Genotype and phenotype characterization of primary hypertrophic osteoarthropathy type 2 and chronic enteropathy associated with SLCO2A1: Report of two cases and literature review.

Autosomal recessive type 2 primary hypertrophic osteoarthropathy (PHOAR2) and chronic enteropathy associated with SLCO2A1 (CEAS) are two entities caused by pathogenic variants (PVs) in the SLCO2A1 gene that can coexist or occur independently from one another. We report two cases of PHOAR2 in Mexico with concomitant CEAS and conducted a review of the literature of the reported cases of PHOAR2 and/or CEAS to analyze the relationship between their genotype and phenotype presentation. The patients from our Institution with classical PHOAR2 phenotype and CEAS, harbored SLCO2A1 c.547G > A and c.1768del variants. We reviewed 232 cases, of which 86.6% were of Asian origin, and identified 109 different variants in SLCO2A1. Intron 7, exon 13, and exon 4 were predominantly affected. The two most common PVs were c.940 + 1G > A and c.1807C > T. We found a statistically significant association between SLCO2A1 variants located in intron 7, exons 12, and 13 and the development of CEAS. Missense variants were more frequent in isolated PHOAR2, while a greater proportion of protein-truncating variants (PTVs) were found in CEAS. Further investigation is imperative to elucidate the underlying pathophysiological mechanisms associated with CEAS, thereby facilitating the identification of effective therapeutic interventions.

[Genetic analysis of a child with Primary hypertrophic osteoarthropathy].

OBJECTIVE: To explore the genetic etiology of a child with Primary hypertrophic osteoarthropathy. METHODS: A child who was admitted to Zhongnan Hospital of Wuhan University on July 27, 2021 was selected as the study subject. Genomic DNA was extracted from peripheral blood samples of the child and his parents and subjected to whole exome sequencing. Suspected splicing variant was verified by Sanger sequencing of family members. In vitro function was validated through a minigene assay, whilst the suspected exonic deletion was validated by long-fragment PCR. RESULTS: Whole exome sequencing revealed that the child has harbored compound heterozygous variants of HPGD gene, including a heterozygous deletion (exon 3 del) derived from his father and a splicing variant (c.421+1G>T) derived from his mother. Long-fragment PCR verified that the child and his father had both harbored a 7 565 bp heterozygous deletion (c.218-1304_324+6156del), whilst the minigene assay proved that the splicing variant has resulted in skipping of exon 4. CONCLUSION: The heterozygous c.218-1304_324+6156del deletion and the c.421+1G>T splicing variant of the HPGD gene probably underlay the pathogenesis in this child. Above finding has enriched the mutational spectrum of the HPGD gene and provided a basis for genetic counseling and prenatal diagnosis for this family.

Primary Hypertrophic Osteoarthropathy Mimicking Juvenile Idiopathic Arthritis: A Novel SLCO2A1 Mutation and Imaging Findings.

Primary hypertrophic osteoarthropathy (PHO), also known as pachydermoperiostosis, is a rare, multisystemic, autosomal recessive condition typically presenting with digital clubbing, osteoarthropathy, and various skin manifestations. Radiographs show distinctive periosteal reaction and thickening along the long bones. PHO is caused by homozygous mutations in the HPGD gene in chromosome 4q34.1 or the SLCO2A1 gene in 3q22.1q22.2. Here, we report on a 20-year-old male with enlarged and swollen joints with arthralgia, palmoplantar hyperhidrosis, and large hands and feet with marked digital clubbing. We also present radiographic, MRI, and ultrasonographic features of the case. These clinical and imaging findings were compatible with the diagnosis of PHO, and a novel homozygous mutation, c.576C>G, p.Ile192Met, was found in SLCO2A1.

Novel SLCO2A1compound heterozygous mutation causing primary hypertrophic osteoarthropathy with Bartter-like hypokalemia in a Chinese family.

