Mutation Analysis of the IL36RN Gene in 14 Japanese Patients with Generalized Pustular Psoriasis

Generalized pustular psoriasis (GPP) is a rare, potentially life threatening, and aggressive form of psoriasis, which is characterized by sudden onset with repeated episodic skin inflammation leading to pustule formation. Familial GPP is known to be caused by recessively inherited mutations in the IL36RN gene, which encodes interleukin 36 receptor antagonist (IL‐36Ra). In this article, we performed mutation analysis of the IL36RN gene in 14 Japanese patients with GPP, and identified mutations in two of these patients analyzed. One patient was compound heterozygous for mutations c.115+6T>C and c.368C>G (p.Thr123Arg), whereas the other carried compound heterozygous mutations c.28C>T (p.Arg10*) and c.115+6T>C in the IL36RN gene. Expression studies using total RNA from the patients’ skin revealed that the mutation c.115+6T>C resulted in skipping of exon 3, leading to a frameshift and a premature termination codon (p.Arg10Argfs*1). The protein structure analysis suggested that the missense mutation p.Thr123Arg caused misfolding and instability of IL‐36Ra protein. In vitro studies in cultured cells showed impaired expression of the p.Thr123Arg mutant IL‐36Ra protein, which failed to antagonize the IL‐36 signaling pathway. Our data further underscore the critical role of IL36RN in pathogenesis of GPP.     

Identification of TMC1 as a relatively common cause for nonsyndromic hearing loss in the Saudi population

Hearing loss (HL) is the most common sensory disorder worldwide and genetic factors contribute to approximately half of congenital HL cases. HL is subject to extensive genetic heterogeneity, rendering molecular diagnosis difficult. Mutations of the transmembrane channel‐like 1 (TMC1) gene cause hearing defects in humans and mice. The precise function of TMC1 protein in the inner ear is unknown, although it is predicted to be involved in functional maturation of cochlear hair cells. TMC1 mutations result in autosomal recessive (DFNB7/11) and sometimes dominant (DFNA36) nonsyndromic HL. Mutations in TMC1 are responsible for a significant portion of HL, particularly in consanguineous populations. To evaluate the importance of TMC1 mutations in the Saudi population, we used a combination of autozygome‐guided candidate gene mutation analysis and targeted next generation sequencing in 366 families with HL previously shown to lack mutations in GJB2. We identified 12 families that carried five causative TMC1 mutations; including three novel (c.362+3A > G; c.758C > T [p.Ser253Phe]; c.1396_1398delACC [p.Asn466del]) and two reported mutations (c.100C > T [p.Arg34Ter]; c.1714G > A [p.Asp572Asn]). Each of the identified recessive mutation was classified as severe, by both age of onset and severity of HL. Similarly, consistent with the previously reported dominant variant p.Asp572Asn, the HL phenotype was progressive. Eight families in our cohort were found to share the pathogenic p.Arg34Ter mutation and linkage disequilibrium was observed between p.Arg34Ter and SNPs investigated. Our results indicate that TMC1 mutations account for about 3.3% (12/366) of Saudi HL cases and that the recurrent TMC1 mutation p.Arg34Ter is likely to be a founder mutation.     

The spectrum of BRCA1 and BRCA2 pathogenic sequence variants in Middle Eastern,North African,and South European countries

BRCA1 BRCA2 mutational spectrum in the Middle East, North Africa, and Southern Europe is not well characterized. The unique history and cultural practices characterizing these regions, often involving consanguinity and inbreeding, plausibly led to the accumulation of population‐specific founder pathogenic sequence variants (PSVs). To determine recurring BRCA PSVs in these locales, a search in PUBMED, EMBASE, BIC, and CIMBA was carried out combined with outreach to researchers from the relevant countries for unpublished data. We identified 232 PSVs in BRCA1 and 239 in BRCA2 in 25 of 33 countries surveyed. Common PSVs that were detected in four or more countries were c.5266dup (p.Gln1756Profs), c.181T>G (p.Cys61Gly), c.68_69del (p.Glu23Valfs), c.5030_5033del (p.Thr1677Ilefs), c.4327C>T (p.Arg1443Ter), c.5251C>T (p.Arg1751Ter), c.1016dup (p.Val340Glyfs), c.3700_3704del (p.Val1234Glnfs), c.4065_4068del (p.Asn1355Lysfs), c.1504_1508del (p.Leu502Alafs), c.843_846del (p.Ser282Tyrfs), c.798_799del (p.Ser267Lysfs), and c.3607C>T (p.Arg1203Ter) in BRCA1 and c.2808_2811del (p.Ala938Profs), c.5722_5723del (p.Leu1908Argfs), c.9097dup (p.Thr3033Asnfs), c.1310_1313del (p. p.Lys437Ilefs), and c.5946del (p.Ser1982Argfs) for BRCA2. Notably, some mutations (e.g., p.Asn257Lysfs (c.771_775del)) were observed in unrelated populations. Thus, seemingly genotyping recurring BRCA PSVs in specific populations may provide first pass BRCA genotyping platform.     

