Evidence of Autoimmune Involvement in the Pathogenesis of Charcot Neuroarthropathy: A Novel Hypothesis with Preliminary Data.

Charcot neuroarthropathy is a devastating condition that places patients at risk for poor outcomes. Although the condition was first described in 1703, knowledge of the causative agent(s) has yet to be fully understood. Recent advances in genetic research have helped to identify potential mechanisms and pathways for the enigmatic destruction and deformities that are often associated with the condition; however, alternative pathways have been proposed. For the purpose of this discussion, we will discuss the human leukocyte antigen, which is one of the most researched contributors to autoimmune pathology and, more recently, has been linked to diabetic complications.

Monogenic disorders as mimics of juvenile idiopathic arthritis.

BACKGROUND: Juvenile idiopathic arthritis is the most common chronic rheumatic disease of childhood. The term JIA encompasses a heterogenous group of diseases. The variability in phenotype of patients affected by the disease means it is not uncommon for mimics of JIA to be misdiagnosed. CASE PRESENTATION: We present four cases who were treated in single tertiary rheumatology centre for JIA who were subsequently diagnosed with a rare monogenic disease. All four patients shared the unifying features of presenting in early childhood and subsequently suffered with refractory disease, not amenable to usual standards of treatment. Multicentric Carpotarsal Osteolysis Syndrome and Camptodactyly-arthropathy-coxa vara-pericarditis syndrome are non-inflammatory conditions and patients typically present with arthropathy, normal inflammatory markers and atypical radiological features. Blau syndrome is an autosomal dominant condition and patients will typically have symmetrical joint involvement with a strong family history of arthritis, signifying the genetic aetiology. CONCLUSIONS: We share our learning from these cases to add to the growing portfolio of JIA mimics and to highlight when to consider an alternative diagnosis. In cases of refractory disease and diagnostic uncertainty further imaging and genetic testing can play a crucial role in establishing the aetiology. In all of these cases the correct diagnosis was made due to careful, longitudinal clinical phenotyping and a close working relationship between rheumatology, radiology and clinical genetics; highlighting the importance of the multidisciplinary team in managing complex patients.

Association between Osteoprotegerin and Charcot Neuroarthropathy: a systematic review.

AIMS: Osteoprotegerin (OPG) has been associated with Charcot Neuroarthropathy (CN); however, three studied OPG polymorphisms (1181C > G, 245A > C and 950 T > C) have yielded conflicting results. Therefore, this meta-analysis was conducted to determine the difference in serum OPG concentrations between healthy controls and diabetics with and without CN and the effect OPG polymorphisms have on CN development. METHODS: PubMed, LILAC, SCOPUS, and EBSCO databases and retrieved publications' bibliographies were searched for studies that examined for OPG and CN. Depending on the heterogeneity, fixed or random effects were used to calculate the pooled odds ratio (OR) or standard difference in means (SDM) with 95% confidence intervals (95%CI) for 5 genetic models (heterozygous, homozygous, dominant, recessive, and allelic) and serum concentrations, respectively. RESULTS: Seven publications (12 studies) demonstrated that serum OPG concentrations were more elevated in subjects with CN (SDM = 0.719, 95%CI = 0.555-0.883, p < 0.001). When CN was compared to healthy controls or diabetics, the difference was more prominent for healthy controls (SDM = 1.043, 95%CI = 0.676-1.409, p < 0.001) than diabetics (SDM = 0.639, 95%CI = 0.456-0.821, p < 0.001) and the SDM difference was significant (p = 0.013). Using 6 publications (9 studies), neither the 1181C > G or the 950 T > C polymorphisms showed any significant associations for any genetic model. For the 245A > C polymorphism, only the homozygous genetic model showed a significant association between the polymorphism and CN (OR = 2.850, 95%CI: 1.051-7.729, p = 0.040). CONCLUSIONS: Here, we determined a potential correlation between the CN and serum OPG concentrations and that only the CC genotype of the 245A > C polymorphism showed an increased risk of developing CN.

The role of genetic factors and monocyte-to-osteoclast differentiation in the pathogenesis of Charcot neuroarthropathy.

