Myositis in a Child with Murine Typhus
A previously healthy 12-year-old boy was admitted to Driscoll Children’s Hospital in Corpus Christi, TX, USA, with a 9 day history of fever, and 7 day history of pain and weakness in the lower extremities. Three days prior to admission, he was seen by a nurse practitioner and diagnosed with otitis media and pharyngitis. He received intramuscular penicillin and was prescribed cefixime for 3 days without improvement. He progressed and he became unable to walk without assistance. He had no gastrointestinal, respiratory or genitourinary complaints. On admission, his temperature was 36.8°C and the physical examination was significant for antalgic, broad-based gait and tender gastrocnemius – soleus muscles. Biceps, quadriceps and psoas muscle strength was graded at 3/5. Sensation and deep tendon reflexes were normal with absent Romberg’s and Babinski’s sign. The white blood cell count was 8300 cells per cubic mm with 60% neutrophils and 40% lymphocytes, hemoglobin was 13.5 g/dL, and the platelet count was 172,000 cells per cubic mm. His CRP was 1.5 mg/dL. The ESR and urine analysis were normal. Creatinine phosphokinase (CPK) was elevated at 2394 μ/L, aspartate aminotransferase (AST) was 222 μ/L and, alanine aminotransferase (ALT) was 143 μ/L.\nA diagnosis of myositis was made and the patient was given analgesics and oral prednisone as dermatomyositis and polymyositis were amongst the differential diagnosis. Rhabdomyolysis was considered in the differential diagnosis and the patient was started on one and a half maintenance intravenous fluids. He did not have dark urine or hyperkalemia or myoglobinuria or renal failure. Our patient’s clinical course was not severe and did not develop the complications usually associated with rhabdomyolysis. On day 2 of his hospital stay, he was able to stand up with support and CPK levels came down to 1713 U/L. Cerebrospinal fluid analysis showed a protein concentration of 62 mg/dL and white blood cell count of 4. Electromyography and nerve conduction studies did not show evidence of Guillain Barre Syndrome. A multiplex respiratory viral PCR was positive for rhinovirus and negative for Influenza A and B, parainfluenza, metapneumovirus and adenovirus. Lyme disease serology and monospot for Epstein Barr Virus were reported negative. Arboviral titers for West Nile virus was negative and so was the Rocky Mountain spotted fever titers. On the day 3 of his hospitalization, his upper extremity strength significantly improved to 5/5 and lower extremity to 4/5. Hence he was able to sit up and walk down the hallway without support. Rickettsia typhi IgM was elevated at 512 and IgG at 1024. Serum was evaluated by use of an indirect immunofluorescence antibody (IFA) test kit for immunoglobulin G (IgG) to Rickettsia typhi and Rickettsia rickettsii (Focus Diagnostics, Cypress, CA, USA). Reciprocal titers >64 were considered positive. CPK, ALT and AST levels were noted to have a downward trend. Blood and cerebrospinal fluid cultures showed no growth. The complete recovery of the patient took about 48 hours which included 100 mg of doxycycline given twice daily by mouth. He was discharged home on doxycycline to complete a 10 day course and prednisone was discontinued.