Paget’s disease of bone (PDB) is the second most common metabolic bone disorder, after osteoporosis. It is characterised by focal areas of increased and disorganised bone turnover, coupled with increased bone formation. This disease usually appears in the late stages of life, being slightly more frequent in men than in women. It has been reported worldwide, but primarily affects individuals of British descent. Majority of PDB patients are asymptomatic, but clinical manifestations include pain, bone deformity and complications, like pathological fractures and deafness. The causes of the disease are poorly understood and it is considered as a complex trait, combining genetic predisposition with environmental factors. Linkage analysis identified SQSTM1, at chromosome 5q35, as directly related to the disease. A number of mutations in this gene have been reported, pP392L being the most common variant among different populations. Most of these variants affect the ubiquitin-associated (UBA) domain of the protein, which is involved in autophagy processes. Genome-wide association studies enlarged the number of loci associated with PDB, and further fine-mapping studies, combined with functional analysis, identified OPTN and RIN3 as causal genes for Paget’s disease. A combination of risk alleles identified by genome-wide association studies led to the development of a score to predict disease severity, which could improve the management of the disease. Further studies need to be conducted to elucidate other important aspects of the trait, such as its focal nature and the epidemiological changes found in some populations. In this review, we summarize the clinical characteristics of the disease and the latest genetic advances to identify susceptibility genes. We also list current available treatments and prospective options.

Paget disease of bone (PDB) is a focal bone disorder affecting the skeleton segmentally. The main alteration resides in osteoclasts that increase in size, number and activity. Many osteoclasts have cytoplasmic inclusions that have been associated with protein aggregates, increasing the evidences of a possible deregulation of autophagy in the development of the PDB. Autophagy starts with encapsulation of the target into a double-membrane-bound structure called an “autophagosome.” It has been reported that at least 18 ATG genes (autophagy-related genes) are involved in autophagosome formation. We have studied the distribution of genotypes of the ATG2B rs3759601, ATG16L1 rs2241880, ATG10 rs1864183 and ATG5 rs2245214 polymorphisms in a Spanish cohort of subjects with PDB and compared with healthy subjects. Our results show that being a carrier of the C allele of the ATG16L1 rs2241880 and the G allele of ATG5 rs2245214 polymorphisms were associated with an increased risk of developing PDB, whereas being a carrier of the T allele of ATG10 rs1864183 polymorphism decreased the risk of suffering the disease in our series. This is the first report that shows an association between autophagy and Paget Disease of Bone and requires further confirmation in other series.

The objective of this study is to analyze whether IL1β (-511G > A) and IL6 (-174 G > C) polymorphisms are associated with inflammatory activity, radiographic damage or clinical pattern of psoriatic arthritis (PsA). One hundred twenty-five patients classified as PsA according to the Classification of Psoriatic Arthritis (CASPAR) criteria were included. Patients were stratified according to their clinical pattern at inclusion as peripheral, axial, or mixed involvement. Disease activity in peripheral or mixed forms was measured using the number of swollen and tender joints, pain analog visual scale, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and disease activity score 28 (DAS28). Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was used for axial and mixed forms, as were pain visual analog scale, ESR and CRP. Radiographic damage was evaluated using a modified Sharp score and modified stoke ankylosing spondylitis spinal score (SASSSm). The polymorphisms for the promoter region of IL1β (-511 G/A) and IL-6 (-174 G/C) were analyzed. The G allele of IL1B (-511G/A) polymorphism was associated with higher peripheral joint disease activity (OR 3.13; p < 0.0004; CI 95 % 1.43-6.82, p (corrected) <0.008), while the G allele of the IL6 (174G > C) polymorphism presented a strong trend to be associated with peripheral forms (70.86 %) (OR 1.89; p < 0.03; CI 95 % 1.06-3.39, p-corrected 0.05). In addition, this allele showed a lower association with HLA-B27 (15.78 %) compared with C allele (28.57 %) (OR 0.469; p = 0.02; CI 95 % 0.238-0.923, p-corrected 0.03). This study suggests that the G allele polymorphism of IL1B (-511 A/C) is associated with higher peripheral joint disease activity. On the other hand, the IL6 (-174 G/C) polymorphism showed a strong trend to be associated with the peripheral pattern of PsA.

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