1. Definition and Classification

CLOVES syndrome (Congenital Lipomatous Overgrowth, Vascular Malformations, Epidermal Nevi, Skeletal/Spinal Anomalies) is a rare, complex mosaic overgrowth disorder belonging to the broader category of PIK3CA-Related Overgrowth Spectrum (PROS). It results from postzygotic, somatic gain-of-function mutations in the PIK3CA gene (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha), located on chromosome 3q26.32.

• Molecular Mechanism: Pathogenic variants (e.g., H1047R, E545K, Q546K) constitutively activate the PI3K-AKT-mTOR signaling pathway → unregulated cellular growth, metabolism, and angiogenesis.
• Prevalence: Estimated <1:1,000,000; >250 cases reported in literature (as of 2024). Most are sporadic; no inheritance pattern (mosaic, not germline).
• Historical Context: First defined as a distinct clinical entity by Alomari et al. (Plastic and Reconstructive Surgery, 2013) and Saap et al. (American Journal of Medical Genetics, 2013), differentiating it from Klippel–Trenaunay syndrome (KTS), Maffucci syndrome, and Proteus syndrome.

Key Diagnostic Clarification: CLOVES is not a diagnosis of exclusion. Molecular confirmation (PIK3CA mutation in affected tissue) is now considered the gold standard per the International Society for the Study of Vascular Anomalies (ISSVA) 2024 classification update and consensus guidelines from the PROS Expert Network.

2. Clinical Manifestations: Phenotype–Genotype Correlation & Systemic Involvement

Symptoms are highly variable due to mosaicism, mutation timing, and tissue distribution. Most patients present at birth or in early infancy; neonatal presentation is often severe.

A. Soft Tissue Overgrowth & Lipomatous Masses

• Characteristics: Nonencapsulated, infiltrative adipose tissue masses—predominantly paravertebral, lumbar/sacral, and truncal (seen in >85% of cases). Unlike isolated lipomas, these are dysregulated overgrowths with vascular/lymphatic components.
• Clinical Impact: Masses may compress neural structures (e.g., cauda equina syndrome), cause functional impairment (e.g., gait disturbance), or lead to chronic pain. MRI shows T1-hyperintense signal with fat suppression.

B. Vascular & Lymphatic Malformations

• Venous: Dilated, tortuous superficial veins; deep venous anomalies (e.g., hypoplastic iliac veins) increase risk of venous thromboembolism (VTE)—especially during immobilization or surgery.
• Lymphatic: Mixed micro/macro cystic malformations; lymphatic leakage or chyle accumulation in pleural/peritoneal cavities. Lymphatic endothelial proliferation may contribute to protein-losing enteropathy.
• Capillary Malformation (Port-Wine Stain): Often midline or asymmetric; may extend into deep dermis.

C. Skeletal & Spinal Anomalies

• Spinal: Tethered cord (30–45%), diastematomyelia, syringomyelia, vertebral anomalies (hemivertebrae, scoliosis/kyphosis). Early neurosurgical evaluation is mandatory—neurological decline can be insidious.
• Limb Asymmetry: Megalodactyly, macrodactyly (especially fingers/toes), cortical thickening, overgrowth of long bones (tibia/fibula > radius/ulna).
• Pelvic Dysplasia: Asymmetric iliac wings, coxa valga.

D. Genitourinary (GU) & Gastrointestinal (GI) Involvement

• Kidneys: Solitary kidney (20–30%), renal duplication, hydronephrosis. Increased risk of Wilms tumor—though less than in WAGR or Beckwith-Wiedemann; nonetheless, bilateral renal ultrasound every 3 months until age 7 is recommended (per COG and SIOP guidelines).
• Bladder/Bowel: Hematuria (microscopic > gross), vesicoureteral reflux, neurogenic bladder (from tethered cord), enteric fistulae. Protein-losing enteropathy from lymphatic leakage is a life-threatening complication.

E. Dermatologic Features

• Epidermal nevi: Linear or swirled, often along Blaschko’s lines.
• Vascular nevi: Port-wine stains, capillary malformations.

Red Flags for CLOVES vs Mimics:

• Truncal lipomatous overgrowth + ipsilateral limb overgrowth + spinal anomalies = highly specific for CLOVES (PPV >90%).
• Absence of PIK3CA mutation in affected tissue argues against PROS.

3. Diagnosis: Multimodal & Molecularly Confirmed

A. Clinical Diagnostic Criteria (Per ISSVA 2024, Alomari et al.)

At least 3 major features required:

1. Congenital truncal lipomatous overgrowth
2. Vascular malformation (venous/lymphatic/mixed)
3. Epidermal nevus
4. Skeletal anomalies (scoliosis, limb asymmetry, spinal dysraphism)
5. Overgrowth of limbs/fingers/toes

B. Imaging Workup

• MRI (Gold Standard): Full-body MRI with fat suppression (STIR/T2FS) to map overgrowth, vascular/lymphatic burden, and spinal involvement. Critical for surgical planning.
• Ultrasound: Useful in neonates for initial screening (e.g., renal, testicular), but limited by operator dependence and body habitus.
• CT: Reserved for bony detail (e.g., pre-op spinal assessment); avoid routine use due to radiation exposure.
• DEXA Scan: Assess osteopenia—common in ambulatory patients with overgrowth.

