Dissecting cellulitis

Dissecting cellulitis of the scalp (DCS) is a rare chronic inflammatory disease of scalp hair follicles manifesting as multiple painful nodules and abscesses that interconnect via sinus tracts. The condition tends to run a progressive course that eventually results in scarring alopecia.

This chapter is set out as follows:

• Unknown, although it is thought that a blockage of hair follicles leads to inflammation and secondary infection

• Predominantly in males aged between 18 and 40 years
• More common in skin of colour 
• Familial cases are exceptional, as is childhood onset

Distribution

• Most commonly the vertex and occiput, although the entire scalp may be involved

Morphology

• The condition may start with pustules that may group together and form abscesses or nodules
• Painful, firm, skin‐coloured nodules 1-4 cm in diameter develop, later becoming softer and fluctuant
• Confluent nodules form tubular ridges with an irregular cerebriform pattern
• The nodules may develop sinuses with purulent, often foul-smelling discharge. Pressure on one pole will often express pus at a distal pole
• Characteristically, hair is lost from the summit of the lesions and retained in the valleys
• Significant cervical lymphadenopathy is often absent  
• Late-stage lesions scar

Associations

• In some cases - acne and hidradenitis suppurativa
• An asymmetrical peripheral and axial arthritis occurs with sacroiliitis in 73%

• Cultures of the pus and also hair follicles including the roots (or a vigorous surface rub using for example a disposable toothbrush) must always be done to rule out fungal infection
  

• Skin biopsies are only needed if there is diagnostic uncertainty 

• Patients need to be referred urgently to Secondary Care. At the same time commence treatment with either lymecycline 408 mg BD or doxycycline 100 mg BD, along with a topical antiseptic wash such as chlorhexidine. Provide a patient information leaflet

• The mainstay of treatment in Secondary Care is isotretinoin (1 mg kg daily), in combination with prednisolone (0.5–1 mg/kg daily) and erythromycin (500 mg four times daily) in order to try and induce a rapid remission and significant hair regrowth in areas not yet irreversibly damaged. The antibiotics can be stopped after 4 weeks and the prednisolone gradually tailed off and replaced by topical steroids. The isotretinoin should be continued for at least 6 months, and reintroduced if the condition relapses. In more localised cases intralesional corticosteroids can be considered instead of prednisolone. Other treatments reported as having some efficacy include dapsone 

• In recalcitrant cases biologic therapy can be used, or widespread excision and grafting may be considered