What are the causes of secondary scarring alopecia?

Secondary Scarring Alopecia Causes

Secondary scarring (cicatricial) alopecia results from inflammatory, neoplastic, or physical conditions that primarily damage the dermis and cause follicular destruction as a secondary consequence, unlike primary scarring alopecia where the hair follicle itself is the primary target. 1

Key Distinguishing Feature

• Secondary cicatricial alopecia encompasses diseases that primarily affect the dermis rather than directly targeting the hair follicle, leading to secondary follicular destruction and permanent hair loss through replacement with fibrotic tissue 1
• The hair follicle epithelial stem cells in the bulge region are irreversibly damaged, but this occurs as collateral damage from the primary dermal pathology rather than from direct autoimmune attack on the follicle 2

Major Categories of Secondary Scarring Alopecia

Inflammatory Dermatoses

• Severe bacterial, fungal, or viral infections affecting the scalp dermis can cause secondary follicular destruction 1
• Deep fungal infections (kerion from tinea capitis) represent a common infectious cause that destroys follicles secondarily through intense dermal inflammation 3
• Severe forms of folliculitis that extend beyond the follicle into surrounding dermis may cause secondary scarring 1

Physical Trauma

• Mechanical injury including burns (thermal, chemical, or radiation), lacerations, and surgical scars cause secondary follicular loss through direct tissue destruction 1
• Traction from prolonged tight hairstyling can progress to permanent scarring in advanced cases 1

Neoplastic Conditions

• Primary skin malignancies (basal cell carcinoma, squamous cell carcinoma, cutaneous lymphoma) destroy follicles through tumor infiltration of the dermis 1
• Metastatic tumors to the scalp can cause secondary follicular destruction 1

Infiltrative Disorders

• Sarcoidosis, morphea (localized scleroderma), and other granulomatous or sclerosing conditions primarily affect dermal architecture with secondary follicular loss 1

Clinical Distinction from Primary Scarring Alopecia

• In secondary scarring alopecia, the underlying dermal pathology is usually clinically evident before or concurrent with hair loss, whereas primary scarring alopecia presents with follicular targeting as the dominant feature 1, 4
• Histopathologic examination shows that the inflammatory or pathologic process predominantly involves the reticular dermis rather than being centered on the follicular unit 5

Diagnostic Approach

• Scalp examination must determine whether scarring is present by looking for complete absence of follicular ostia (openings), which distinguishes all cicatricial alopecias from non-scarring types 6
• Skin biopsy is essential when secondary scarring alopecia is suspected to identify the primary dermal pathology and confirm secondary follicular destruction 3
• The clinical context—presence of burns, trauma history, systemic disease, or visible dermal pathology—helps distinguish secondary from primary scarring alopecia 1

Management Implications

• Treatment must address the underlying dermal condition (infection, neoplasm, inflammatory disease) rather than focusing solely on hair restoration, as follicular destruction is permanent once scarring occurs 1
• Early recognition and aggressive treatment of the primary dermal pathology is critical to prevent progression of follicular destruction 7
• Once complete scarring has occurred with total follicular loss, only surgical hair restoration options remain, as the follicular stem cells are irreversibly destroyed 2