Charcot neuroarthropathy is a chronic, progressive condition of the skeletal system that affects some patients with diabetic neuropathy. It results in progressive destruction of bones of the foot and disorganisation of pedal joints and ligaments. Effective prevention and treatment for Charcot neuroarthropathy remain a challenge. Currently, there are no reliable repeatable markers to identify patients with diabetes who are at higher risk of developing Charcot neuroarthropathy. The pathogenesis underlying the development of Charcot neuroarthropathy also remains unclear. In this review, we provide an overview of the history, prevalence, symptoms, risk factors, diagnostics and treatment of Charcot neuroarthropathy. We also discuss the potential for OPG and RANKL gene variants to act as predictive markers for the development of Charcot neuroarthropathy. Finally, we summarise the latest research on the role of monocyte-to-osteoclast differentiation in the development of acute Charcot neuroarthropathy.

Heterotopic ossifications and Charcot joints: Congenital insensitivity to pain with anhidrosis (CIPA) and a novel NTRK1 gene mutation.

Congenital insensitivity to pain with anhidrosis (CIPA), also known as hereditary sensory and autonomic neuropathy type IV (HSAN-IV), is a rare and severe autosomal recessive disorder. We report on an adult female patient whose clinical findings during childhood were not recognized as CIPA. There was neither complete anhidrosis nor a recognizable sensitivity to heat. Tumorlike swellings of many joints and skeletal signs of Charcot neuropathy developed in adolescence which, together with a history of self-mutilation, led to a clinical suspicion of CIPA confirmed by identification of a novel homozygous variant c.1795G > T in the NTRK1 gene in blood lymphocytes. Both parents were heterozygous for the mutation. The variant predicts a premature stop codon (p.Gly599Ter) and thus represents a pathogenic variant; the first reported in the Southeastern European population.

RANKL Gene Polymorphism as a Potential Biomarker to Identify Acute Charcot Foot Among Indian Population With Type 2 Diabetes: A Preliminary Report.

Studies addressing the link between gene polymorphism and Charcot neuropathic osteoarthopathy (CN) have been limited to analyse osteoprotegerin gene. Aim is to understand the association of RANKL gene variants on the susceptibility of diabetic neuropathy and CN and to measure the serum levels of sRANKL among Indian population with type 2 diabetes. 77 subjects (48 males: 29 females) were recruited and divided into 3 groups. Group 1 Control: normal glucose tolerance (NGT). Group 2: Type 2 diabetes mellitus and neuropathy (DPN). Group 3: Established type 2 diabetes mellitus, DPN, and CN. Subjects were genotyped for RANKL SNP 693 C/G and 643 C/T using polymerase chain reaction-restriction fragment length polymorphism. sRANKL levels were measured using ELISA (enzyme-linked immunosorbent assay). The serum levels of sRANKL were significantly different between the 3 groups. In RANKL -643 C/T the frequency of "CT" genotype and the minor allele "T" was greater among the DPN and CN group compared with the NGT. Further statistical analysis found a significant difference in genotypic frequencies between DPN and NGT subjects with CT genotype. In RANK L -693 C/G the frequency of homozygote mutant "GG" and the minor allele "G" was greater among the DPN and CN group compared with the NGT. Significant differences in genomic frequencies were observed among "GG" genotype. RANKL -643 C/T was significantly associated with DPN alone while -693 C/G was significantly associated with both DPN and CN. Thus, the study suggests RANKL polymorphism might be considered as an independent risk factor for the development of CN.

Genotype-phenotype investigation of 35 patients from 11 unrelated families with camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome.

BACKGROUND: The camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP) is a rare autosomal recessive condition characterized by camptodactyly, noninflammatory arthropathy, coxa vara, and pericarditis. CACP is caused by mutations in the proteoglycan 4 (PRG4) gene, which encodes a lubricating glycoprotein present in the synovial fluid and at the surface of articular cartilage. METHODS: In the present study, we compared the clinical and molecular findings of CACP syndrome in 35 patients from 11 unrelated families. In 28 patients, whole exome sequencing was used to investigate genomic variations. RESULTS: We found that camptodactyly of hands was the first symptom presented by most patients. Swelling of wrists, knees, and elbows began before 4 years of age, while the age of joint involvement was variable. Patients reported an increased pain level after the age of 10, and severe hip involvement developed after 20 years old. All patients presented developmental coxa vara and seven patients (~22%) had pleural effusion, pericarditis, and/or ascites. We identified nine novel genomic alterations, including the first case of homozygous complete deletion of exon 1 in the PRG4 gene. CONCLUSION: With this study, we contribute to the catalog of CACP causing variants. We confirm that the skeletal component of this disease worsens with age, and presents the potential mechanisms for interfamily variability, by discussing the influence of a modifier gene and escape from nonsense-mediated mRNA decay. We believe that this report will increase awareness of this familial arthropathic condition and the characteristic clinical and radiological findings will facilitate the differentiation from the common childhood rheumatic diseases such as juvenile idiopathic arthritis.

