How common is calf swelling in patients with Neurofibromatosis Type 1 (NF1)?

Calf Swelling in Neurofibromatosis Type 1 (NF1)

Calf swelling is a rare manifestation of Neurofibromatosis Type 1, with only isolated case reports documenting ankle swelling due to diffuse neurofibromas. 1 While plexiform neurofibromas can occur in various body locations, specific presentations in the calf region are not commonly reported in the medical literature.

Common Manifestations of NF1

NF1 typically presents with:

• Cutaneous manifestations:

  • Café-au-lait macules (light brown patches)
  • Cutaneous neurofibromas (present in >99% of adults with NF1) 2
  • These begin to appear during puberty and increase in number with age

• Plexiform neurofibromas:

  • Complex nerve sheath tumors following multiple nerve branches
  • May demonstrate rapid growth during childhood
  • Have risk for malignant transformation 3
  • Can cause functional and neurologic deficits

• Skeletal manifestations:

  • Scoliosis (dystrophic and nondystrophic forms)
  • Long bone dysplasia/pseudarthrosis (particularly affecting the tibia)
  • Sphenoid wing dysplasia
  • Decreased bone mineral density and osteoporosis 3, 2

Vascular Manifestations and Swelling in NF1

While calf swelling specifically is rare, NF1 can cause vascular abnormalities that might present with swelling:

• NF1-associated vasculopathy affects small, medium, and large vessels (primarily arteries) 3
• Types of vascular abnormalities include:
  • Arterial stenosis
  • Aneurysms
  • Arteriovenous malformations
  • Vessel compression by neurofibromas 3

Documented Cases of Lower Extremity Swelling

The most recent evidence specifically addressing ankle swelling in NF1 comes from a 2022 case report that documented two patients with NF1 presenting with solitary swelling in the ankles, which were proven to be diffuse type neurofibromas 1. This report specifically noted that such presentations had not been previously documented in the literature.

Clinical Implications

When evaluating calf swelling in NF1 patients:

• Consider the possibility of a diffuse neurofibroma
• Evaluate for plexiform neurofibromas that may be compressing vascular structures
• Assess for NF1-associated vasculopathy
• Rule out common causes of calf swelling unrelated to NF1

Diagnostic Approach

For NF1 patients presenting with calf swelling:

• MRI imaging is the preferred modality to evaluate for neurofibromas
• Vascular studies may be indicated to assess for vasculopathy
• Biopsy may be necessary to confirm neurofibroma and rule out malignant transformation

Treatment Considerations

Management depends on the underlying cause:

• Surgical intervention may be considered for symptomatic neurofibromas
• Physical therapy and compression garments for symptomatic relief
• Monitor for pain, which could indicate malignant transformation 3, 2

In conclusion, while NF1 commonly presents with multiple cutaneous manifestations, isolated calf swelling is an uncommon presentation with limited documentation in the medical literature.