A patient in his 70’s presents with diffuse myalgias, weakness, and confusion. He reports he fell out of bed and was found by his wife shortly after. He denies any head or neck injury and denies any headache. He has had a mild cough for two days and notes increasing generalized weakness for 3 to 4 days. His wife adds that the patient seems slower to answer questions than normal. The patient denies any fever or pain other than diffuse muscle aches. He was too weak to get up from the floor when his wife found him so she activated EMS.
PMhx:
- Hypothyroidism
- Prostate Cancer metastatic to the bony pelvis – on prednisone and zytiga therapy.
Exam:
- Vitals- HR 90, BP 130/90, sat 98% on room air, RR 14, Temp 102.5
- General- awake, fatigued appearing
- HEENT- normal
- Neck- supple, no tenderness
- Cardiac- regular, no murmurs, normal distal pulses all extremities
- Resp- clear bilaterally, no cough
- Abdomen- soft, non-tender, no masses
- Extremities- warm, normal passive range of motion, decreased movement due to muscle aches, mild palpable tenderness of major muscle groups of lower extremities, normal compartments.
- Neuro- awake, oriented to self and location, confused regarding year and month. Moves all extremities to command but weak. Sensation normal. Cranial nerves normal. Slight delay in responding to questions.
Differential:
- Sepsis
- UTI / Pyelonephritis
- Pneumonia
- Prostatitis
- Meningitis (not consistent with examination)
- Sub-acute MI
- Dehydration
- Electrolyte abnormality (hyponatremia, hypokalemia)
- Hypothyroidism
- Deconditioning
ED Evaluation:
- The patient receives an IV fluid bolus as labs are performed.
- Fever is treated with acetaminophen
- CXR is normal
- Pertinent labs show WBC normal (7 k/mm3) with a normal differential, creatinine 5 mg/dl with Bun 37 mg/dl.
- Cath urine is dark and tests positive for 3+ blood with 1-2 RBC on microscopy
- CPK is added to labs revealing a level of 149,000 units/L
- Liver enzymes show SGOT 1780 u/l SGPT 346 u/l
Hospital Course:
- Admitted with IV fluid and urine alkalynization. However the patient has minimal urine output with creatinine peaking at 8.5 mg/dl.
- He requires temporary dialysis while inpatient and urine output recovers.
- Viral hepatitis testing is negative.
- Tamiflu (oseltamivir) therapy is initiated inpatient.
- Muscle weakness improves and the patient is discharged to a rehab facility with urine output restored and without further dialysis required.
Diagnosis: Acute Influenza (A) Myositis causing Rhabdomyolysis and Renal Failure
Discussion:
Viral myositis is an acute inflammation of the muscle tissue secondary to a viral infection. Although the exact mechanism is not known, current theories center around direct viral injury to muscle tissue vs. the effect of inflammatory markers on muscle tissue. One of the more severe complications of myosistis is acute rhambdomyolysis. As in our case, muscle breakdown can lead to severely elevated serum levels of creatinine kinase and result in acute renal failure. In cases where urine output is not maintained, temporary dialysis may be required. Other complications of renal failure may occur including hyperkalemia, and cardiac arrhythmias. However, the prognosis is generally good. There are multiple case reports of rhabdomyolysis due to acute influenza infection. Complications commonly include renal injury and in some cases compartment syndrome. Case reports have shown that patients typically improve once the viral inflammatory process subsides, and that renal function is restored even in cases requiring temporary dialysis.
The diagnosis of viral induced rhabdomyolysis is not commonly considered in patients with acute illness. However, the presence of severe muscle weakness with or without fever, should prompt further investigation. Examination for muscle tenderness and assessment of muscle compartments may make the diagnosis more clear. In addition, pigmentation of the urine due to the presence of myoglobin may be present. However, this should not be mistaken for hematuria on a dipstick. If urine microscopy is not available, a high level of suspicion for rhabdomyolysis should be maintained in this clinical setting so as not to confuse the diagnosis with a urinary tract infection when a fever is present.
Influenza and Rhabdomyolysis case reports : Case Reports
For a more in-depth discussion of viral myositis and associated causes, please see:
Up-To-Date: Viral Myositis
Medscape: Infectious Myositis