['Mannose-binding lectin (MBL) is a circulating collectin that is part of the innate immune response. We explored the serum levels of MBL in persons with different forms of coccidioidomycosis.', 'Serum MBL was measured by ELISA from samples obtained from healthy donors with immunity to Coccidioides, and those with various forms of active coccidioidomycosis. Blood cell specimens from a subgroup of subjects with active coccidioidomycosis were examined for single nucleotide polymorphisms of the MBL gene and promoter regions.', 'The control group comprised 29 healthy immune subjects. Patient groups with active coccidioidomycosis consisted of 20 patients with symptomatic primary pulmonary coccidioidomycosis, 26 with non-meningeal disseminated coccidioidomycosis, and nine with coccidioidal meningitis. The group with active coccidioidomycosis was significantly older and more likely to be male than the control group (for both, P < 0.001). The mean +/- SEM level of serum MBL in the healthy controls was 169.4 +/- 28.6 ng/ml, significantly higher than the 79.2 +/- 10.9 ng/ml for all active groups (P < 0.001). Moreover, the active coccidioidomycosis group was significantly more likely to have serum MBL level <or=70 ng/ml compared to the control group (P = 0.001). Genetic analysis in 27 subjects with active coccidioidomycosis revealed marked variation based on race and ethnicity. Among a subgroup of 10 white, non-hispanic men with active coccidioidomycosis, there was a significant association between the H and P haplotypes and MBL levels <or=70 ng/ml (P < 0.036 and P < 0.035, respectively).'] Are mannose-binding lectin serum levels low in persons with clinically active coccidioidomycosis?