Dissecting Cellulitis of the Scalp

Dissecting cellulitis of the scalp (also called perifolliculitis capitis abscedens et suffodiens or Hoffmann disease) is a rare, chronic inflammatory disease of the scalp. It causes painful lumps (nodules) and pockets of pus (abscesses) that are connected beneath the skin by tunnels (sinus tracts). Over time, this ongoing inflammation destroys hair follicles and leads to permanent hair loss with scarring (scarring or cicatricial alopecia).

Despite the word "cellulitis" in its name, it is not an infection in the usual sense. It belongs to a group of conditions called the follicular occlusion tetrad — together with hidradenitis suppurativa, severe (conglobate) acne, and pilonidal disease — in which hair follicles become blocked, rupture, and trigger intense inflammation.

• Sex: The condition affects men far more often than women — roughly 9 out of 10 patients are male
• Age: It usually begins in early adulthood, most commonly between 20 and 40 years of age
• Skin type and ancestry: It is seen most often in people of African descent, though it can occur in any ethnic group
• Associated conditions: Many patients also have, or later develop, other follicular occlusion disorders — particularly hidradenitis suppurativa and severe acne
• Overall it is considered rare, but it is likely underrecognized because it can be mistaken for a simple infection

The condition typically develops gradually and follows a long, relapsing course.

• Painful nodules and abscesses: Firm or fluctuant (fluid-filled) lumps appear, most often on the crown (vertex) and back (occiput) of the scalp
• Interconnecting sinus tracts: The lumps become linked by tunnels under the skin. A characteristic sign is that pressing on one area causes pus to emerge from a separate opening some distance away — the scalp feels soft and "boggy"
• Discharge: A recurrent flow of pus or blood-tinged fluid, sometimes with an odour
• Hair loss: As the follicles are progressively destroyed, patches of permanent, scarring baldness develop
• Chronic, relapsing course: Symptoms tend to flare and settle repeatedly over months and years

Psychosocial impact: Because it affects a highly visible area and can cause disfigurement, odour, and permanent hair loss, dissecting cellulitis often has a substantial emotional toll. Patients frequently experience embarrassment, low self-esteem, anxiety, and social withdrawal. This burden deserves attention alongside the physical treatment.

The exact cause is not fully understood, but the process begins with blockage of the hair follicles. A build-up of keratin (the protein that makes up hair and the outer skin) plugs and widens the follicle until it ruptures. The follicle contents spilling into the surrounding skin provoke an intense inflammatory reaction, forming the nodules, abscesses, and tunnels.

• Follicular occlusion, not primary infection, is the central event — bacteria found in the lesions are generally secondary and colonize already-damaged tissue
• Immune dysregulation: An overactive inflammatory response (involving immune messengers such as TNF-alpha and certain interleukins) sustains the disease and is the reason modern targeted treatments can help
• Shared mechanism with hidradenitis suppurativa: The two conditions are increasingly seen as closely related, which is why they often occur together and respond to similar treatments
• Contributing factors may include a genetic predisposition and, as in hidradenitis suppurativa, smoking and obesity

Diagnosis is usually clinical — based on the typical appearance and history.

• Clinical examination: The combination of boggy scalp nodules, interconnecting sinus tracts, discharge, and scarring hair loss is highly suggestive
• Dermoscopy (trichoscopy): Examination with a magnifying device can support the diagnosis, showing features such as yellowish structureless areas, dystrophic hairs, and follicular changes
• Swabs and cultures: Taken mainly to rule out a primary infection and to identify any secondary bacteria
• Skin biopsy: Occasionally performed to confirm the diagnosis or exclude other conditions
• What else it might be: A fungal scalp infection (tinea capitis/kerion), folliculitis decalvans, acne keloidalis nuchae, or an ordinary bacterial abscess can look similar and must be distinguished

There is no guaranteed cure, and the disease tends to return when treatment stops, so the goal is long-term control and prevention of further scarring. Treatment is often combined and tailored to severity.

• Oral isotretinoin: A vitamin-A–derived retinoid taken by mouth; the most established treatment, often producing marked improvement, though relapse after stopping is common
• Antibiotics: Prolonged courses (particularly tetracyclines such as doxycycline, or a clindamycin–rifampicin combination) are used for their anti-inflammatory effect as much as for infection
• Corticosteroids: Injected directly into stubborn nodules, or a short oral course to calm a severe flare
• Biologic therapies: Injectable drugs that block specific inflammatory signals (such as TNF-alpha inhibitors like adalimumab) are increasingly used for moderate-to-severe or treatment-resistant disease
• Procedures: Draining large abscesses, laser hair removal to reduce the follicular load, photodynamic therapy, and — for severe, unresponsive cases — surgical removal of affected scalp
• Self-care: Gentle antiseptic scalp hygiene, and (as in hidradenitis suppurativa) stopping smoking and maintaining a healthy weight may help

• Dissecting cellulitis is a chronic inflammatory condition, not a contagious infection, and it is not cancer
• Early treatment matters: because the hair loss it causes is permanent, starting treatment sooner can help limit lasting scarring
• The condition is often linked to hidradenitis suppurativa and severe acne — tell your doctor if you have these
• No single treatment works for everyone, and relapses are common — ongoing follow-up and combined treatment give the best results
• When to seek medical attention: See a dermatologist for any recurrent painful scalp lumps, discharge, or spreading hair loss. Seek review promptly if a long-standing area changes in appearance, hardens, or develops a non-healing sore
• The emotional impact is real — do not hesitate to raise it with your doctor, and consider psychological support if the condition affects your wellbeing

Dissecting cellulitis of the scalp (DCS), synonymous with perifolliculitis capitis abscedens et suffodiens (PCAS) and historically termed Hoffmann disease, is a rare primary neutrophilic cicatricial alopecia.