Encephalopathy due to defective mitochondrial and peroxisomal fission 2 caused by a novel MFF gene mutation in a young child

Encephalopathy due to defective mitochondrial and peroxisomal fission 2 caused by mitochondrial fission factor (MFF) gene mutation is a rare neurogenetic disorder. Pathogenic MFF mutations have been described in three reports in literature so far. We report a young child of Indian descent who presented to us with global developmental followed by regression of acquired milestones, spasticity, visual and auditory impairment, and was found to harbor a novel pathogenic homozygous MFF truncating variant c.433C>T; p.Arg145Ter. Cellular imaging of patient lymphoblastoid cell line had shown abnormal shapes of mitochondria due to fission defects. The patient has been started on mitochondrial cocktail with some improvement.     

Novel,Compound Heterozygous,Single‐Nucleotide Variants in MARS2 Associated with Developmental Delay,Poor Growth,and Sensorineural Hearing Loss

Novel, single‐nucleotide mutations were identified in the mitochondrial methionyl amino‐acyl tRNA synthetase gene (MARS2) via whole exome sequencing in two affected siblings with developmental delay, poor growth, and sensorineural hearing loss.We show that compound heterozygous mutations c.550C>T:p.Gln 184* and c.424C>T:p.Arg142Trp in MARS2 lead to decreased MARS2 protein levels in patient lymphoblasts. Analysis of respiratory complex enzyme activities in patient fibroblasts revealed decreased complex I and IV activities. Immunoblotting of patient fibroblast and lymphoblast samples revealed reduced protein levels of NDUFB8 and COXII, representing complex I and IV, respectively. Additionally, overexpression of wild‐type MARS2 in patient fibroblasts increased NDUFB8 and COXII protein levels. These findings suggest that recessive single‐nucleotide mutations in MARS2 are causative for a new mitochondrial translation deficiency disorder with a primary phenotype including developmental delay and hypotonia. Identification of additional patients with single‐nucleotide mutations in MARS2 is necessary to determine if pectus carinatum is also a consistent feature of this syndrome.     

Missense mutations in the AFG3L2 proteolytic domain account for ∼1.5% of European autosomal dominant cerebellar ataxias

Spinocerebellar ataxia type 28 is an autosomal dominant form of cerebellar ataxia (ADCA) caused by mutations in AFG3L2, a gene that encodes a subunit of the mitochondrial m‐AAA protease. We screened 366 primarily Caucasian ADCA families, negative for the most common triplet expansions, for point mutations in AFG3L2 using DHPLC. Whole‐gene deletions were excluded in 300 of the patients, and duplications were excluded in 129 patients. We found six missense mutations in nine unrelated index cases (9/366, 2.6%): c.1961C>T (p.Thr654Ile) in exon 15, c.1996A>G (p.Met666Val), c.1997T>G (p.Met666Arg), c.1997T>C (p.Met666Thr), c.2011G>A (p.Gly671Arg), and c.2012G>A (p.Gly671Glu) in exon 16. All mutated amino acids were located in the C‐terminal proteolytic domain. In available cases, we demonstrated the mutations segregated with the disease. Mutated amino acids are highly conserved, and bioinformatic analysis indicates the substitutions are likely deleterious. This investigation demonstrates that SCA28 accounts for ～3% of ADCA Caucasian cases negative for triplet expansions and, in extenso, to ～1.5% of all ADCA. We further confirm both the involvement of AFG3L2 gene in SCA28 and the presence of a mutational hotspot in exons 15–16. Screening for SCA28, is warranted in patients who test negative for more common SCAs and present with a slowly progressive cerebellar ataxia accompanied by oculomotor signs. Hum Mutat 31:1–8, 2010. © 2010 Wiley‐Liss, Inc.     

