Hot in the tropics

The approach to clinical conundrums by an expert clinician is revealed through the presentation of an actual patient’s case in an approach typical of a morning report. Similarly to patient care, sequential pieces of information are provided to the clinician, who is unfamiliar with the case. The focus is on the thought processes of both the clinical team caring for the patient and the discussant. The bolded text represents the patient’s case. Each paragraph that follows represents the discussant’s thoughts.
 

A 42-year-old Malaysian construction worker with subjective fevers of 4 days’ duration presented to an emergency department in Singapore. He reported nonproductive cough, chills without rigors, sore throat, and body aches. He denied sick contacts. Past medical history included chronic hepatitis B virus (HBV) infection. The patient was not taking any medications.

For this patient presenting acutely with subjective fevers, nonproductive cough, chills, aches, and lethargy, initial considerations include infection with a common virus (influenza virus, adenovirus, Epstein-Barr virus [EBV]), acute human immunodeficiency virus (HIV) infection, emerging infection (severe acute respiratory syndrome [SARS], Middle Eastern respiratory syndrome coronavirus [MERS-CoV] infection, avian influenza), and tropical infection (dengue, chikungunya). Also possible are bacterial infections (eg, with Salmonella typhi or Rickettsia or Mycoplasma species), parasitic infections (eg, malaria), and noninfectious illnesses (eg, autoimmune diseases, thyroiditis, acute leukemia, environmental exposures).

The patient’s temperature was 38.5°C; blood pressure, 133/73 mm Hg; heart rate, 95 beats per minute; respiratory rate, 18 breaths per minute; and oxygen saturation, 100% on ambient air. On physical examination, he appeared comfortable, and heart, lung, abdomen, skin, and extremities were normal. Laboratory test results included white blood cell (WBC) count, 4400/μL (with normal differential); hemoglobin, 16.1 g/dL; and platelet count, 207,000/μL. Serum chemistries were normal. C-reactive protein (CRP) level was 44.6 mg/L (reference range, 0.2-9.1 mg/L), and procalcitonin level was 0.13 ng/mL (reference range, <0.50 ng/mL). Chest radiograph was normal. Dengue antibodies (immunoglobulin M, immunoglobulin G [IgG]) and dengue NS1 antigen were negative. The patient was discharged with a presumptive diagnosis of viral upper respiratory tract infection.

There is no left shift characteristic of bacterial infection or lymphopenia characteristic of rickettsial disease or acute HIV infection. The serologic testing and the patient’s overall appearance make dengue unlikely. The low procalcitonin supports a nonbacterial cause of illness. CRP elevation may indicate an inflammatory process and is relatively nonspecific.

Myalgias, pharyngitis, and cough improved over several days, but fevers persisted, and a rash developed over the lower abdomen. The patient returned to the emergency department and was admitted. He denied weight loss and night sweats. He had multiple female sexual partners, including commercial sex workers, within the previous 6 months. Temperature was 38.5°C. The posterior oropharynx was slightly erythematous. There was no lymphadenopathy. Firm, mildly erythematous macules were present on the anterior abdominal wall (Figure 1). The rest of the physical examination was normal.

Laboratory testing revealed WBC count, 5800/μL (75% neutrophils, 19% lymphocytes, 3% monocytes, 2% atypical mononuclear cells); hemoglobin, 16.3 g/dL; platelet count, 185,000/μL; sodium, 131 mmol/L; potassium, 3.4 mmol/L; creatinine, 0.9 mg/dL; albumin, 3.2 g/dL; alanine aminotransferase (ALT), 99 U/L; aspartate aminotransferase (AST), 137 U/L; alkaline phosphatase (ALP), 63 U/L; and total bilirubin, 1.9 mg/dL. Prothrombin time was 11.1 seconds; partial thromboplastin time, 36.1 seconds; erythrocyte sedimentation rate, 14 mm/h; and CRP, 62.2 mg/L.

EBV, acute HIV, and cytomegalovirus infections often present with adenopathy, which is absent here. Disseminated gonococcal infection can manifest with fever, body aches, and rash, but his rash and the absence of penile discharge, migratory arthritis, and enthesitis are not characteristic. Mycoplasma infection can present with macules, urticaria, or erythema multiforme. Rickettsia illnesses typically cause vasculitis with progression to petechiae or purpura resulting from endothelial damage. Patients with secondary syphilis may have widespread macular lesions, and the accompanying syphilitic hepatitis often manifests with elevations in ALP instead of ALT and AST. The mild elevation in ALT and AST can occur with many systemic viral infections. Sweet syndrome may manifest with febrile illness and rash, but the acuity of this patient’s illness and the rapid evolution favor infection.

The patient’s fevers (35°-40°C) continued without pattern over the next 3 days. Blood and urine cultures were negative. Polymerase chain reaction (PCR) test of the nasal mucosa was negative for respiratory viruses. PCR blood tests for EBV, HIV-1, and cytomegalovirus were also negative. Antistreptolysin O (ASO) titer was 400 IU/mm (reference range, <200 IU/mm). Antinuclear antibodies were negative, and rheumatoid factor was 12.4 U/mL (reference range, <10.3 U/mL). Computed tomography (CT) of the thorax, abdomen, and pelvis was normal. Results of a biopsy of an anterior abdominal wall skin lesion showed perivascular and periadnexal lymphocytic inflammation. Amoxicillin was started for the treatment of possible group A streptococcal infection.