In the ICD-10-CM (International Classification of Diseases, 10th Edition, Clinical Modification) code book, the main term for the diagnosis "Acute frontal sinusitis" is "Sinusitis." When coding for this condition, you would look under the main term "Sinusitis" and then specify the type and laterality if needed. In this case, "Acute frontal sinusitis" falls under the broader category of sinusitis.
