Clinical and genetic characteristics of primary hypertrophic osteoarthropathy

Background. Primary hypertrophic osteoarthropathy is a rare genetically heterogeneous disease with three clinical variants. The classic one is a combination of hyperostosis, arthropathy and pachyderma and two variants with damage to only bone structures or pachyderma. Two genes responsible for the occurrence of primary hypertrophic osteoarthropathy have been identified: HPGD (debut age up to one year) and SLCO2A1 (debut in puberty and adolescence), whose products are involved in prostaglandin E2 metabolism. Two recurrent variants were identified in the HPGD gene: c.175_176delCT(p.Leu59fs) in patients from Europe and c.310_311delCT in patients from China. There were no clinical and genetic correlations in patients with different variants in the identified genes, which may be due to a small number of observations. The analysis of clinical manifestations in patients with newly identified variants or previously unidentified combinations of variants in a compound‑heterozygous state helps to understand the pathogenesis and prognosis of the course of the disease.Aim. To present the clinical and genetic characteristics of two Russian patients with primary hypertrophic osteoarthropathy caused by a newly identified combination of nucleotide variants in a compound‑heterozygous state in the HPGD and SLCO2A1 genes.Materials and methods. Clinical examination, radiography of the skeleton and chest, electrocardiography, echocardiography. Confirmation of the pathogenicity of the identified variants and clarification of the type of disease was carried out using automatic Sanger sequencing.Results. The clinical and genetic characteristics of two unrelated patients with primary hypertrophic osteoarthropathy caused by an undescribed combination of variants in the compound heterozygous state in the HPGD and SLCO2A1 genes were analyzed. In a patient with variants in the SLCO2A1 gene, the disease debuts at the age of 14 with deformities of the fingers, nails on the hands and feet, followed by the addition of burning pain in the distal parts of the arms and legs. At the age of 33, the examination revealed deformity of the fingers of the hands and feet by the type of drumsticks and nails by the type of watch glasses, enlargement of the knee joints, pronounced arthralgia. There were no signs of pachyderma. The new generation sequencing revealed two variants in the SLCO2A1 gene c.764G>A(p.Gly255Glu) in exon 6 and c.1333C>T(p.Arg445Cys) in exon 10. These variants were identified earlier in a compound‑heterozygous combination with other variants in patients with the classical phenotype of the disease, which were not present in the patient we observed. A feature of the case was pronounced hyperhidrosis and burning pain in the extremities, which may be due to stimulation of nociceptors in the musculoskeletal structures.Deformities of the fingers, nails of the hands and feet occurred in a patient with variants in the HPGD gene at 6 months. At the age of 9 years, a change in shape, stiffness and arthralgia of the knee and elbow joints without pachyderma were revealed. The identified variant with c.175_176delCT(p.Leu59fs) in this gene is often found in patients from European countries, and the other is c.1A>G(p.Met1?) discovered for the first time.Conclusion. The results allow us to conclude that when we found combinations of two variants in the HPGD and SLCO2A1 genes, there will be no pachyderma in the spectrum of clinical manifestations of primary hypertrophic osteoarthropathy. Sequencing of the new generation exome is the optimal diagnostic method.