Differentials
Infection
SIGNS / SYMPTOMS
Hot, red, swollen, painful extremity.
INVESTIGATIONS
Erythrocyte sedimentation rate, CRP, blood cultures, aspiration of joint, or swab of skin.
Arterial compromise
SIGNS / SYMPTOMS
Colour and temperature changes with cramping and dystonias. Burning pain. Gangrene in extreme cases.
INVESTIGATIONS
Vascular imaging to rule out compression or thrombosis including magnetic resonance angiogram or ultrasound (Doppler).
Bone pathology
SIGNS / SYMPTOMS
Swelling, red, hot extremity with pain on movement.
Fracture malunion, stress responses including fractures, osteomyelitis (including sterile forms), and tumours should be considered.
INVESTIGATIONS
X-ray, CT, MRI, or radionuclide bone scan showing cortical injury or oedema.
Peripheral neuropathy due to a metabolic cause
SIGNS / SYMPTOMS
Underlying diabetes mellitus, renal failure, alcoholism, malnutrition (low vitamin B12 or folic acid); hereditary sensorimotor neuropathies; also consider hereditary or acquired erythromelalgia.
Symptoms of pain, burning, and hyperalgesia are symmetrical and tend to begin in the distal lower extremities and affect the upper extremities later.
There is usually no history of trauma, and most peripheral neuropathies progress gradually.
If large fibres are involved there is a loss of reflexes, weakness, and vibratory and proprioceptive deficits.
INVESTIGATIONS
Nerve conduction studies and electromyogram reveal abnormal action potentials detected symmetrically.
Elevated urea and creatinine with renal failure.
Elevated fasting blood glucose >125 mg/dL with diabetes mellitus.
Focal or entrapment neuropathies
SIGNS / SYMPTOMS
Symptoms and signs are confined to the distribution of the affected nerve (e.g., carpal tunnel, cubital tunnel, or thoracic outlet syndrome).
No history of trauma.
INVESTIGATIONS
Usually a clinical diagnosis.
Nerve conduction abnormalities confined to the affected nerve and its innervated musculature.
MRI reveals a high-intensity signal at point of entrapment. Only useful for large nerves (e.g., ulnar).
Deep vein thrombosis
SIGNS / SYMPTOMS
Swelling, pain, and discoloration of the affected extremity. Burning, electrical, or shooting pains are uncommon.
INVESTIGATIONS
Compression ultrasonography shows non-compressibility of vascular lumen on gentle pressure.
Impedance plethysmography may reveal a reduction in venous emptying and consequent slower rise in impedance. Result is operator-dependent.
Thrombophlebitis
SIGNS / SYMPTOMS
Focal pain, swelling, tenderness, erythema, and a palpable cord in the affected vein.
INVESTIGATIONS
Usually a clinical diagnosis.
Compression ultrasonography may be used to detect spread of inflammation to deep veins.
Lymphoedema
SIGNS / SYMPTOMS
Often secondary to surgery, radiation, or infection. Onset is insidious; oedema is non-pitting; pain is usually aching in nature.
Idiopathic oedema is a common cause of oedema in women.
Incompetent perforating veins also can cause leg oedema.
INVESTIGATIONS
Lymphoscintigraphy outlines the anatomy of the lymphatic system and identifies areas of obstruction to flow.
Gout
SIGNS / SYMPTOMS
Affects joints, most commonly the big toe.
Sudden onset; may have history of symptoms or gouty tophi visible in long-standing hyperuricaemia.
INVESTIGATIONS
Usually a clinical diagnosis.
Synovial fluid aspirate shows monosodium urate crystals.
Pseudogout
SIGNS / SYMPTOMS
Can present as acute mono-articular arthritis or a poly-articular symmetrical arthritis similar to rheumatoid arthritis. Typically affects shoulders and wrists.
INVESTIGATIONS
Synovial fluid aspirate shows calcium pyrophosphate crystals.
Scleroderma
SIGNS / SYMPTOMS
Accompanied by other features of scleroderma: skin tightness, calcinosis, itching, Raynaud's syndrome, or elevated blood pressure.
INVESTIGATIONS
Presence of antinuclear antibodies on serological testing.
Tenosynovitis due to spondyloarthropathy (e.g., ankylosing spondylitis)
SIGNS / SYMPTOMS
Pain to palpation at site of tendon insertion; common sites include Achilles tendon and insertion of plantar fascia on to calcaneus.
Associated features of a spondyloarthropathy (e.g., morning stiffness, fatigue, low-grade fever, low back pain, or extra-articular manifestations).
INVESTIGATIONS
Diagnosed on clinical criteria and radiographic findings of bony erosion and periosteal new bone formation.
HLA-B27 antigen positive in majority of cases but not usually tested.
Psychological or (neuro)psychiatric diagnoses (e.g., PTSD, personality disorders including borderline personality disorder, somatic symptom disorders, body image identity disorder)
SIGNS / SYMPTOMS
Important to consider when taking history.
Difficult, chaotic, or abusive childhood experiences can affect personality development.
Nightmares, flashbacks, and overactive sympathetic nervous systems might suggest PTSD.
Body image identity disorder develops around puberty and is not usually associated with significant pain.
INVESTIGATIONS
Consultation with an appropriate healthcare professional is important when considering these diagnoses.
Compartment syndrome of extremities
SIGNS / SYMPTOMS
Progressive pain in appropriate clinical scenario out of proportion to the injury, often presenting with tense, swollen tissue (stiff, 'wood-like') and pain with passive movement. Compartment syndrome is often a surgical emergency and develops soon after trauma, fracture, surgery, ischaemia-reperfusion injury, coagulopathy, peripheral traumas with associated pathophysiology of swelling (bites, envenomation, IV drug use, extravasation of IV fluids), and prolonged compression of tissue. Paraesthesias may indicate ischaemic nerve injury.
INVESTIGATIONS
Surgical consultation, with consideration of direct compartment pressure measurement in appropriate clinical context.
Raynaud's phenomenon
SIGNS / SYMPTOMS
Generally affecting most distal aspect of circulatory beds, such as digits, ears, nipples, and nose. Presentation tends to be of quick onset in setting of precipitating factors (low temperature, shift from lower to higher temperature) with evidence of clearly demarcated skin pallor in area of cold with symptoms of digital ischaemia (paraesthesia, pain, numbness, impaired fine motor skills), and in some patients evidence of livedo reticularis.
INVESTIGATIONS
No differentiating tests; careful clinical history of symptoms and triggering events is utilised in diagnosis.
Erythromelalgia
SIGNS / SYMPTOMS
Distal extremities (often bilateral) become red, hot and painful (often described as burning) with swelling. Episodes last minutes to hours, often triggered by increase in ambient heat or exercise. Number of episodes can vary between patients.
INVESTIGATIONS
As erythromelalgia can be associated with myeloproliferative disorders, a complete blood count is recommended, but is not diagnostic.
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