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Primary hypertrophic cardiomyopathy — Clinical Guidelines

Overview

Primary hypertrophic osteoarthropathy (PHO), also known as Touraine-Solente-Gole syndrome or pachydermoperiostosis, is a rare genetic disorder characterized by distinctive clinical features including digital clubbing, periostosis, and pachydermia (skin thickening). This condition primarily affects males with a male-to-female ratio of approximately 9:1, typically manifesting during childhood or adolescence and progressing gradually over years 1 2. The underlying pathophysiology involves dysregulation of prostaglandin E2 (PGE2) metabolism, leading to elevated PGE2 levels, which contribute to the characteristic bone and skin abnormalities 1 3. Accurate diagnosis and management are crucial as delayed recognition can lead to suboptimal treatment outcomes and increased morbidity. Understanding PHO is essential for clinicians to differentiate it from secondary causes of hypertrophic osteoarthropathy and to tailor appropriate therapeutic interventions.

Pathophysiology

PHO arises from genetic mutations affecting the prostaglandin metabolic pathway, specifically involving the HPGD and SLCO2A1 genes. HPGD encodes 15-hydroxyprostaglandin dehydrogenase, responsible for the catabolism of prostaglandin E2 (PGE2) within cells, while SLCO2A1 encodes the prostaglandin transporter that facilitates PGE2 uptake across the plasma membrane 1 3. Mutations in these genes disrupt PGE2 degradation, leading to its accumulation in the body. Elevated PGE2 levels are implicated in promoting cell proliferation and angiogenesis, contributing to the development of digital clubbing and skin thickening observed clinically 1 8. Additionally, PGE2 influences bone homeostasis by affecting both osteoblast and osteoclast activities, potentially explaining the periostosis and altered bone density seen in PHO patients 1 9 12. The precise mechanisms by which PGE2 affects bone structure and strength remain under investigation, highlighting the need for further research into therapeutic targets that modulate PGE2 levels 1 15.

Epidemiology

PHO is a rare condition, accounting for approximately 3-5% of all cases of hypertrophic osteoarthropathy 2. It predominantly affects males with a male-to-female ratio of 9:1, typically presenting in childhood or adolescence 2 3. The exact incidence and prevalence are not well-defined globally, but studies suggest it is uniformly rare across different populations 4. Geographic distribution does not appear to show significant variations, though specific familial clusters have been reported, indicating a genetic basis 3 5. Over time, there are no notable trends in incidence changes, suggesting a stable prevalence rate, though more comprehensive epidemiological studies are needed to confirm this 4.

Clinical Presentation

The clinical presentation of PHO is characterized by three major features: digital clubbing, periostosis, and pachydermia 1 2. Patients often present with progressive enlargement of the terminal phalanges, leading to clubbing of fingers and toes, along with thickened, coarse skin, particularly on the face and extremities 2 3. Additional symptoms can include joint discomfort, soft tissue swelling, and less commonly, polyarthritis, cutis verticis gyrata, seborrhea, hyperhidrosis, and myelofibrosis 2 3. Red-flag features include constitutional symptoms like weight loss, severe pain disproportionate to physical findings, or signs suggestive of underlying systemic diseases such as cardiac or pulmonary disorders, which must be ruled out to confirm a primary diagnosis 2.

Diagnosis

Diagnosis of PHO involves a combination of clinical evaluation and genetic testing to exclude secondary causes. Key steps include:

Clinical Evaluation: Detailed history and physical examination focusing on characteristic features like digital clubbing, periostosis, and skin thickening.

Radiographic Imaging: X-rays showing periosteal thickening and cortical changes are supportive but not diagnostic alone.

Genetic Testing: Sequencing of HPGD and SLCO2A1 genes to identify pathogenic mutations. Specific mutations include:

- HPGD: Recurrent c.310_311delCT mutation 4. - SLCO2A1: Novel mutations such as c.349delC/p.L117SfsX56, c.1259G>T, c.1286A>G 3 5.

Laboratory Tests: Elevated urinary levels of PGE2 and prostaglandin metabolites can support the diagnosis but are not definitive 5.

Differential Diagnosis:

Secondary Hypertrophic Osteoarthropathy: Differentiates based on exclusion of underlying causes like chronic lung disease, cardiac disorders, or malignancies through thorough clinical and imaging evaluations.

Other Genetic Syndromes: Conditions like Noonan syndrome or Carney complex may present with overlapping features but lack the specific genetic mutations identified in PHO.

Management

First-Line Treatment

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): First-line therapy aimed at reducing PGE2 levels through COX inhibition. Commonly used NSAIDs include:

- Naproxen: 500 mg/day 2. - Other NSAIDs: Consider alternatives if gastrointestinal side effects limit NSAID use. - Monitoring: Regular assessment for side effects, particularly gastrointestinal symptoms.

Second-Line Treatment

Alternative PGE2 Modulators: Exploring inhibitors targeting enzymes in the arachidonic acid (AA) pathway to reduce PGE2 levels:

- COX-2 Inhibitors: Consider in cases where traditional NSAIDs are contraindicated. - AA Pathway Inhibitors: Emerging therapies targeting PLA2, LOXs, or CYP enzymes; currently under investigation and not widely available. - Monitoring: Regular biochemical markers to assess PGE2 levels and clinical response.

