The biopsy specimen displayed minimal hyperkeratosis with mild focal basilar vacuolopathy and rare necrotic keratinocytes, as well as an angiocentric, mixed-cell, superficial inflammatory infiltrate consisting of lymphocytes, occasional plasma cells, and neutrophils. Immunologic evaluation of the patient revealed a depressed total complement activity (CH50) of 0.04 (reference range, 0.70-1.50), with a C2 level of less than 0.01 g/L (reference range, 0.2-0.4 g/L). C3 and C4 levels were within normal limits, as were IgG subclasses. Other laboratory tests revealed a negative antinuclear antibody titer, a positive anti-Ro antibody titer, normal findings on urinalysis, and normal complete blood cell count. Screening of additional family members revealed a normal CH50 level in the mother; however, the father and sister had depressed CH50 levels, and the sister's C2 level was well below normal.
Malar Rash in a Child—Diagnosis. Arch Dermatol. 1999;135(10):1267-1272. doi:10.1001/jamadermatol.58603