Prevalence of polymorphisms in OPG, RANKL and RANK as potential markers for Charcot arthropathy development.

Charcot arthropathy is one of the most serious complications of diabetic foot syndrome that leads to amputation of the affected limb. Since there is no cure for Charcot arthropathy, early diagnosis and implementation preventive care are the best available treatment. However, diagnosis is hindered by obscure clinical picture of the disease and lack of molecular markers for its early detection. Results of recent research suggest that OPG-RANKL-RANK axis regulating bone metabolism can be associated with Charcot arthropathy and that SNPs in OPG gene are associated with the disease. Here we report the results of comprehensive analysis of ten SNPs in OPG, RANKL and RANK genes in 260 subjects divided into diabetes, neuropathy and Charcot arthropathy groups. Besides genotype analysis we performed linkage disequilibrium and hierarchical clustering to obtain information about correlation between SNPs. Our results show that OPG 245T/G (rs3134069) and OPG 1217C/T (rs3102734) polymorphisms co-occur in patients with Charcot arthropathy (r2 = 0.99). Moreover, hierarchical clustering revealed a characteristic profile of all SNPs in Charcot arthropathy and neuropathy, which is distinct from control group. Our results suggest that analysis of multiple SNPs can be used as potential marker of Charcot arthropathy and provide insight into possible molecular mechanisms of its development.

Brothers with constrictive pericarditis - A novel mutation in a rare disease.

Familial constrictive pericarditis is extremely rare. We report a case of two brothers both suffering constrictive pericarditis along with having multiple painless joint deformities. Genetic workup confirmed the clinical diagnosis of camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome CACP syndrome and also revealed a rare mutation in the causative gene.

Protein-losing enteropathy in camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome.

BACKGROUND: Camptodactyly-arthropathy-coxa vara-pericarditis (CACP, OMIM: #208250) syndrome is a rare autosomal recessive disease that can be difficult to recognise not only because of its wide clinical variability but also because of its clinical resemblance to juvenile idiopathic arthritis (JIA). PRG4 is the only gene so far known to be associated with CACP syndrome. Children with CACP syndrome lack the glycoprotein lubricin due to recessive mutations in PRG4. Lubricin serves as a lubricant in joints, tendons and visceral cavities (pleural cavity, pericardium) and inhibits synovial proliferation. Children with CACP syndrome suffer from congenital camptodactyly, arthropathy, coxa vara and sometimes pericarditis. This report concerns a child with CACP syndrome complicated by protein-losing enteropathy (PLE), caused by constrictive pericarditis and so contributes to knowledge of the presentation of CACP syndrome. CASE PRESENTATION: A 10- year-old girl with consanguineous parents suffered from congenital camptodactyly and progressive swollen and painful joints. Her father and his sister had similar childhood-onset joint complaints. Laboratory tests showed no signs of inflammation but showed persistent low protein- and IgG- levels, indicating a secondary immunodeficiency. Increased alpha antitrypsin clearance confirmed PLE. Abdominal ultrasound with Doppler showed hepatomegaly and portal hypertension. Echocardiography suggested constrictive pericarditis. However, heart catheterization could not confirm this. Ultrasound and X-ray examination of the joints combined with a puncture of the synovial fluid were performed. These results, combined with the clinical presentation and the consanguinity, suggested CACP syndrome. Due to excessive enteral protein losses, the patient was treated with Cotrimoxazol prophylaxis and immunoglobulin supplements. These supplements were inadequate to achieve normal IgG values. As constrictive pericarditis with subsequent PLE was the best explanation for the excessive IgG losses, pericardiectomy was performed with good results. Genetic testing in our patient was complicated but revealed a pathogenic mutation within the repeat sequence in exon 7 of the PRG4 gene. CONCLUSION: PLE resulting from constrictive pericarditis can be a complication of CACP syndrome. As serious complications can arise from the resulting secondary immunodeficiency, we recommend regular evaluation of clinical symptoms of constrictive pericarditis and PLE in children with CACP syndrome.