PIK3R1 mutations in SHORT syndrome

SHORT syndrome (OMIM 269880) is a rare autosomal‐dominant disorder characterized by short stature, hyperextensibility of joints, hernias, ocular depression, ophthalmic anomalies (Rieger anomaly, posterior embryotoxon, glaucoma), teething delay, partial lipodystrophy, insulin resistance and facial dysmorphic signs. Heterozygous mutations in PIK3R1 were recently identified in 14 families with SHORT syndrome. Eight of these families had a recurrent missense mutation (c.1945C>T; p.Arg649Trp). We report on two unrelated patients with typical clinical features of SHORT syndrome and additional problems such as pulmonary stenosis and ectopic kidney. Analysis of PIK3R1 revealed the mutation c.1945C>T; p.Arg649Trp de novo in both patients. These two patients not only provide additional evidence that PIK3R1 mutations cause SHORT syndrome, but also broaden the clinical spectrum of this syndrome and further confirm that the amino acid exchange c.1945C>T; p.Arg649Trp is a hotspot mutation in this gene.     

Schuurs‐Hoeijmakers syndrome in a patient from India

Schuurs‐Hoeijmakers syndrome (SHMS), or Autosomal Dominant Mental Retardation Syndrome type 17 (MRD17) is a rare form of intellectual disability with distinct facial features. A recurrent de novo heterozygous c.607C>T, p.Arg203Trp mutation in the PACS1 gene accounts for all reported cases except for one patient with a de novo heterozygous c.608G>A, p.Arg203Trp mutation. Ethnic background is known to affect the clinical manifestation of dysmorphic syndromes. Here we describe the first Indian patient with Schuurs‐Hoeijmakers syndrome (SHMS) with a de novo heterozygous NM_018026.3 (PACS1):c.607C>T (p.Arg203Trp) variant. He is the only child with SHMS with a cleft lip. Thus our report expands the phenotypic spectrum of SHMS and establishes its occurrence across populations.     

Identification of a founder variant AAGAB c.370C>T,p.Arg124Ter in patients with punctate palmoplantar keratoderma in Southern Denmark

Palmoplantar keratoderma (PPK) is a heterogeneous group of rare skin diseases characterized by hyperkeratosis on the palms or soles. The subtype isolated punctate PPK is caused by heterozygous variants in AAGAB. We investigated if the variant AAGAB c.370C>T, p.Arg124Ter in patients with punctate PPK in the Region of Southern Denmark represented a founder variant and estimated the age to the most recent common ancestor. We performed haplotype analysis on samples from 20 patients diagnosed with punctate PPK and the AAGAB c.370C>T, p.Arg124Ter variant. Using the Gamma Method, we calculated the years to the most recent common ancestor. We also explored the presence of the variant in other populations through literature and databases (HGMD, ClinVar, and gnomAD). Our analysis revealed a shared haplotype of 3.0 Mb, suggesting shared ancestry. The ancestral haplogroup was estimated to an age of 12.1 generations (CI: 4.9–20.3) equivalent to approximately 339 years (CI: 137–568). This study confirms that the frequently observed variant AAGAB c.370C>T, p.Arg124Ter in punctate PPK among patients in the Region of Southern Denmark is caused by a founder variant. We recommend testing for the variant as initial screening in our region and potentially for all Danish patients presenting with punctate PPK.     

Distinct impacts of bi‐allelic WNT10A mutations on the permanent and primary dentitions in odonto‐onycho‐dermal dysplasia

Odonto‐onycho‐dermal dysplasia (OODD) is a rare autosomal recessive syndrome characterized by multiple ectodermal abnormalities. Mutations of the wingless‐type MMTV integration site family member 10A (WNT10A) gene have been associated with OODD. To date, only 11 OODD‐associated WNT10A mutations have been reported. In this report, we Characterized the clinical manifestations with focusing on dental phenotypes in four unrelated OODD patients. By Sanger sequencing, we identified five novel mutations in the WNT10A gene, including two homozygous nonsense mutations c.1176C>A (p.Cys392*) and c.742C>T (p.Arg248*), one homozygous frame‐shift mutation c.898‐899delAT (p.Ile300Profs*126), and a compound heterozygous mutation c.826T>A (p.Cys276Ser) and c.949delG (p.Ala317Hisfs*121). Our findings confirmed that bi‐allelic mutations of WNT10A were responsible for OODD and greatly expanded the mutation spectrum of OODD. For the first time, we demonstrated that bi‐allelic WNT10A mutations could lead to anodontia of permanent teeth, which enhanced the phenotypic spectrum of WNT10A mutations. Interestingly, we found that bi‐allelic mutations in the WNT10A gene preferentially affect the permanent dentition rather the primary dentition, suggesting that the molecular mechanisms regulated by WNT10A in the development of permanent teeth and deciduous teeth might be different.     