• Sex: Strong male predominance — approximately 95% of reported patients are male (356/375 in a large systematic review; Masson et al., 2023)
• Age: Onset most often in the second to fourth decades (peak 20–40 years), though a wide age range (from infancy to the eighth decade) is documented
• Ethnicity: Historically described most frequently in individuals of African descent, but reported across all skin phototypes and populations
• Associated conditions: Frequent coexistence with other follicular occlusion disorders — acne (~17.5%) and hidradenitis suppurativa (HS, ~8.6%) in pooled data
• Classification: True incidence and prevalence are unknown; the disease is rare and likely underreported and misdiagnosed as bacterial infection

Etiology

DCS is a disorder of follicular occlusion rather than a primary infectious process. The initiating event is thought to be follicular hyperkeratosis and infundibular plugging, leading to follicular dilatation, retention of keratinous debris, and eventual follicular rupture. Extrusion of follicular contents (keratin, sebum, microbial antigens) into the dermis triggers a brisk neutrophilic and subsequently granulomatous inflammatory response.

Bacteria (commonly Staphylococcus aureus, coagulase-negative staphylococci, anaerobes) are generally regarded as secondary colonizers of already-damaged tissue; they may perpetuate inflammation but are not considered the primary driver, which explains the frequently disappointing response to antibiotics alone.

Pathophysiology

• Follicular occlusion tetrad: DCS is one of the four follicular occlusion disorders alongside HS, acne conglobata, and pilonidal disease, which share the pathomechanism of follicular plugging, rupture, and dysregulated inflammation
• Immune dysregulation: An aberrant innate and adaptive immune response is central. Elevated activity within the TNF-α, IL-1, IL-17, and IL-23/Th17 axes has been implicated, mirroring findings in HS and providing the rationale for biologic therapy
• Relationship with HS: Accumulating clinical and pathogenic evidence supports viewing DCS and HS as anatomical/phenotypic variants along a single follicular-occlusion spectrum (Valtellini et al., 2026), with important implications for classification and management
• Contributing factors: A genetic predisposition is suspected (rare familial cases; associations with keratin-pathway and connexin disorders such as keratitis–ichthyosis–deafness syndrome are reported). Metabolic and lifestyle factors relevant to HS — smoking, obesity — are commonly cited cofactors

Primary features

• Onset with follicular papules/pustules progressing to firm and fluctuant inflammatory nodules and abscesses
• Interconnecting sinus tracts: hallmark feature; digital pressure over one nodule expresses purulent material from a distant sinus opening, producing the characteristic "boggy" scalp
• Predilection sites: vertex and occiput most commonly, though any part of the scalp may be involved
• Recurrent purulent or serosanguineous discharge, sometimes malodorous
• Progressive scarring (cicatricial) alopecia as follicular units are destroyed

Disease course

Chronic and relapsing, with alternating flares and partial remissions over years. Untreated or inadequately treated disease progresses to extensive, permanent scarring alopecia.

Associated conditions and complications

• Follicular occlusion tetrad components (HS, acne conglobata, pilonidal disease)
• Musculoskeletal/inflammatory associations: SAPHO syndrome and seronegative (spondylo)arthropathy have been reported
• Keratitis–ichthyosis–deafness (KID) syndrome and other rare genodermatoses
• Squamous cell carcinoma: a rare but recognized long-term complication arising in chronically inflamed, scarred lesions — warrants vigilance and biopsy of atypical or non-healing areas
• Keloid formation and, uncommonly, secondary deep infection

Clinical diagnosis

DCS is primarily a clinical diagnosis based on the constellation of boggy scalp nodules, interconnecting sinus tracts, purulent discharge, and scarring alopecia, typically in a young adult man. A history of HS or acne conglobata supports the diagnosis.

Trichoscopy

Dermoscopic (trichoscopic) features support the diagnosis and help stage activity:

• Active/inflammatory: follicular pustules, yellow crusts, keratotic plugs, and yellowish structureless (amorphous) areas over erythematous, boggy plaques; 3D yellow dots overlying dystrophic hairs; black dots and broken/dystrophic hairs
• Chronic/scarring: pinpoint white dots, whitish structureless areas, and loss of follicular openings reflecting fibrosis

Findings vary with lesion age:

• Early: follicular hyperkeratosis/occlusion with perifollicular and perivascular neutrophilic infiltrate
• Established: dermal and subcutaneous abscesses, sinus tracts lined by granulation or squamous epithelium, mixed infiltrate (neutrophils, lymphocytes, plasma cells, histiocytes) with a granulomatous component
• Late: extensive dermal fibrosis and destruction of follicular units (cicatricial alopecia)

Imaging

High-resolution ultrasound and, in selected refractory or extensive cases, MRI can delineate the depth and extent of sinus tracts and fluid collections and guide surgical planning.