PURPOSE: Primary hypertrophic osteoarthropathy (PHO) is an inherited disease characterized by digital clubbing, periostosis and pachydermia with defects in the degradation of prostaglandin E2 (PGE2). Mutations in SLCO2A1 gene-encoding prostaglandin transporter (PGT) resulted in PHO, autosomal recessive 2 (PHOAR2). The spectrum of mutations and variable clinical complications of PHOAR2 has been delineated. In this study, we investigated a Chinese PHO family with a manifestation of Bartter-like hypokalemia. METHODS: Clinical manifestations were collected and genetic analyses were performed in the PHO family. RESULTS: The 33-year-old male proband had severe hypokalemia due to potassium loss from the kidney, while his brother had mild hypokalemia. After being treated with etoricoxib, the serum potassium level of the patient increased rapidly to the normal range which corresponded with the reduction in his serum PGE2 and PE2 metabolite (PGEM) levels. A novel SLCO2A1 compound heterozygous mutation of p.I284V and p.C459R was identified in two PHO patients in this family. CONCLUSIONS: The present findings supported that the Bartter-like hypokalemia is a new complication of PHOAR2 caused by the high level of PGE2. Etoricoxib was demonstrated to be effective for the renal hypokalemia in PHO patients.

A novel mutation in the HPGD gene causing primary hypertrophic osteoarthropathy with digital clubbing in a Pakistani family.

Primary hypertrophic osteoarthropathy (PHO) is a congenital multisystemic entity characterized by three major clinical symptoms: pachydermia, periostosis, and digital clubbing. Recently it has been reported that pathogenic mutations in two genes are known to be associated with PHO: HPGD and SLCO2A1. In the present study, a five-generation consanguineous Pakistani family harboring primary hypertrophic osteoarthropathy in autosomal-recessive pattern was ascertained. Whole genome single nucleotide polymorphisms (SNPs) genotyping and sequence analysis revealed a novel homozygous missense mutation (c.577T˃C) of the human HPGD gene in all affected members of the family. The study presented here demonstrate the first case of primary hypertrophic osteoarthropathy reported in Pashtun population.

A novel homozygous mutation in the SLCO2A1 gene causing pachydermoperiostosis: Efficacy of hydroxychloroquine treatment.

Pachydermoperiostosis (PDP), otherwise known as primary hypertrophic osteoarthropathy, is characterized by digital clubbing, pachydermia and subperiosteal new bone formation. Joint pain, polyarthritis, cutis verticis gyrata, seborrhea, and hyperhidrosis are frequently associated to this condition. We report a 17-year-old boy presented with pain and swelling of knees and ankles, and progressive thickening of skin face with seborrhea from about 4 years. At the admission he also showed digital clubbing of both hands and feet and palmoplantar hyperhidrosis. We hypothesized PDP and molecular analysis confirmed diagnosis showing a novel mutation in a homozygous state in the SLCO2A1 gene coding for prostaglandin transporter. He started therapy with hydroxychloroquine with a great improvement in joint pain and skin conditions. This is the first reported case of PDP who was successfully treated with hydroxychloroquine, with effects not only on arthralgia but also, surprisingly, on skin conditions.

[Identification of a HPGD mutation in three families affected with primary hypertrophic osteoarthropathy].

OBJECTIVE: To detect mutation of HPGD gene among three pedigrees affected with primary hypertrophic osteoarthropathy (PHO) by DNA sequencing and high-resolution melting (HRM) analysis. METHODS: Genomic DNA was extracted from peripheral blood samples collected from the pedigrees. PCR and direct sequencing were carried out to identify potential mutations of the HPGD gene. Amplicons containing the mutation spot were generated by nested PCR. The products were then subjected to HRM analysis using the HR-1 instrument. Direct sequencing was carried out in family members and healthy individuals to confirm the result of HRM analysis. RESULTS: A homozygous mutation c.310_311delCT was detected in 2 affected probands, while a heterozygous mutation c.310_311delCT was detected in the third proband. HRM analysis of the fragments encompassing HPGD exon 3 showed 3 curve patterns representing three different genotypes, i.e., the wild type, the c.310_311delCT homozygote, and the c.310_311delCT heterozygote. Result of DNA sequencing was consistent with that of the HRM analysis and phenotype of the subjects. CONCLUSION: The c.310_311delCT mutation may be the most prevalent mutation among Chinese population. HRM analysis has provided an optimized method for genetic testing of HPGD mutation for its simplicity, rapid turnover and high sensitivity.