PLA2G6 mutations associated with a continuous clinical spectrum from neuroaxonal dystrophy to hereditary spastic paraplegia

PLA2G6‐associated neurodegeneration (PLAN) and hereditary spastic paraplegia (HSP) are 2 groups of heterogeneous neurodegenerative diseases. In this study, we report PLA2G6 gene mutations in 3 families from Turkey, Morocco, and Romania. Two affected Turkish siblings presenting HSP adds the disease to PLAN phenotypes. They were homozygous for the PLA2G6 missense c.2239C>T, p.Arg747Trp variant and the ages of onset were 9 and 21. Parkinsonism, dystonia or cognitive decline were not the clinical elements in these patients contrary to the cases that has been previously reported with the same variant, however, iron accumulation was evident in their cranial magnetic resonance imaging. The Moroccan patient was homozygous for a novel missense c.1786C>T, p.Leu596Phe variant and the Romanian patient had 2 novel mutations; c.1898C>T, p.Ala633Val and c.1765_1768del, p.Ser589ThrfsTer76. Both of these patients conformed better to childhood onset PLAN with the age of onset at 4 and 7 years, respectively. Interestingly, all identified mutations were affecting the highly conserved patatin‐like phospholipase domain of the PLA2G6 protein.     

Ex vivo splicing assays of mutations at noncanonical positions of splice sites in USHER genes

Molecular diagnosis in Usher syndrome type 1 and 2 patients led to the identification of 21 sequence variations located in noncanonical positions of splice sites in MYO7A, CDH23, USH1C, and USH2A genes. To establish experimentally the splicing pattern of these substitutions, whose impact on splicing is not always predictable by available softwares, ex vivo splicing assays were performed. The branch‐point mapping strategy was also used to investigate further a putative branch‐point mutation in USH2A intron 43. Aberrant splicing was demonstrated for 16 of the 21 (76.2%) tested sequence variations. The mutations resulted more frequently in activation of a nearby cryptic splice site or use of a de novo splice site than exon skipping (37.5%). This study allowed the reclassification as splicing mutations of one silent (c.7872G>A (p.Glu2624Glu) in CDH23) and four missense mutations (c.2993G>A (p.Arg998Lys) in USH2A, c.592G>A (p.Ala198Thr), c.3503G>C [p.Arg1168Pro], c.5944G>A (p.Gly1982Arg) in MYO7A), whereas it provided clues about a role in structure/function in four other cases: c.802G>A (p.Gly268Arg), c.653T>A (p.Val218Glu) (USH2A), and c.397C>T (p.His133Tyr), c.3502C>T (p.Arg1168Trp) (MYO7A). Our data provide insights into the contribution of splicing mutations in Usher genes and illustrate the need to define accurately their splicing outcome for diagnostic purposes. Hum Mutat 31:1–9, 2010. © 2010 Wiley‐Liss, Inc.     

Unilateral vestibular schwannoma and meningiomas in a patient with PIK3CA‐related segmental overgrowth: Co‐occurrence of mosaicism for 2 rare disorders

A 28‐year‐old female with PIK3CA‐related segmental overgrowth presented with headaches. She also had a unilateral vestibular schwannoma (VS), as well as 3 small (<2 cm) meningiomas, which according to the Manchester consensus diagnostic criteria for neurofibromatosis 2 (NF2) is sufficient for a clinical diagnosis. Analysis of blood revealed a mosaic PIK3CA c.2740G>A (p.Gly914Arg) mutation, confirming the diagnosis of PIK3CA‐related overgrowth, but no mutations in NF2 were detected. Although VS has not previously been reported in PIK3CA‐related segmental overgrowth, meningiomas have, raising the question of whether this patient's VS and meningiomas represent coincidental NF2 or phenotypic extension of her overgrowth syndrome. Genetic analysis of the VS revealed a heterozygous NF2 mutation c.784C>T (p.Arg262Ter) and loss of a portion of 22q, including NF2, SMARCB1, and LZTR1 genes. These results suggest that the patient has 2 different mosaic disorders, NF2 and PIK3CA‐related overgrowth. The PIK3CA mutation was also present in the VS. Confirmation of the clinical diagnosis of mosaic NF2 in this patient has implications for monitoring and highlights the possibility of co‐occurrence of mosaicism for multiple rare disorders in a single patient.     

