Chapter 40: Dissecting Cellulitis of the Scalp

SUMMARY

• Dissecting cellulitis (DC) is a rare chronic suppurative disease that affects the terminal hairs mainly of the nape and vertex, causing obstruction and rupture of the acroinfundibulum, which triggers a strong inflammatory reaction.

• DC mostly affects young males (range 18–40 years), especially African or Caribbean descents. Follicular occlusion disorders, including hidradenitis suppurativa, acne conglobata, and pilonidal sinus are common comorbidities and share high BMI and active smoking as mutual risk factors.

• Early lesions consist of sterile follicular pustules, which later evolve into boggy nodules with reversible hair loss, mimicking alopecia areata. Suppurative and fibrotic stages are characterized by interconnecting fistulas between draining abscesses and deep tissue remodeling, which results in cicatricial alopecia and hypertrophic scarring.

TIPS FOR DIAGNOSIS

• DC diagnosis relies on clinical examination, even though early stages pose a clinical challenge and may be unmasked by the aid of trichoscopy.

• The prognosis of hair loss is easily provided by trichoscopy, which is able to differentiate early suppurative stages from cicatricial ones.

TIPS FOR TREATMENT

• Medical management is based on antibiotics or oral isotretinoin and aims to slow down disease progression and scarring, treat acute flares, and relieve the patient’s symptoms.

• Despite the high clinical response rate to medical treatments, the disease evolution is wax and wane, since relapses upon drug discontinuation are frequent.

• Surgery is highly invasive but resolutive. It is advocated in case of aesthetic disfigurement or repetitive medical failure; the residual baldness may be treated with hair transplantation only in a burnt-out stage.

DON’T FORGET

• Combine medical and procedural therapy to address disease evolution and acute flares.

• Inspect the rest of the body surface to check for associated signs of hidradenitis suppurativa; you can treat two conditions with the same drugs.

PITFALLS AND CAUTIONS

• Be cautious when making a long-term prediction concerning medical therapy.

• DC cases with a high degree of inflammation scheduled for oral isotretinoin may benefit from a short steroid course to downregulate inflammation.

• In the setting of recalcitrant DC, take into account off-label therapies and discuss with the patient their use or combination with a second cycle of antibiotic or oral isotretinoin.

• Do not purpose hair restoration surgery if there are even minimal signs of disease reactivation.

EXPERT PEARLS

• Always perform trichoscopy when suspecting DC; the heterogeneity of the trichoscopic findings is itself a clue for diagnosis.

PATIENT EDUCATION POINTS

• Use shampoo with mild antiseptics to prevent superinfection.

• Avoid close haircuts or shaves.

• Behavioral modifications, including smoking cessation or weight loss, are advisable.