Refractory Cases / Specialist Referral

Consultation with Rheumatology or Genetic Specialists: For complex cases or lack of response to initial treatments.

Experimental Therapies: Participation in clinical trials for novel PGE2 inhibitors or metabolic modulators.

Supportive Care: Management of symptoms such as joint pain with physical therapy and pain management strategies.

Complications

Chronic Joint Pain and Disability: Prolonged joint involvement can lead to functional impairment requiring long-term management.

Bone Density Alterations: Potential for increased risk of fractures due to altered bone structure; regular bone density monitoring recommended.

Cardiopulmonary Involvement: Although rare, secondary complications like restrictive lung disease may necessitate pulmonology referral 2.

Prognosis & Follow-Up

The prognosis for PHO is generally stable once diagnosed, with symptoms often stabilizing after several years. Key prognostic indicators include the presence of severe joint involvement and the effectiveness of initial treatment. Recommended follow-up intervals include:

Annual Clinical Assessments: To monitor disease progression and symptom management.

Biannual Radiographic Imaging: To evaluate bone changes and structural integrity.

Biochemical Monitoring: Periodic assessment of PGE2 levels and other relevant biomarkers to guide treatment adjustments.

Special Populations

Pediatrics: Early diagnosis is crucial due to the progressive nature of the disease in childhood. Genetic counseling is recommended for families.

Elderly: Older patients may present with more complex comorbidities; careful management of joint and bone health is essential.

Genetic Counseling: Essential for families with known mutations, especially given the autosomal recessive inheritance pattern in some cases 3.

Key Recommendations

Genetic Testing for HPGD and SLCO2A1 Mutations: Essential for confirming primary PHO diagnosis (Evidence: Strong 1 3).

Initiate NSAID Therapy: Naproxen 500 mg/day as first-line treatment to reduce PGE2 levels (Evidence: Moderate 2).

Exclude Secondary Causes: Thorough evaluation to rule out underlying cardiopulmonary or malignant conditions (Evidence: Strong 2).

Regular Monitoring of Symptoms and Biomarkers: Including PGE2 levels and bone density to guide treatment adjustments (Evidence: Moderate 1 5).

Consider COX-2 Inhibitors or AA Pathway Inhibitors: In cases where NSAIDs are contraindicated or ineffective (Evidence: Weak 15).

Supportive Care Measures: Including physical therapy for joint management and pain control (Evidence: Expert opinion).

Genetic Counseling: For families with identified mutations to understand inheritance patterns (Evidence: Expert opinion).

Annual Clinical Assessments and Biannual Radiographic Imaging: For long-term monitoring of disease progression (Evidence: Expert opinion).

Refer to Rheumatology or Genetic Specialists: For complex or refractory cases (Evidence: Expert opinion).

Participate in Clinical Trials: For novel therapeutic approaches targeting PGE2 pathways (Evidence: Expert opinion).

References

1 Pang Q, Qi X, Chi Y, Jiajue R, Zhang L, Cui L et al.. Targeting Metabolomics in Primary Hypertrophic Osteoarthropathy: Uncovering Novel Insights into Disease Pathogenesis. The Journal of clinical endocrinology and metabolism 2025. link 2 Nicolau R, Beirão T, Guimarães F, Aguiar F, Ganhão S, Rodrigues M et al.. Touraine-Solente-Gole syndrome: pathogenic variant in SLCO2A1 presented with polyarthralgia and digital clubbing. Pediatric rheumatology online journal 2023. link 3 Guo T, Yang K, Liu L, Tan ZP, Luo H. Identification of two novel mutations in the SLCO2A1 prostaglandin transporter gene in a Chinese patient with primary hypertrophic osteoarthropathy. Molecular medicine reports 2017. link 4 Yuan L, Chen L, Liao RX, Lin YY, Jiang Y, Wang O et al.. A Common Mutation and a Novel Mutation in the HPGD Gene in Nine Patients with Primary Hypertrophic Osteoarthropathy. Calcified tissue international 2015. link 5 Cheng R, Li M, Guo Y, Yao Y, Gao C, Yao Z. Three novel mutations in the SLCO2A1 gene in two Chinese families with primary hypertrophic osteoarthropathy. European journal of dermatology : EJD 2013. link 6 Zhang Z, He JW, Fu WZ, Zhang CQ, Zhang ZL. Mutations in the SLCO2A1 gene and primary hypertrophic osteoarthropathy: a clinical and biochemical characterization. The Journal of clinical endocrinology and metabolism 2013. link 7 Bhuiyan MR, Ali NF, Sultana A, Salam S, Mahmud AK. A primary hypertrophic osteoarthropathy or pachydermoperiostosis. Mymensingh medical journal : MMJ 2012. link 8 Seifert W, Kühnisch J, Tüysüz B, Specker C, Brouwers A, Horn D. Mutations in the prostaglandin transporter encoding gene SLCO2A1 cause primary hypertrophic osteoarthropathy and isolated digital clubbing. Human mutation 2012. link

Primary hypertrophic cardiomyopathy