Worldwide distribution of common IDUA pathogenic variants

Mucopolysaccharidosis type I (MPS I) is a rare disorder caused by deleterious sequence variants in the α‐L‐iduronidase (IDUA) gene. More than 200 pathogenic variants have been described so far, but their frequencies have not yet been analyzed on a worldwide scale. To address this, we analyzed the genotypes of MPS I patients from 35 published studies papers. The most common pathogenic variant observed was p.Trp402Ter. With frequencies of up to 63%, it was the major allele in most European countries, America and Australia. The variant p.Gln70Ter was also frequent; it was found mainly in Northern and Eastern Europe. The most frequent variant in North African countries was p.Pro533Arg; in Morocco, it represented more than 90% of mutant alleles. Variants observed in East Asians were not found in Western populations, including c.1190‐1G>A, p.Ala79Val, p.Leu346Arg and c.613_617dupTGCTC. Conversely, p.Trp402Ter and p.Pro533Arg were not found in patients from East Asia. In conclusion, the most common pathogenic IDUA variant in MPS I patients are p.Trp402Ter, p.Gln70Ter and p.Pro533Arg. Knowledge about the genetic background of MPS I for each population is essential when developing new genotype‐targeted therapies, as well as to enable faster genetic analysis and improve patient management.     

Identification of seven novel SMPD1 mutations causing Niemann–Pick disease types A and B

Niemann–Pick disease (NPD) types A and B are autosomal, recessively inherited, lysosomal storage disorders caused by deficient activity of acid sphingomyelinase (E.C. 3.1.4.12) because of mutations in the sphingomyelin phosphodiesterase‐1 (SMPD1) gene. Here, we present the molecular analysis and clinical characteristics of 15 NPD type A and B patients. Sequencing the SMDP1 gene revealed eight previously described mutations and seven novel mutations including four missense [c.682T>C (p.Cys228Arg), c.1159T>C (p.Cys387Arg), c.1474G>A (p.Gly492Ser), and c.1795C>T (p.Leu599Phe)], one frameshift [c.169delG (p.Ala57Leufs*20)] and two splicing (c.316+1G>T and c.1341delG). The most frequent mutations were p.Arg610del (21%) and p.Gly247Ser (12%). Two patients homozygous for p.Arg610del and initially classified as phenotype B showed different clinical manifestations. Patients homozygous for p.Leu599Phe had phenotype B, and those homozygous for c.1341delG or c.316+1G>T presented phenotype A. The present results provide new insight into genotype/phenotype correlations in NPD and emphasize the difficulty of classifying patients into types A and B, supporting the idea of a continuum between these two classic phenotypes.     

Identification and functional characterization of two missense mutations in NDRG1 associated with Charcot‐Marie‐Tooth disease type 4D

Charcot‐Marie‐Tooth disease type 4D (CMT4D) is an autosomal‐recessive demyelinating form of CMT characterized by a severe distal motor and sensory neuropathy. NDRG1 is the causative gene for CMT4D. To date, only four mutations in NDRG1 —c.442C>T (p.Arg148*), c.739delC (p.His247Thrfs*74), c.538‐1G>A, and duplication of exons 6–8—have been described in CMT4D patients. Here, using targeted next‐generation sequencing examination, we identified for the first time two homozygous missense variants in NDRG1, c.437T>C (p.Leu146Pro) and c.701G>A (p.Arg234Gln), in two Chinese CMT families with consanguineous histories. Further functional studies were performed to characterize the biological effects of these variants. Cell culture transfection studies showed that mutant NDRG1 carrying p.Leu146Pro, p.Arg148*, or p.Arg234Gln variant degraded faster than wild‐type NDRG1, resulting in lower protein levels. Live cell confocal microscopy and coimmunoprecipitation analysis indicated that these variants did not disrupt the interaction between NDRG1 and Rab4a protein. However, NDRG1‐knockdown cells expressing mutant NDRG1 displayed enlarged Rab4a‐positive compartments. Moreover, mutant NDRG1 could not enhance the uptake of DiI‐LDL or increase the fraction of low‐density lipoprotein receptor on the cell surface. Taken together, our study described two missense mutations in NDRG1 and emphasized the important role of NDRG1 in intracellular protein trafficking.     

