Complete Clq Deficiency Associated with IgG Multiple Myeloma

We report a case of IgG multiple myeloma with selective complete Clq deficiency. The patient was a 75-year-old Japanese woman who exhibited urticaria on the arm and an absence of serum hemolytic complement activity (CH50). Further studies revealed no vasculitis in the urticarial lesion but showed selective complete deficiency of Clq without low molecular weight Clq precipitin. Addition of highly purified Clq restored the CH50 level of the patient's serum to normal. It is suggested that this abnormality was a primary Clq deficiency. We discussed a relationship between the Clq deficiency and myeloma and reviewed the literature.