[Two cases of primary hypertrophic osteoarthropathy with SLCO2A1 gene mutations].

Two patients with primary hypertrophic osteoarthropathy (PHO) and their available healthy family members were studied. All exons of the SLCO2A1 and HPGD gene and adjacent exon-intron sequences were amplified by PCR and subsequently sequenced. To assess the damaging effects of missense mutations in silico, the online database, PolyPhen-2 and SIFT were used. We identified two homozygous mutations in SLCO2A1 gene: one was c.1106G>A (p.G369D) in exon 9, the other was c.611C>T (p.S204L) in exon 4. No HPGD mutation was found in the affected individuals. The two mutation were predicted in silico by the bioinformatic tools. Our study further supports the role of mutations in the SLCO2A1 gene in the pathogenesis of PHO. Identification of the genotype in PHO may not only help the clinical diagnosis of PHO but also help the interpretation of genetic information for prenatal diagnosis and genetic counseling.

[Genetic analysis of a pedigree with primary hypertrophic osteoarthropathy].

Objective: To analyze the clinical and genetic features of primary hypertrophic osteoarthropathy (PHO). Methods: The clinical data of one Chinese pedigree of PHO, namely pachydermoperiostosis (PDP) were collected.Blood samples were drawn from the propositus and other family members.DNA was extracted and genetic analysis was performed by Sanger method after PCR.The sequencing data of HPGD gene exons were analyzed by alignment with sequences from National Center for Biotechnology Information (NCBI). Results: (1)The propositus represented symptoms in childhood including clubbing fingers, sweating, seborrhea, joint swelling and so on.Periosteal thickening and bone hyperplasia were found by X-ray. (2)The homozygous mutation named c. 310_311delCT in propositus, which located in the third exon of HPGD, was identified.His parents carried the same heterozygous mutation, while his sister did not inherit any mutation of this gene. (3)The prediction of spatial structure of proteins revealed that the mutant proteins had about 60% discrepancy compared with wild-type protein, losing a lot of motifs responsible for combining with coenzyms and prostaglandin E(2), as well as active sites of enzymes. Conclusions: The clinical manifestations and imaging findings are helpful to diagnose PDP. Moreover gene mutation analysis ensures the diagnosis.The structure and function of HPGD gene mutation induce 15-hydroxy prostaglandin dehydrogenase mutation, contributing to the occurrence of PDP.

Pachydermoperiostosis: The value of molecular diagnosis.

BACKGROUND: Pachydermoperiostosis is a rare autosomal recessive genetic disorder characterized by the association of periostosis and pachydermia. To date, two genes involved in prostaglandin metabolism, HPGD and SLCO2A1, have been identified. PATIENTS AND METHODS: A 7-year-old girl presented digital clubbing of the hands and feet, curved nails, hyperhidrosis, and pachydermia, as well as eczema of the trunk and limbs. The diagnosis of pachydermoperiostosis was confirmed by the detection of a homozygous mutation in the HPGD gene. The second case concerned a 41-year-old male with acral and cephalic pachydermia (cutis verticis gyrata), and palmoplantar keratoderma. Bone X-rays showed changes in the distal ends of several bones. The diagnosis of pachydermoperiostosis was confirmed by the detection of a homozygous mutation in the SLCO2A1 gene. DISCUSSION: The genotype/phenotype correlation suggests that patients with SLCO2A1 mutations will develop the symptoms later in life, but that these will be more severe, with a greater likelihood of cutis verticis gyrata and joint involvement compared with patients presenting HPGD mutations. In addition, hereditary enteropathy has recently been described in patients with SLCO2A1 mutations, which could account for the gastrointestinal picture seen in the second patient. Finally, on account of cases involving myelofibrosis associated with mutations in the SLCO2A gene, these patients should have a hematologic follow-up. CONCLUSION: Given the genotype/phenotype correlations illustrated by these cases, it would appear useful to propose molecular diagnosis for patients presenting pachydermoperiostosis.