Mutation Update and Review of Severe Methylenetetrahydrofolate Reductase Deficiency

Severe 5,10‐methylenetetrahydrofolate reductase (MTHFR) deficiency is caused by mutations in the MTHFR gene and results in hyperhomocysteinemia and varying severity of disease, ranging from neonatal lethal to adult onset. Including those described here, 109 MTHFR mutations have been reported in 171 families, consisting of 70 missense mutations, 17 that primarily affect splicing, 11 nonsense mutations, seven small deletions, two no‐stop mutations, one small duplication, and one large duplication. Only 36% of mutations recur in unrelated families, indicating that most are “private.” The most common mutation is c.1530A>G (numbered from NM_005957.4, p.Lys510 = ) causing a splicing defect, found in 13 families; the most common missense mutation is c.1129C>T (p.Arg377Cys) identified in 10 families. To increase disease understanding, we report enzymatic activity, detected mutations, and clinical onset information (early, <1 year; or late, >1 year) for all published patients available, demonstrating that patients with early onset have less residual enzyme activity than those presenting later. We also review animal models, diagnostic approaches, clinical presentations, and treatment options. This is the first large review of mutations in MTHFR, highlighting the wide spectrum of disease‐causing mutations.     

Varied pathological and therapeutic response effects associated with CHCHD2 mutant and risk variants

Mutations and polymorphic risk variant of coiled‐coil‐helix‐coiled‐coil‐helix domain containing 2 (CHCHD2) have been associated with late‐onset Parkinson disease. In vivo pathological evidence of CHCHD2 mutations is currently lacking. Utilizing transgenic Drosophila model, we examined the relative pathophysiologic effect of the pathogenic (c.182C>T, p.Thr61Ile and c.434G>A, p.Arg145Gln) and the risk (c.5C>T, p.Pro2Leu) CHCHD2 variants. All the transgenic models exhibited locomotor dysfunction that could be exacerbated by rotenone exposure, dopaminergic neuron degeneration, reduction in lifespan, mitochondrial dysfunction, oxidative stress, and impairment in synaptic transmission. However, both mutants showed more severe early motor dysfunction, dopaminergic neuronal loss, and higher hydrogen peroxide production compared with the risk variant. p.Thr61Ile (co‐segregated in three independent PD families) displayed the most severe phenotype followed by p.Arg145Gln (present only in index patient). We treated the transgenic flies with Ebselen, a mitochondrial hydrogen peroxide scavenger compound; Ebselen appears to be more effective in ameliorating motor function in the mutant than the risk variant models. We provide the first in vivo evidence of the pathological effects associated with CHCHD2 mutations. There was a difference in the pathological and drug response effects between the pathogenic and the risk variants. Ebselen may be a useful neuroprotective drug for carriers of CHCHD2 mutations.     

Genetic studies of multiple consanguineous Pakistani families segregating oculocutaneous albinism identified novel and reported mutations

Oculocutaneous albinism (OCA) is an autosomal‐recessive disorder of a defective melanin pathway. The condition is characterized by hypopigmentation of hair, dermis, and ocular tissue. Genetic studies have reported seven nonsyndromic OCA genes, among which Pakistani OCA families mostly segregate TYR and OCA2 gene mutations. Here in the present study, we investigate the genetic factors of eight consanguineous OCA families from Pakistan. Genetic analysis was performed through single‐nucleotide polymorphism (SNP) genotyping (for homozygosity mapping), whole exome sequencing (for mutation identification), Sanger sequencing (for validation and segregation analysis), and quantitative PCR (qPCR) (for copy number variant [CNV] validation). Genetic mapping in one family identified a novel homozygous deletion mutation of the entire TYRP1 gene, and a novel deletion of exon 19 in the OCA2 gene in two apparently unrelated families. In three further families, we identified homozygous mutations in TYR (NM_000372.4:c.1424G > A; p.Trp475*), NM_000372.4:c.895C > T; p.Arg299Cys), and SLC45A2 (NM_016180:c.1532C > T; p.Ala511Val). For the remaining two families, G and H, compound heterozygous TYR variants NM_000372.4:c.1037‐7T > A, NM_000372.4:c.1255G > A (p.Gly419Arg), and NM_000372.4:c.1255G > A (p.Gly419Arg) and novel variant NM_000372.4:c.248T > G; (p.Val83Gly), respectively, were found. Our study further extends the evidence of TYR and OCA2 as genetic mutation hot spots in Pakistani families. Genetic screening of additional OCA cases may also contribute toward the development of Pakistani specific molecular diagnostic tests, genetic counseling, and personalized healthcare.