This may occur in ATTR cases where circulating kappa IgLCs can contaminate TTR fibrils, or in AL cases where kappa or lambda IgLCs can produce a nest effect and attract circulating wild-type TTR, or especially when a monoclonal gammopathy of undetermined significance (MGUS) coexists with ATTR, which can occur in 10–49% of patients (97). The gene discussed is TTR; the disease is monoclonal gammopathy.