How not to miss a blastomycosis diagnosis in children
May 14 2018
Blastomycosis is a life-threatening disease endemic to regions of North America with sporadic cases in India, Africa, and South America. Symptoms at presentation may appear nonspecific and 'viral' (fever, fatigue, cough), which delays diagnosis and increases the risk of mortality. Disease may be pulmonary or extra-pulmonary.
The first large scale (N=114) paediatric study on balastomycosis has been published by Dr Frost and her team in Wisconsin.
Risk factors included: living near water (61% of cases); owning a dog (33%); having asthma (25%); recent hiking, camping or fishing trips (50%).
Common nonspecific presenting symptoms of both forms included: cough (82%); fever (79%); fatigue (68%); chest pain (65%); poor oral intake (58%).
Extrapulmonary disease had some additional key clinical symptoms and signs: bone and joint pain (71%); skin lesions (50%); fracture (17%); abnormal neurology (13%).
Normal inflammatory markers did not rule out disease: the median highest CRP was 10.5 mg/dL and in extrapulmonary disease it was only 2.2 mg/dL. A raised white blood cell count was useful only in the pulmonary group with a median of 17.6 per 1000/uL and highest ESR was a useful indicator in both groups with a median of 60 mm/h. Performing a CXR was also helpful: infiltrates were seen in 92% of the pulmonary group and 50% of the extrapulmonary group.
A delay in diagnosis was common, taking an average of 19 days from symptom onset, and in extrapulmonary disease this was 45 days. The majority of patients received the recommended itraconazole (81%); however, fluconazole (14%), voriconazole (10%) and ketoconazole (5%) were also used. Amphotericin B was given to 39 patients (34%) either alone or in combination with an azole. 5 children with pulmonary blastomycosis died from respiratory failure despite receiving amphotericin B.
The same group also recently published a multiplexed SNP assay panel for distinguishing between different types of Blastomyces that cost less than the currently used microsatellite assay.
What can I do?
Consider blastomycosis in children presenting with nonspecific viral symptoms who have recently been camping or fishing, even in cases where CXR and inflammatory markers are normal.
Look for characteristic skin lesions and bone/joint pain in suspected extrapulmonary blastomycosis.
Look for lung infiltrates and chest pain in suspected pulmonary blastomycosis.
Be aware that Blastomyces may only be handled in a biosafety level 3 laboratory
Blastomyces skin lesion (photo from AAFP.org)