Can foot drop occur in patients with connective‑tissue diseases such as systemic lupus erythematosus, systemic sclerosis, mixed connective‑tissue disease, Sjögren’s syndrome, polymyositis, or dermatomyositis?

Foot Drop in Connective Tissue Diseases

Yes, foot drop can occur in patients with connective tissue diseases, though it is not a common or characteristic manifestation of these conditions. The mechanism is typically through peripheral neuropathy rather than the primary disease process itself.

Mechanisms of Foot Drop in CTD Patients

Foot drop results from weakness of ankle and foot dorsiflexors, most commonly due to peroneal nerve injury or L5 radiculopathy 1. In connective tissue disease patients, several pathways can lead to this presentation:

Peripheral Neuropathy Pathways

• Vasculitic neuropathy: Small-vessel vasculitis associated with systemic lupus erythematosus, rheumatoid arthritis, and other autoimmune conditions can cause nerve damage 2
• Compressive neuropathy: The most common cause remains peroneal nerve compression at the fibular head, which can occur in any patient regardless of underlying CTD 1, 3
• Radiculopathy: L4/L5 nerve root compression from spinal pathology is another frequent cause that may coincidentally occur in CTD patients 1, 3

Disease-Specific Considerations

Systemic Sclerosis and Overlap Syndromes: While systemic sclerosis primarily causes smooth muscle atrophy, gut wall fibrosis, and microvasculature damage with neural involvement 2, foot drop is not a typical manifestation. However, myopathy can occur in scleroderma overlap syndromes 4.

Polymyositis/Dermatomyositis: These inflammatory myopathies can cause proximal muscle weakness but typically do not present with isolated foot drop as the primary manifestation 2.

Systemic Lupus Erythematosus: SLE is associated with small-vessel disease that can affect peripheral nerves 2, though foot drop as a presenting feature would be unusual.

Mixed Connective Tissue Disease: MCTD patients commonly develop interstitial lung disease (40-80% of cases) and esophageal dysfunction 5, 6, but peripheral neuropathy causing foot drop is not a characteristic feature.

Clinical Approach

Diagnostic Evaluation

When foot drop occurs in a CTD patient, the evaluation should focus on:

• Localization of the lesion: Determine whether the pathology is at the peroneal nerve, sciatic nerve, lumbar plexus, L4/L5 nerve root, or central nervous system 1, 3
• Electrodiagnostic studies: Essential to confirm the site and severity of nerve involvement 1
• Imaging: MRI of the lumbar spine if radiculopathy is suspected, or brain imaging if central causes are considered 7

Treatment Strategy

For compressive peroneal neuropathy: Surgical decompression at the fibular head should be offered to patients with subjectively disturbing foot drop and clinically suspected nerve compression, as this can be performed with minimal risk 1.

For permanent foot drop: Muscle-transfer surgery may benefit selected patients 1.

For spastic foot drop: Evaluate botulinum toxin injections as a treatment option 1.

Ankle-foot orthoses (AFO): Helpful for managing paralyzed foot extensors regardless of etiology 3.

Important Caveats

• Foot drop is not a typical or defining feature of any connective tissue disease mentioned in the question (SLE, systemic sclerosis, MCTD, Sjögren's syndrome, polymyositis, or dermatomyositis)
• When foot drop occurs in CTD patients, investigate common causes (peroneal nerve injury, L5 radiculopathy) rather than assuming it is directly related to the underlying rheumatologic condition 1, 3
• The presence of vasculitis in certain CTDs may predispose to peripheral neuropathy, but this would typically present as part of a broader neuropathic syndrome rather than isolated foot drop 2
• Goals of treatment: Improved mobility, fall prevention, pain reduction, and prevention of abnormal postures 1