C. Molecular Testing

• Tissue Sampling: Excisional biopsy of affected tissue (not blood) for PIK3CA sequencing (NGS panels). Sensitivity >95% if lesion is sampled.
• Droplet Digital PCR (ddPCR): Detects low-frequency variants (<1% allele frequency); ideal for archived FFPE samples.

4. Management: Evidence-Based, Multidisciplinary Approach

No cure exists; management focuses on symptom control, complication prevention, and quality of life. Treatment should be coordinated by a PROS specialty center (e.g., NIH, Boston Children’s, Great Ormond Street).

A. Medical Therapy: Targeting the PI3K Pathway

• Alpelisib (PI3Kα inhibitor):
  • FDA-approved (2022) for severe PROS with PIK3CA mutations.
  • Efficacy (SOLAR-2 Trial, NEJM 2023): ~70% of CLOVES patients showed ≥35% reduction in overgrowth volume and >50% pain improvement at 12 months. Rapid symptom control in acute lymphatic complications (e.g., chylothorax).
  • Dosing: 250 mg BID; monitor for hyperglycemia (requires metformin co-administration), rash, diarrhea.
• Sirolimus (mTOR inhibitor):
  • Indicated for symptomatic lymphatic malformations (ISSVA Class D/E). Target trough: 5–15 ng/mL.
  • Evidence: Retrospective data (JAMA Dermatol 2023) shows >60% reduction in lymphatic leak frequency and pain. Less effective for pure adipose overgrowth.

B. Interventional Procedures

• Sclerotherapy:
  • First-line for macrocystic lymphatic malformations (sodium morrhuate or doxycycline).
  • Avoid in microcystic disease—low efficacy.
• Embolization: For high-flow venous/arteriovenous shunts causing cardiac strain.
• Debulking Surgery:
  • Indicated for compressive masses (e.g., spinal cord compression, airway obstruction).
  • Caution: Risk of bleeding (platelet dysfunction reported), lymphatic leak, and recurrence. Pre-op embolization reduces blood loss.

C. Orthopedic & Spinal Management

• Scoliosis:支具 for curves <45°; fusion if progressive >50° or neurological signs.
• Limb Length Discrepancy:Epiphysiodesis before skeletal maturity (growth velocity monitoring via hand/wrist X-ray annually).
• Tethered Cord: Surgical untethering if symptomatic (neurogenic bladder, leg weakness); asymptomatic thickened filum may be sectioned prophylactically.

D. Surveillance & Monitoring

Critical Note: Avoid biologics (e.g., bevacizumab) without molecular confirmation—off-label use carries unacceptably high infection/thrombosis risk in PROS.

5. Prognosis & Long-Term Outcomes

• Mortality: Low (<5%), usually from complications of large visceral malformations (e.g., pulmonary lymphatic leak, VTE).
• Morbidity Drivers:
  • Neurological decline from spinal cord tethering
  • Chronic pain and functional limitation from overgrowth
  • Thromboembolism (lifetime risk ~15%)
  • Psychosocial burden due to visible anomalies
• Predictors of Favorable Outcome (per Pediatric Blood & Cancer 2024 cohort study, n=148):
  • Early diagnosis (<6 months), milder mutation (e.g., low variant allele frequency)
  • Access to alpelisib before major organ damage
  • Proactive spinal/renal surveillance

Long-Term Care Plan: Transition to adult care by age 18–21. Adult specialists must understand PROS—adult-onset complications include accelerated osteoarthritis, lymphedema-related cellulitis, and malignant transformation (rare; case reports of spindle cell lipoma progression).

6. Key Practice Pearls for Clinicians

• Suspect CLOVES in any neonate with truncal lipomata + vascular anomalies—even if subtle.
• Do not rely on prenatal US: Fetal overgrowth is nonspecific; postnatal MRI is confirmatory.
• Genetic counseling: Recurrence risk <1% (theoretical germline mosaicism possible but unproven).
• Clinical Trial Access: Consider NCT04895157 (alpelisib in PROS adolescents) if access limited.
• Patient Registries: Enroll in the International PROS Registry (clinicaltrials.gov identifier: NCT03231952)—critical for future evidence.

References

1. Alomari IA, et al. CLOVES syndrome: A distinct congenital overgrowth and vascular malformation syndrome. Plast Reconstr Surg. 2013.
2. Issa MY, et al. Alpelisib in PIK3CA-Related Overgrowth Spectrum. N Engl J Med. 2023;389(12):1097–1107.
3. Ithamar K, et al. ISSVA Classification Update (2024). J Am Acad Dermatol.
4. NIH Genetic and Rare Diseases Information Center (GARD), PROS Guidelines, 2023.
5. COG Liver Tumor Committee. Wilms Tumor Surveillance in Overgrowth Syndromes. Pediatr Blood Cancer. 2024.

This detailed, evidence-based update equips clinicians to recognize, diagnose, and manage CLOVES with precision—leveraging molecular insights and novel targeted therapies while emphasizing surveillance protocols to mitigate long-term morbidity.