Case Presentation: A healthy 21-year-old female presented to the children’s hospital with a one-week history of worsening bilateral calf pain, unilateral right lower extremity (RLE) swelling, and cool extremities. Symptoms began after a 12-hour work shift, accompanied by a diffuse erythematous papular rash and intermittent asymmetric joint pain. Her medical history included streptococcal pharyngitis treated with amoxicillin two weeks prior, a flu vaccine administered one day before symptom onset, and recent travel to the Dominican Republic. Initial outpatient diagnosis of muscular pain led to ketorolac treatment. She subsequently developed immobility due to pain, persistent RLE swelling, and cold extremities, prompting further evaluation. On admission, the patient exhibited RLE swelling, tenderness, decreased sensation below the right ankle, and posterior tibialis and dorsalis pedis pulses that were non-palpable but audible via Doppler. Labs revealed no leukocytosis, mildly elevated inflammatory markers (CRP 1.4, ESR 9), and CK of 107. Imaging ruled out deep vein thrombosis (DVT) and acute arterial thrombus. Infectious workup was negative for sexually transmitted infections, Lyme disease, and active streptococcal infection, though antistreptolysin O antibody was elevated. Autoimmune testing revealed ANA (1:320) and RNP (2.4). MRI showed fascial enhancement consistent with fasciitis without myositis. The patient improved with supportive care, mobilized with a walker, and was discharged with a diagnosis of unilateral fasciitis of unknown etiology and outpatient rheumatology follow-up.
Discussion: This case highlights the diagnostic complexity of unilateral leg pain and swelling, necessitating a broad differential diagnosis. Life-threatening conditions, including acute limb ischemia and DVT, were excluded early through imaging. The absence of myositis, rhabdomyolysis, or significant infectious symptoms further narrowed the differential. Though post-vaccine vasculitis and rare neurologic complications such as Guillain-Barré syndrome were considered, imaging and clinical findings were inconsistent. Mildly elevated inflammatory markers and positive ANA and RNP raised suspicion for underlying rheumatologic disease, warranting further investigation. The etiology of fasciitis and associated weakness remains unclear, emphasizing the need for continued outpatient evaluation.
Conclusions: Unilateral leg swelling requires a systematic diagnostic approach to identify potentially life-threatening conditions while exploring less common etiologies. Hospitalists should remain vigilant in recognizing diverse presentations and tailoring workups to ensure comprehensive care.
