The results of the present study clearly indicate that, among the seven PLS patients studied, mutations in the CTSC gene are observed only in exons 2, 3, 5 and 6. The exons 1, 4 and 7 do not show any mutations in this population.
The mutation spectrum shows that, in exon 2, 5 and 6 only missense mutations and in exon 3 only frame shift insertion are observed. Hence the total numbers of mutations observed in this study are 6. Out of these 5 are missense mutations and 1 is a frame shift insertion.
All the six nucleotide changes reported in this study fulfilled the criteria of a mutation, as these changes were not present in the reference-sequence of the CTSC which encodes for the enzyme dipeptidyl-pentidase 1 (NG_007952.1). In this study total 14 individuals were analyzed for mutations in CTSC gene. Out of 14 the individuals PLS1, PLS2, PLS3, PLS7, PLS8, PLS12 and PLS 13 were exhibiting extreme phenotype of PLS. Rest of the subjects were from the same family but not having any clinical features of PLS. PLS1 – PLS5 belong to family 1, PLS6- PLS8 belong to family 2 and PLS 10–14 belong to family 3.
The missense mutation g.7613A > T was found in exon 2 of PLS 1 which results in amino acid change K2538I. The same mutation was also found in PLS2, PLS10, PLS11, PLS12, PLS13 and PLS14. Further this mutation was found in 4 PLS affected individuals and in 3 non-PLS family members. This may suggest that g.7613A > T may be a recessive mutation causing pathogenicity only in homozygous condition. Moreover, the mutation g.7613A > T is never reported earlier and hence this is a novel mutation reported from South Indian families. The amino acid change K2538I is expected to cause structural alterations of the CTSC protein which may ultimately pave way for the development of PLS.
Similarly mutation g.7890C > A was found in PLS affected individuals PLS1, PLS2, PLS12, PLS13 and also in non-PLS individuals PLS10, PLS11, and PLS14. This mutation is also present in all the family members of the PLS family 1 and 3. This may suggest that a complex interaction of genetics and environment may result in manifestation of clinical features of PLS. Apart from the aforementioned mutations a frame shift mutation g.7580delA was found in PLS10 which is non-PLS subject. Both mutation g.7890C > A and g.7580delA have never been reported and are novel identifications of this study.
PCR products of Exon 3 were analyzed for all the 14 individuals of PLS families g.30126–30127 insA was found in all the affected as well as non-affected members of the PLS families. The insertion was found to cause the frame shift insertion and not leading to any amino acid change as reading frame change. The said frame shift insertion is also never been reported in past published studies. However, this insertion was not found in any family members of PLS 2 family.
The mutation g.42281T > C was found in exon 5 in all the 14 members of the all the PLS families. This is a missense mutation leading to the amino acid change L14094S. This is the novel mutation found in our study in all the family members and never been reported elsewhere. Comparing with the reference sequence it was found that the mutation g.42281T > C is restrict to the Indian PLS family members. The change in amino acid is expected to change the structure of the protein dipeptidyl-pemptidase1. But when the mutation is present in all the affected and non affected PLS individuals it is also suspected that only these mutations are not responsible for causing the phenotypic changes but also some other mutations or expressions of genes are responsible for causing PLS.
In exon 6 of PLS1, mutation g.46325A > G and G46357A > G were found. Both the mutations are missense mutation and leading to the amino acid change E15442G and M15453V respectively. The mutation g.4625A > G is novel mutation found in exon 6 of specimen 1, whereas the mutation g.46357A > G has been already reported in Indian families  and in Spanish families.
The mutation g.46325A > G, g.46357A > G and g.46663C > T were found in specimen 4. Among the 3 mutations in specimen 4. The mutations g.46357A > G and g.46663C > T were already reported in the earlier studies  in Indian families as well as in Turkish families.
In exon 6 of specimen 5, mutation g.46325A > G, g.46357A > G, g.46519G > T and g.46663C > T has been reported. All the 4 mutation were missense mutations and leading to the amino acid change. The mutations g.46357A > G and g.46663C > T were already reported and rest of the two mutations are novel found in our study.
In exon 6 of specimen 6, mutations g.46325A > G, g.46357A > G and g.46519G > T were reported. Among the 3 mutations, mutation g.46357A > G has been already reported and the rest of the two mutations are novel. All the mutations are missense and leading to the aminoacid change E15442G, M15453V and A15507S respectively.
In exon 6 of specimen 7, mutations g.46325A > G, g.46357A > G and g.46519G > T were observed. The mutation g.46325A > G and g.46357A > G were found in the specimen PLS1, PLS4, PLS5, PLS6 and PLS7
An interesting feature of the CTSC gene is that mutations in this gene also result in two other closely related conditions: the Haim-Munk Syndrome , and prepubertal periodontitis. A common clinical manifestation in all three syndromes is severe early-onset periodontitis. Haim-Munk syndrome (HMS) is an ethnically specific disorder described only in Jews of South Indian origin (the so called "Cochin Jews"). The clinical phenotypes of HMS overlap with PLS and prepubertal periodontitis (PPP) and include congenital keratosis palmoplantaris, onychogryposis, periodontitis, pes planus, arachnodactyly, and acroosteolysis. Thus HMS, PPP and PLS seem to be allelic variants. A common mutation c.1040A > G has been shown to cause two distinct phenotypes, PLS and PPP, suggesting that other factors such as genetic or environmental, play a role in the ultimate phenotype. A missense mutation c.857A > G (p.Q286R) in the CTSC gene has been found to cause HMS . This mutation has also been detected in a homozygous state in a Spanish PLS patient, suggesting that the HMS and PLS are clinical variants of the same homozygous cathepsin C gene mutation . It is possible that a part of the clinical manifestations in HMS patients (viz., hyperkeratosis and periodontitis) is caused by a mutation in the CTSC gene where as other features of HMS (viz., onychogryposis, pes planus, arachnodactyly, and acroosteolysis) are caused by mutations in another hitherto undescribed gene. However, this possibility remains to be proven. Hart et al. have carried out genotype-phenotype correlation using 22 probands on whom genotype and phenotype data were available. The categories for genotype were mutations in the pro-region and mutations in the mature enzyme. The categories for phenotypes were the presence or absence of transgressions of the hyperkeratosis lesions on the knees and elbows . No correlation was found as affected subjects with transgressions of dermal lesions onto knees or elbows or both had mutations in both the pro- and mature regions of the enzyme. Our analysis also did not find any correlation between the types of mutations (missense, nonsense, insertion, deletion and splice site) and the presence or absence of the lesions on the knees or elbows or both as observed previously .