A novel compound WISP3 mutation in a Chinese family with progressive pseudorheumatoid dysplasia.

BACKGROUND: Progressive pseudorheumatoid dysplasia (PPD) is an extremely rare autosomal recessive genetic disease caused by mutation of the Wnt1-inducible signaling pathway protein 3 (WISP3) gene. Here, we characterize the clinical manifestations and features of PPD and screen for WISP3 mutations. MATERIALS AND METHODS: We performed genetic testing for PPD in a Chinese family, after investigating the clinical particulars and family history, in addition to 200 healthy individuals, who served as the controls for this study. All 5 exons and the exon-intron boundaries of the WISP3 gene were amplified by polymerase chain reaction (PCR) and sequenced directly. RESULTS: We identified a missense mutation (c.667T>G, p.C223G) in the maternal allele and a nonsense mutation (c.756C>A, p.C252X) in the paternal allele in the two affected individuals. To our knowledge, the mutation c.756C>A has not been reported previously. In these patients, there was a specific period when their condition markedly improved after having been very serious. Moreover, severe compression of lumbar spinal cord led to conspicuous spinal disorders in the proband. CONCLUSIONS: Our study suggests that novel C223G and C252X mutations in exon 4 of the WISP3 gene are responsible for PPD in Chinese patients. Furthermore, we report certain unique phenotypic characteristics in our patients.

Novel WISP3 mutations causing spondyloepiphyseal dysplasia tarda with progressive arthropathy in two unrelated Chinese families.

Spondyloepiphyseal dysplasia tarda with progressive arthropathy (SEDT-PA) is an autosomal recessive skeletal disorder resulting from pathogenic mutations in the Wnt1-inducible signaling pathway protein 3 (WISP3) gene. This disorder predominantly involves the skeletal system, with the leading features of platyspondyly, metaphyseal dysplasia of limbs and extremities, and progressive degeneration of joints. To date, 53 distinct forms of WISP3 mutations have been detected globally, eleven of which originated from Chinese patients. In the current study, we reported the clinical manifestations and radiographic features of two unrelated Chinese SEDT-PA patients. Through genetic analysis, two novel mutations (c.624delA, c.105dupT) as well as one recurrent mutation (c.342T>G) were identified in the WISP3 gene. Our study contributed to the further expansion of the WISP3 mutation spectrum, and demonstrated the genotype-phenotype relationship between mutations in the WISP3 gene and clinical findings of SEDT-PA.

Novel mutations in PRG4 gene in two Indian families with camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome.

BACKGROUND & OBJECTIVES: Camptodactyly--arthropathy-coxa vara-pericarditis (CACP) syndrome is an autosomal recessive disorder caused by mutations in the PRG4 (proteoglycan 4) gene. Hallmarks of the syndrome include congenital or early-onset camptodactyly and arthropathy with synovial hyperplasia, progressive coxa vara deformity and non-inflammatory pericardial effusions. Till date only around 25 pathogenic mutations have been reported in this gene and none have been reported from India. We report here the mutations in the PRG4 gene in three patients of CACP from two unrelated families from India. METHODS: Molecular genetic studies were done for the three patients with the CACP syndrome, from two unrelated Indian families, through sequence analysis of all coding exons and the exon-intron boundaries of the PRG4 gene. RESULTS: Two novel frame-shift deletion mutations leading to premature protein termination were found. One patient was identified to be homozygous for a 2 base pair deletion in exon 6 (c.2645_2646delGA) and the two affected siblings from the other family were found to be homozygous for a 4 base pair deletion in exon 6 (c.2883_2886delAAGA). CONCLUSIONS: This is perhaps the first report of PRG4 mutations from India. Further mutation studies in Indian CACP cases will help to determine the mutation spectrum of the PRG4 gene in the Indian population and also help to further elucidate the molecular pathology and the genotype-phenotype correlation of this rare disease.

CACP syndrome: identification of five novel mutations and of the first case of UPD in the largest European cohort.

