BTK and hyperinsulinemic hypoglycemia, familial, 4: However, BTK variants associated with atypical XLA case presentations have been reported, in patients with normal: IgG levels (21), selective IgM deficiency (22) with a leaky phenotype (in a Japanese family) (23), a diagnosis in adulthood but with a history of recurrent infections (24) and with impaired polysaccharide responsiveness without marked hypogammaglobulinemia (25).