Identification of the Mutations in the Prostaglandin Transporter Gene, SLCO2A1 and Clinical Characterization in Korean Patients with Pachydermoperiostosis.

Pachydermoperiostosis (PDP), or primary hypertrophic osteoarthropathy, is a rare genetic disease affecting both skin and bones. Both autosomal dominant with incomplete penetrance and recessive inheritance of PDP have been previously confirmed. Recently, hydroxyprostaglandin dehydrogenase (HPGD) and solute carrier organic anion transporter family member 2A1 (SLCO2A1) were reported as pathogenic genes responsible for PDP. Both genes are involved in prostaglandin E2 (PGE2) degradation. We aimed to identify responsible genes for PDP and the clinical features in Korean patients with PDP. Six affected individuals and their available healthy family members from three unrelated Korean families with PDP were studied. All of the patients displayed complete phenotypes of PDP with finger clubbing, pachydermia, and periostosis. Mutation analysis revealed a novel heterozygous mutation in the SLCO2A1 gene at nucleotide 302 causing a substitution of the amino acid isoleucine to serine at codon 101 (p.IIe101Ser) in affected individuals. We also identified known SLCO2A1 mutations, one homozygous for c.940+1G>A, and another compound heterozygous for c.940+1G>A and c.1807C>T (p.Arg603*) from two PDP families. Genetic analyses of the PDP patients showed no abnormality in the HPGD gene. Our study further supports the role of mutations in the SLCO2A1 gene in the pathogenesis of PDP and could provide additional clues to the genotype-phenotype relations of PDP.

Pachydermoperiostosis.

A case of Pachydermoperiostosis (PDP) presented to us in rheumatology clinic with complaints of enlargement and broadening of bilateral hands and feet, grade IV digital clubbing, coarsening of facial features, excessive sweating of the palms, soles during summers.

[Progress in genetic research on pachydermoperiostosis].

Pachydermoperiostosis is a rare genetic disease characterized by finger clubbing, periostosis, cutis verticis gyrata and pachydermia accompanied by acroosteolysis and hyperhidrosis. Recently, two susceptibility genes, HPGD and SLCO2A1, have been identified, whose protein products are involved in the transportation of prostaglandin and metabolism underlying pachydermoperiostosis. Here the genetic basis of pachydermoperiostosis and its correlation with its clinical phenotype are reviewed, which may provide a reference for basic research and clinic diagnosis for the disease.

Exome sequencing identifies SLCO2A1 mutations as a cause of primary hypertrophic osteoarthropathy.

By using whole-exome sequencing, we identified a homozygous guanine-to-adenine transition at the invariant -1 position of the acceptor site of intron 1 (c.97-1G>A) in solute carrier organic anion transporter family member 2A1 (SLCO2A1), which encodes a prostaglandin transporter protein, as the causative mutation in a single individual with primary hypertrophic osteoarthropathy (PHO) from a consanguineous family. In two other affected individuals with PHO from two unrelated nonconsanguineous families, we identified two different compound heterozygous mutations by using Sanger sequencing. These findings confirm that SLCO2A1 mutations inactivate prostaglandin E(2) (PGE(2)) transport, and they indicate that mutations in SLCO2A1 are the pathogenic cause of PHO. Moreover, this study might also help to explain the cause of secondary hypertrophic osteoarthropathy.

