Derm Dx: Recurring pus bumps on the scalp

Dissecting cellulitis of the scalp, also known as perifolliculitis capitis abscedens et suffodiens (PCAS), is an inflammatory and suppurative disease of hair follicles on the scalp with a chronic and recurrent presentation.Patients present with multiple painful, purulent cutaneous nodules and...

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Dissecting cellulitis of the scalp, also known as perifolliculitis capitis abscedens et suffodiens (PCAS), is an inflammatory and suppurative disease of hair follicles on the scalp with a chronic and recurrent presentation.

Patients present with multiple painful, purulent cutaneous nodules and abscesses interconnected by draining sinus tracts. The cause of the disease is likely from occlusion of the hair follicle, where accumulation of sebaceous and keratinous matter causes dilation of the follicle and eventual rupture, resulting in a neutrophilic and granulomatous inflammatory response.¹

Secondary infection with microorganisms of the skin is often seen, most commonly with Staphylococcus aureus, Staphylococcus epidermidis, and Propionibacterium acnes.

The disease is uncommon, presenting mainly in black males. Unfortunately, treatment is difficult and the prognosis of the disease is poor; its chronic course can eventually result in scarring and likely permanent alopecia. Furthermore, relapse is common in PCAS, though there have been cases of spontaneous resolution.

Management of PCAS is problematic and the treatment options used are either ineffective or are not permanently successful.

The current treatment of choice is oral isotretinoin given for four months at 1mg/kg/day and then for another six months at 0.75 mg/kg; this is followed by treatment for another four months after clinical inactivity to prevent relapses.¹

There have also been case reports of oral acitretin, oral alitretinoin, and oral isotretinoin combined with either rifampicin or dapsone having successful results.¹

Although not a standard treatment since infection is secondary, antibiotics such as doxycycline, ciprofloxacin, rifampicin, and dapsone can also be administered. ¹

Thirdly, injection of intralesional corticosteroids such as triamcinolone acetonide into lesions and nodules can be helpful in reducing inflammation, but the effects are not permanent, and this therapy is only a temporary one.

There have also been case reports of the effectiveness of adalimumab and other biological agents such as infliximab in targeting inflammation and reducing the levels of tissue destruction.² Continuous long-term treatment is often required to prevent relapse.

Non-medicational treatments include carbon dioxide laser ablation therapy, x-ray epilation of hair follicles, which has been successful in some cases but is not recommended at this time, and surgical excision for severe or refractory cases. The surgical treatment of choice is wide excision of lesions and split-thickness skin grafting.¹

Nrithya Sundararaman, BS, is a medical student at Baylor College of Medicine.

Adam Rees, MD, a graduate of the David Geffen School of Medicine at UCLA, practices dermatology in Los Angeles.