammatory pseudotumor of the liver and Papillon–Lefèvre syndrome: case report.Eur J Pediatr Surg. 1999; 9: 343-346Crossref PubMed Scopus (16) Google Scholar). CTSC plays an essential role in activating serine proteinases expressed in the granules of bone marrow derived cells both of myeloid and lymphoid series (McGuire et al., 1993McGuire M.J. Lipsky P.E. Thiele D.L. Generation of active myeloid and lymphoid granule serine proteases requires processing by the granule thiol protease dipeptidyl peptidase I.J Biol Chem. 1993; 268: 2458-2467Abstract Full Text PDF PubMed Google Scholar). These serine proteinases are implicated in a variety of inflammatory and immune processes, including phagocytic destruction of bacteria. In fact, previous leukocyte function studies have suggested depressed neutrophil phagocytic and lytic activity and depressud chemotactic response (Bullon et al., 1993Bullon P. Pascual A. Fernandez-Novoa M.C. Borobio M.V. Muniain M.A. Camacho F. Late onset Papillon–Lefèvre syndrome? A chromosomic, neutrophil function and microbiological study.J Clin Periodontol. 1993; 20: 662-667Crossref PubMed Scopus (54) Google Scholar;Ghaffar et al., 1999Ghaffar K.A. Zahran F.M. Fahmy H.M. Brown R.S. Papillon–Lefèvre syndrome: neutrophil function in 15 cases from 4 families in Egypt.Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1999; 88: 320-325Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar;Liu et al., 2000Liu R. Cao C. Meng H. Tang Z. Leukocyte functions in 2 cases of Papillon–Lefèvre syndrome.J Clin Periodontol. 2000; 27: 69-73https://doi.org/10.1034/j.1600-051x.2000.027001069.xCrossref PubMed Scopus (38) Google Scholar). Although these leukocyte functions were well within the normal limits in the two patients in Family 2, a number of lymphocyte surface markers were at the low end of normal values or slightly below the normal limits, suggesting immunologic deficiencies. Mechanistically, deficient activation of leukocyte serine proteinases due to lack of CTSC activity could possibly explain the severe periodontitis in PLS. The mechanisms leading to hyperkeratotic skin lesions are unclear, however. One could speculate that CTSC plays a role in epithelial differentiation leading to characteristic cutaneous findings in PLS. We thank Drs. Sylvia Hsu-Wong and Steven Kornbleuth for clinical assistance. This study was supported by USPHS/NIH Grant PO1 AR38923, and by a grant for clinical research from the Aomori Prefectural Central Hospital.