History of present illness: The patient is a 70 year old female who is normally in good health. She complains of left lower extremity weakness, dyspnea and low back pain which began 2 days ago. The patient began taking prednisone 2 to 3 days ago after being diagnosed with "poison ivy dermatitis" on her left arm.
Review of systems: No malaise, fever, diaphoresis, headache, vision or hearing problems, chest pain, nausea, vomiting, diarrhea. Mildly "upset stomach".
Medications: Prednisone in tapering doses since 2 to 3 days ago.
Allergies: None.
Past Medical History: No prior hospitalizations. No other illnesses.
Past Surgical History: Left breast biopsy and ankle fracture ( both many years ago)
Social history: Denies tobacco use, drug abuse or alcohol abuse.
Family history: Diabetes. No family history of cancer, hypertension or heart disease.
Physical examination: Vital signs: temperature 35.8, pulse 130, respirations 22, blood pressure 168/80.
General: Alert and oriented x 3 in no distress. No dehydration.
Skin: Vesicular rash on left shoulder with mild surrounding erythema. No other rash.
HEENT: Normocephalic, atraumatic; pupils equal, round and reactive to light; extra ocular muscles intact; conjunctiva not injected; tympanic membranes normal; throat normal without erythema or exudate.
Neck: No meningeal signs; no cervical tenderness; no jugular venous distention; no bruits.
Heart: Regular tachycardic rhythm. No murmurs, rubs or gallops.
Lungs: Diminished breath sounds at the bases, otherwise clear.
Abdomen: Normal bowel sounds; soft; nontender; no masses rebound or guarding; no hernias.
Back: No lesions. No bony tenderness or step-off. No tenderness of paraspinal area.
Extremities: No tenderness, rash as noted above. Pulses are normal and equal.
Neurologic: Normal mental status. Cranial nerves intact. Motor strength intact except for decreased left knee and ankle reflexes and weakness of left hip flexion and left knee extension. Normal sensory exam except for mild numbness of the left thigh. Cerebellar exam is normal.
Laboratory: EKG: Sinus tacycardia at 132 with no acute changes.
Chest xray: No active disease.
WBC; 18.4, hemoglobin: 16.5, hematocrit: 50.4, platelets: 334.
Chem 20: unremarkable.
pH: 7.46, pCO2 29, pO2 81 on room air.
Pulmonary ventilation/perfusion scan: Low probability for pulmonary embolism.
Disposition: The patient was admitted for further evaluation. Her neurologic exam returned to normal after one week of treatment.
What is your diagnosis?