Patients with chronic mucocutaneous candidiasis (CMC) have persistent or recurrent infections caused by Candida albicans of the mucous membranes, esophagus, skin, and nails. CMC is associated with acquired conditions, including human immunodeficiency virus (HIV), immunosuppression, protracted antibiotic treatment, and diabetes mellitus. CMC is also associated with inherited primary T-cell immunodeficiencies, such as severe combined immunodeficiencies, combined immunodeficiencies, autosomal-dominant hyper-IgE syndrome, and idiopathic CD4 lymphopenia. CMC disease (CMCD) is the presence of CMC in patients with no other defining clinical signs and no other genetic defects. Heterozygous STAT1 missense mutations are seen in patients with CMCD.

Nail involvement is common in patients with CMC. The affected nails often present with thickening, yellow-brown discoloration and subungual hyperkeratosis. Associated paronychia is common. There is often thickening of the soft tissues, resulting in a swollen distal phalanx that is more bulbous than clubbed.

Hyperkeratotic areas secondary to Candida invasion may develop in the proximal and lateral nail folds.