Camptodactyly-Arthropathy-Coxa vara-Pericarditis (CACP) syndrome is a rare autosomal recessive disorder caused by mutations in PRG4 gene that encodes for proteoglycan 4, a mucin-like glycoprotein that is the major lubricant for joints and tendon surfaces. The molecular studies reported so far have described the identification of 15 mutations associated with this syndrome and the majority of them were found in families of Arabian origin. Here we report the molecular investigation of the largest European cohort that comprises 13 patients, and allowed the identification of 5 novel mutations and of the first case of CACP syndrome resulting from uniparental disomy of chromosome 1.

[Charcot osteoarthropathy: don't miss it!]. / "Pied de Charcot": un diagnostic à ne pas manquer!

Charcot neuropathic osteoarthropathy (CNO) is a destructive process affecting the bone and joint structure of diabetic patients and resulting from peripheral neuropathy. It is a limb threatening condition resulting in dramatic deformities associated with severe morbi-mortality. The diagnosis is mostly made by the observation of inflammatory signs and higlight the importance of prompt foot evaluation. Imaging studies may help confirm the diagnosis and the severity of the condition but lack of specificity. The goal of the treatment is to maintain or achieve structural stability of the foot and ankle to prevent further deformity and plantar dislocation. The scientific evidences aren't strong enough to recommend bisphosphonates or acute surgical treatment. Surgery is unanimusly recommended to prevent secondary ulceration.

Diagnosis and surgical treatment of progressive pseudorheumatoid dysplasia in an adult with severe spinal disorders and polyarthropathy.

Progressive pseudorheumatoid dysplasia (PPD) is a rare autosomal-recessive disorder. The polyarthritis of PPD has been detailed before. However, the spinal disorder and surgical treatment been rarely mentioned. A 44-year-old patient who has been misdiagnosed as juvenile rheumatoid arthritis (JRA) and given unilateral total hip replacement yet, suffers mainly from severe spinal disorder this time. The platyspondyly, Scheuermann-like lesions of the spine and JRA-like features of the peripheral joints were found on radiographic films, combining negative inflammatory and rheumatoid factors, which most suggested the diagnosis of PPD. As the homozygous nucleotide deletion was found in WISP3 gene, diagnosis of PPD was definite. Neurological examination and further imaging examination indicated severe compression of thoracic and lumbar spinal cord which might lead to his conspicuous spinal disorder. Decompressive laminectomy, posterior fusion and fixation were performed. And an excellent clinical outcome was achieved 1 year after the decompression and fusion: leg pain and hypoesthesia resolved and osseous fusion performed. This is the first reported decompression in the adult spine of PPD. Surgical treatment could receive satisfactory result in PPD, however, it is a palliative therapy which has less help to prevent the development of this disease. Early diagnosis and rehabilitation interventions remain the most important. Clinical, radiographic and genetic features in PPD are crucial in the differential diagnosis.

Camptodactyly-arthropathy-coxavara-pericarditis syndrome in Saudi Arabia: clinical and molecular genetic findings in 22 patients.

BACKGROUND: Camptodactyly-arthropathy-coxavara-pericarditis (CACP) syndrome is a rare autosomal recessive disorder caused by mutations in the gene proteoglycan 4 (PRG4), affecting lubricin production, which is an essential protein for joint function. Manifestations vary between affected individuals with camptodactyly, early-onsetnon-inflammatory arthropathy, coxa vara deformity and non-inflammatory pericarditis. OBJECTIVE: To describe the clinical, laboratory, radiological and genetic findings of CACP syndrome in children from Saudi Arabia. METHODS: Medical records of all the children with CACP syndrome seen between June 1990 and June 2012 at King Faisal Specialist Hospital and Research Center, Riyadh were reviewed. The data include gender,age of first disease manifestations,referral diagnosis, clinical and radiological features, and molecular genetic studies as well as functional status at the last follow-upvisit. RESULTS: Twenty-two patients (15 boys), (clinical and genetic data of 15 patients were previously published) with mean age at diagnosis 3.7 (1-14) years, were included in this cohort study. The referral diagnosis was inaccurate in all patients; juvenile idiopathic arthritis (JIA) was the referral diagnosis in majority of the patients. Six families had more than one affected child. Camptodactyly and large joints arthropathy were present in all the cases. Camptodactyly was observed in the neonatal period in all the patients, while other joint involvement was observed through the 1st year of life. All patients had a normal cardiac evaluation but two children had evidence of pericarditis. All patients had normal inflammatory markers and the result for rheumatoid factor test was negative. Radiological findings included coxa vara with a short femoral neck and flat, irregular femoral heads and intra-osseous cysts, increased joint space, and abnormal modeling of the acetabulum with small iliac wings. Other joints (knees, ankle, elbow and wrist) showed soft-tissue swelling consistent with thick cartilage and abnormal modeling with evidence of intra-articular fluid in majority of the patients. Synovial biopsy from three patients revealed proliferating synovial epithelium with moderate fibro-collagenous densities and multinucleated giant cells, occasional lymphocytes or neutrophils were identified. Previously, a locus responsible for causing CACP syndrome has been reported in eight patients of our cohort; it has been assigned to 1q25-q31. Furthermore, in seven newly diagnosed patients from four unrelated families, five novel mutations were found. All patients were referred to us while they were on NSAIDs, 10 patients used antirheumatic drugs (prednisone and methotrexate) and two patients were treated with etanercept. In all patients, treatment was ineffective apart from mild pain relief. CONCLUSION: CACP syndrome is an autosomal recessive disorder occurring due to mutations in the gene PRG4 encoding lubricin; it is not an uncommon disorder in Saudi Arabia. Pericarditis is rarely seen in our patients. Our data suggest that CACP syndrome may be easily confused with JIA, causing a delay in diagnosis and probably unnecessary treatment with antirheumatic drugs including biologic agents.

