Linear lupus panniculitis of the scalp presenting as alopecia along Blaschko's lines: a distinct variant of lupus panniculitis in East Asians?

A 32-year-old Taiwanese man presented to our clinic with a 6-month history of linear hair loss in a wavy and curved pattern across the parietal and occipital scalp, resembling the distribution of Blaschko's lines. Physical examination showed interfollicular erythema and follicular plugging without skin atrophy or sclerotic change. Histopathology revealed a lymphoplasmacytic infiltrate in the perifollicular dermis and subcutis with abundant mucin deposition, consistent with the diagnosis of lupus panniculitis. Treatment with hydroxychloroquine and local steroid injection resulted in complete hair regrowth but recurrence was noted. Linear lupus panniculitis of the scalp presenting as alopecia along Blaschko's lines had so far been reported exclusively in five East Asians. Apart from classical lupus panniculitis, it had distinct clinical and histopathological features such as younger age of onset, male predominance, reversible clinical course without scarring, fewer associations with systemic lupus erythematosus, exclusive involvement of scalp, sparse inflammatory infiltration, abundant mucin deposition, higher degree of hyaline fat degeneration and negative results of immunofluorescent studies. Therefore, we propose linear lupus panniculitis of the scalp to be a distinct variant of lupus panniculitis and should be included in the differential diagnosis for focal or linear alopecia, especially in East Asians.