Microbiology

Swabs/cultures are chiefly to exclude a primary infection and to characterize secondary colonization; growth of S. aureus does not equate to a primary pyogenic process.

• Tinea capitis / kerion: fungal infection; KOH microscopy and fungal culture distinguish it
• Folliculitis decalvans: tufted folliculitis with prominent pustules and crusting, typically S. aureus-driven; lacks the deep interconnecting sinus tracts
• Acne keloidalis nuchae: keloidal papules/plaques at the occiput/nape
• Bacterial abscess/carbuncle: acute, localized, culture-positive, responds to antibiotics
• Hidradenitis suppurativa of the scalp margin and other neutrophilic scarring alopecias

No RCT-based guidelines exist; recommendations derive largely from case series, cohorts, and systematic reviews. Treatment is stratified by severity and refractoriness, frequently combined, and generally long-term because relapse after discontinuation is common.

First-line

• Oral isotretinoin — the best-established systemic therapy. Reported dosing typically 0.3–1 mg/kg/day continued for several months (often 1–12+ months); pooled response ~90%, but relapse commonly follows cessation. Prolonged, sometimes low-dose maintenance is often required
• Systemic antibiotics for anti-inflammatory effect — tetracyclines are most used (e.g., doxycycline 100–200 mg/day for ≥3 months); the clindamycin–rifampicin combination (as in HS) is a common alternative. Improvement is frequent but relapse after stopping is typical
• Intralesional corticosteroids for individual recalcitrant nodules; a short course of oral corticosteroid (prednisone ~0.5–1 mg/kg with taper) can abort a severe acute flare

Second-line and refractory (biologics and small molecules)

• TNF-α inhibitors: best-evidenced biologic class. Adalimumab (HS-type dosing, e.g., 40–80 mg every 1–2 weeks; reported response ~94%) and infliximab (5 mg/kg every 4–8 weeks; ~86%) improve nodule/abscess counts, pain, and quality of life in conventional-therapy failures (Alzahrani et al., 2023; Masson et al., 2023)
• IL-17 and IL-23 inhibitors (e.g., secukinumab; guselkumab, risankizumab, tildrakizumab) show promise in recalcitrant disease in case-based data (Heidari et al., 2025)
• Small-molecule inhibitors: JAK inhibitors (upadacitinib, baricitinib) and the PDE4 inhibitor apremilast have shown benefit in reports; certolizumab pegol may be considered where pregnancy is a factor
• Evidence for reversal of established scarring and durable hair regrowth remains limited for all immunomodulators

Procedural and surgical

• Photodynamic therapy (5-aminolevulinic acid, 3–7 sessions): improvement in the majority, though recurrences are frequent
• Laser depilation to reduce follicular load: long-pulsed Nd:YAG (favored in skin of color), diode, and ablative Er:YAG lasers have all shown benefit in small series
• External-beam radiotherapy / X-ray epilation: high remission rates but reserved due to morbidity
• Incision and drainage for fluctuant abscesses (symptomatic relief)
• Wide surgical excision ± split-thickness skin grafting for extensive refractory disease — highest durable remission rates but significant morbidity

Adjunctive measures

Antiseptic scalp hygiene; smoking cessation and weight optimization (extrapolated from HS); analgesia; and screening/management of associated follicular occlusion and inflammatory-arthritic comorbidities. Psychological support should be offered given the marked quality-of-life impact.

Monitoring

Isotretinoin: lipids, hepatic transaminases, and pregnancy prevention per standard retinoid protocols. Biologics: infection screening (including tuberculosis/hepatitis) before initiation and standard on-treatment surveillance. Track nodule/abscess counts, pain scores, and validated quality-of-life measures (e.g., DLQI) to gauge response.

DCS is a chronic, relapsing, and often recalcitrant disease. The alopecia is permanent once scarring is established, underscoring the value of early, adequate treatment to limit irreversible follicular loss. Long-term control rather than cure is a realistic therapeutic goal for most patients, and quality-of-life impairment is substantial.

• The name is a misnomer: DCS is a follicular-occlusion, immune-mediated disease, not a primary infection — antibiotics work largely through anti-inflammatory effects
• Look for and manage coexisting hidradenitis suppurativa and acne conglobata; they share pathophysiology and may respond to the same biologics
• Boggy scalp with cross-communicating sinus tracts (pus expressed from a distant opening) is the clinical signature
• Because scarring alopecia is irreversible, prioritize early systemic control; isotretinoin remains first-line, with TNF-α inhibitors the best-evidenced escalation
• Biopsy any chronic non-healing or indurated area to exclude squamous cell carcinoma