G-CSF-Associated Superficial and Deep Neutrophilic Folliculitis of the Scalp with Folliculitis Decalvans-Like Features.

Granulocyte colony-stimulating factor (G-CSF) is known to induce several cutaneous neutrophilic reactions, including Sweet syndrome-like eruptions, neutrophilic panniculitis, neutrophilic eccrine hidradenitis, and sterile folliculitis. We report the case of a male patient with an unclassified malformative syndrome and chronic neutropenia who developed acute painful suppurative nodular scalp lesions while receiving long-term G-CSF therapy and during a period of marked neutrophilia. Histopathological examination showed superficial and deep suppurative neutrophilic folliculitis with follicular abscess formation, follicular epithelial destruction, focal perifollicular fibrosis, neutrophilic epidermotropism, and sparse Gram-positive cocci within deep follicular abscesses. Because the clinical course was acute and a chronic relapsing course, tufted hairs/polytrichia, and unequivocal irreversible cicatricial alopecia were not documented, we do not regard the findings as sufficient for a definitive diagnosis of classic folliculitis decalvans. Rather, the case is best interpreted as G-CSF-associated destructive neutrophilic folliculitis of the scalp with folliculitis decalvans-like features. This case broadens the spectrum of G-CSF-associated follicular reactions and supports the possibility that G-CSF-driven neutrophilia may facilitate severe folliculocentric neutrophilic inflammation, particularly in the setting of bacterial colonization or infection and altered host immunity.