A Common Mutation and a Novel Mutation in the HPGD Gene in Nine Patients with Primary Hypertrophic Osteoarthropathy.

Primary hypertrophic osteoarthropathy (PHO) is a hereditary bone disease characterized by digital clubbing, periostosis, and pachydermia. The HPGD gene encoding 15-prostaglandin dehydrogenase and SLCO2A1 encoding one type of prostaglandin transporter were found to be responsible for PHO. Mutations of either gene would lead to increased level of prostaglandin E2 (PGE2), which might contribute to the constellation of the symptoms. The aim of the study was to analyze the HPGD gene and the clinical characteristics in nine patients with the diagnosis of PHO. Nine patients, (eight males and one female) including two siblings and seven sporadic cases, were enrolled in the study. Clinical features were summarized, and blood and urine samples were collected. Sanger method was used to sequence the HPGD gene to detect mutations. Urinary PGE2 and prostaglandin metabolite (PGE-M) levels for each patient were measured and compared to the healthy controls. A recurrent c.310_311delCT mutation was identified in all patients, of which six were homozygous, two were heterozygous, and one was compound heterozygous with this mutation and a novel heterozygous missense mutation c.488G>A (p.R163H). The levels of PGE2 in urine were much higher than normal in all patients, along with lower PGE-M levels. In conclusion, nine PHO patients were characterized by typical clinical manifestations including digital clubbing, periostosis, and pachydermia. A common mutation and a novel mutation in HPGD gene were identified to be responsible for the disease, and c.310_311delCT mutation is likely to be a hot-spot mutation site for Asian PHO patients.

[Genetic diagnosis for a Chinese Han family with primary hypertrophic osteoarthropathy].

OBJECTIVE: To identify the genetic cause for a Chinese Han family affected with primary hypertrophic osteoarthropathy. METHODS: Whole blood and urine samples were collected from a patient and 7 unaffected relatives of the family. The coding sequences and intron/exon boundaries of HPGD and SLCO2A1 genes of the patient were amplified with polymerase chain reaction and sequenced. The genotypes of relatives were subsequently verified. Urinary prostaglandin level was measured with enzyme-linked immunosorbent assay (ELISA). RESULTS: A homozygous 2-bp deletion in HPGD gene (c.310_311delCT, or p.L104AfsX3) was detected in the patient, and 5 heterozygous carriers were identified in the relatives. The urinary prostaglandin E2 (PGE2) level was significantly elevated (P<0.01), while PGE-M was significantly reduced (P<0.01) in the patient. CONCLUSION: Primary hypertrophic osteoarthropathy in this family is caused by a homozygous mutation (c.310_311delCT) in the HPGD gene.

A novel recessive 15-hydroxyprostaglandin dehydrogenase mutation in a family with primary hypertrophic osteoarthropathy.

We present two PHO siblings having a novel homozygous truncating mutation in HPGD. The purpose of the study was to attempt medical treatment, and to find the HPGD mutation causing the disease, in a 22-year old Turkish male and his 23-year old sister afflicted with primary hypertrophic osteoarthropathy (PHO). In combination with NSAIDs and colchicine, treatment with sulfasalazine was started in both cases, and methotrexate was added to the treatment regimen of the female patient at the end of the first year. The patients were found to be typical PHO. Ultrasonographic examination of the joints revealed synovitis and inflammation by B mode and power Doppler ultrasonography. Joint symptoms responded to sulfasalazine treatment in both patients. However, after the addition of methotrexate, the female patient had better remission. All exons of HPGD, the known disease gene, were analyzed by Sanger sequencing. A homozygous 2-bp deletion (c.310_311delCT or p.L104AfsX3) was identified. Seven relatives carrying the mutation in the heterozygous state were examined and none was found affected. Although not specific for this disease, skin, soft tissue and joint ultrasonography can be helpful for evaluation of the musculoskeletal findings in the patients.