Pseudorheumatoid dysplasia. A rare genetic disorder simulating juvenile idiopathic arthritis.

We present the case of a teenage patient with progressive pseudorheumatoid dysplasia, an autosomal recessive disorder that may be initially misdiagnosed as juvenile idiopathic arthritis.

A descriptive analysis of 14 cases of progressive-psuedorheumatoid-arthropathy of childhood from south India: review of literature in comparison with juvenile idiopathic arthritis.

BACKGROUND: Progressive-psuedorheumatoid-arthropathy of childhood (PPAC) is an autosomal recessive single gene skeletal dysplasia involving joints. The gene attributed to its cause is WNT1-inducible-signaling pathway protein3 (WISP3). OBJECTIVE: To study the clinical and radiographic presentation of PPAC in Indian patients and to compare with described features of PPAC and Juvenile Idiopathic Arthritis (JIA) from published literature. METHODS: All cases (n = 14) of PPAC seen in the Rheumatology and Clinical Genetics outpatient clinic between 2008 and 2011 with classical, clinical, and radiological features were studied. The demographic and clinical data were obtained from medical records of the outpatient visits. RESULTS: Slight female preponderance (57%) and history of consanguinity in parents (43%) was observed in this group. The median age at onset was 4.5 years (range from birth to 9 years of age). Early presentation below the age of 3 years was seen in 3/14 patients (21%) in this group. The growth of all the patients fell below the 3rd percentile for the age. Historically, hip joint involvement was the most common presenting feature; however, elbow, wrist, knees, feet, spine, shoulder joints and small joints, namely proximal interphalangeal (PIP), distal interphalangeal (DIP), metacarpophalangeal (MCP), metatarsophalangeal joints (MTP), and interphalangeal joints (IP) of the feet, were also involved, either clinically or radiologically in varying proportions. Platyspondyly was noted in all. Molecular analysis of the WISP3 gene identified mutations in all the 5 individuals in whom it was done. CONCLUSION: This descriptive case series of PPAC from India reports distinctly differentiating clinical, radiological, and molecular markers in contrast with classically described features of JIA, its mimic. Early presentation (age of onset below 3 years) with involvement of interphalangeal joints seen in three patients (21%) was a unique finding, with missense WISP3 gene mutations in all of them. Timely diagnosis of this entity can spare the patient from unnecessary investigations and toxic medications.

Neuroarthropathy secondary to transthyretin amyloidosis (ATTR V30M).

In this article we report the case of a 46-years-old Portuguese woman admitted in our orthopaedic ward with right knee pain. Radiological findings were consistent with neuroarthropathy. After exclusion of the most common causes of polyneuropathy, Familial amyloid polyneuropathy (FAP) was diagnosed by the discovery of a mutation V30M on chromosome 18 by polymerase chain reaction on a fibroblast culture of her skin biopsy. FAP is one of many aetiologies of polyneuropathy. Although a rare disease, genetic screening in selected populations makes early diagnosis and prompt treatment of asymptomatic family members readily available.