What is your diagnosis for this 50-year-old woman?

She referred for treating the scar on her forehead which was there since years ago following a car accident. On examination the erythema and swelling of the scar was unusual for an old scar and the patient confirmed that it was not red till a few months ago.

Diagnosis: Scar Sarcoidosis

Scar sarcoidosis is a specific manifestation of sarcoidosis, occurring in 5.4-13.8% patients of cutaneous sarcoidosis in adults.  It has been found to occur at the scar sites of pseudofolliculitis barbae, Kveim test biopsy site, tuberculin test site, tattoos, venipuncture, mechanical trauma, radiation, herpes zoster, and following hyaluronic acid injection. How the old scars, as reported up to 60 years after their onset, develop into a nidus of sarcoidal granuloma is not known. They may appear early before pulmonary involvement or parallel chronic systemic findings.  Previous contamination of scar with foreign material possibly at the time of trauma has been suggested to be an underlying cause. Persistent granulomatous reaction to vaccines and allergen-extract preparation for desensitization are usually attributable to the adsorbing agent aluminium hydroxide.

Scar sarcoidosis is characterized by reoccurrence of activity at the site of previous scar and clinically represented by swelling, erythema, and purplish red hue that subsequently turn brown with the conspicuous absence of itching.  This factor is important in differentiating between scar sarcoidosis from hypertrophic scar and keloid, which are the clinical mimickers. It occurs during the acute eruptive phase of sarcoidosis paralleling changes in the lung or can occur at the late phase as a sign of exacerbation in a previously quiescent sarcoidosis.

Chronic active systemic sarcoidosis along with iritis has been estimated to coexist in 84.6% of scar sarcoidosis patients in contrast to around 30% patients with other form of cutaneous sarcoidosis having systemic involvement.  Even though there is no systemic involvement at the onset, 30% of patients may develop systemic manifestations in long-term follow up.

In the absence of systemic involvement, scar sarcoidosis can be managed with topical or intralesional corticosteroids. For those patients who have systemic involvement, hydroxychloroquine is the first-line drug of choice. Prednisolone and methotrexate are the second-line choices. Other drugs which can be used are tetracyclines, isotretinoin, allopurinol, thalidomide, leflunomide, pentoxifylline, and infliximab, etc.

In conclusion, scar sarcoidosis has two important clinical implications associated with it. First, it can be very easily confused with hypertrophic scar or keloid. Second, scar sarcoidosis is an important clue to the significant risk of systemic involvement due to disease.

  Dr. Reza Ghaderi,

Associate Professor of Dermatology,