Dissecting cellulitis is considered part of the follicular occlusion triad that also includes acne conglobata and hidradenitis suppurativa. In some patients, only the scalp hair follicles are affected. As a follicular occlusion disorder, there is a defect in normal keratin production in the hair follicles. As a result, the hair follicles become obstructed by oil (sebaceous contents) and keratin debris. Ultimately the follicles burst resulting in an intense inflammatory reaction. It has been suggested that the cause of dissecting cellulitis may involve an abnormal host response to bacteria. However, patients with dissecting cellulitis have no evidence of immune deficiency or presence of infection at other skin sites.
Signs & Symptoms
It is seen primarily in dark-skinned men in the second to fourth decade of life.
It frequently begins in the posterior scalp or crown although any region of the scalp may be involved. It is characterized by multiple painful sometime fluid filled nodules, interconnecting sinus tracts, and purulent drainage may be present over large areas of the scalp. The condition tends to be chronic and progressive, and ultimately leads to scarring and extensive hair loss.
Diagnosis & Treatments
Experienced dermatologists will suspect the diagnosis of dissecting cellulitis from a detailed clinical history, thorough physical examination of the scalp, bacterial cultures, and a scalp biopsy. It is important to know if the patient has a history of recurrent S. aureus
or other bacterial infections. A scalp biopsy the gold standard of diagnosis of scarring hair loss and are often performed when considering a diagnosis of dissecting cellulitis. The most helpful information from the biopsy is the type and pattern of inflammation (mixed type), presence of scarring and the sometimes the presence of bacterial pathogens. A bacterial culture from a pustule or a tissue culture from the scalp tissue can be helpful in determining the best treatment plan. A fungal culture may also be performed to rule out tinea capitis (fungal infection of the scalp).
Early diagnosis and therapeutic intervention can often prevent permanent damage to hair follicles. Once a definitive diagnosis is made, we can determine the best treatment plan for each individual. Some regrowth is even possible with treatment.
Treatment of dissecting cellulitis is challenging in terms of permanent arrest of the condition and full hair regrowth. In patients with a positive bacterial culture, antibiotics should be directed at eradication of that organism. In patients with a negative bacterial culture, oral isotretinoin may be helpful, though it must be started in small doses to prevent worsening inflammation. However, relapses are frequent upon discontinuation of the above medications, and treatment is invariably long-term. Partial hair regrowth may occur if the condition is treated early.
Recently several reports have shown favorable response to anti-tumor necrosis factor (TNF) therapy for dissecting cellulitis and hidradenitis suppurativa. Infliximab and adalimumab have been used in a small number of patients with dissecting cellulitis with good results while on therapy. However, relapses are common when the drugs are discontinued, and the underlying sinus tracts are not altered. Long-term medical treatment combined with surgical drainage and resection of affected areas are often needed in dissecting cellulitis.