Over the next 3 years she suffered from recurrent sinusitis, otitis media, chest infections (sputum cultures positive

for Moraxella catarrhalis and Haemophilus species) and viral warts. She has a sister with features of DBA – low haemoglobin at 10·4 g/dl, raised mean corpuscular volume (MCV), lymphopenia, elevated fetal haemoglobin (HbF) (3%), high erythrocyte adenosine deaminase (eADA) levels, mildly reduced T cell numbers and slight reduction in proliferative responses to standard mitogens. The sister’s immunoglobulin levels, including functional antibody levels, are normal and she has not required any specific therapy for her anaemia. Investigations in infancy showed a normocytic DNA Damage inhibitor anaemia, normal serum immunoglobulins [IgG 7·3 g/l (normal range 3·0–10·5), IgA 0·28 g/l (0·1–1·2), IgM 1·07 g/l (0·3–1·5)] and good vaccine responses to conjugated Haemophilus influenzae type b and unconjugated pneumococcal polysaccharide vaccines. By the age of 9, serum IgG levels had dropped to 4·94 g/l (normal range 6·0–13·0). Lymphocyte proliferation responses to phytohaemagglutinin, pokeweed mitogen, OKT3, tetanus, varicella Proteases inhibitor and herpes antigens were reduced. Intravenous immunoglobulin (IVIG) replacement therapy was commenced, and stopped after 8 years for reassessment of immune function. Four years later, she had persistent anaemia (Hb 10·0 g/dl, MCV 95·6fl) and low IgG (3·37 g/l), IgA (0·96 g/l) and IgM (0·79 g/l). Bone marrow cytogenetic

studies

were normal, excluding microdeletions in 19q13 and 5q- syndrome. Specific antibody tests showed absent antibodies against measles and reduced tetanus and pneumococcal antibody levels. She was diagnosed to have common variable immunodeficiency as no other causes of low IgG and low levels of specific antibodies were identified. High resolution CT scan chest showed evidence of right middle lobe bronchiectasis and bilateral lower lobe bronchiectasis worse on the left. Intravenous immunoglobulin therapy was recommenced at this stage. Lymphocyte subset analysis showed lymphopenia at 833 × 106/µl (normal range 1500–3500), CD3+ T cells 536 (800–2700), helper CD4+ T cells 291 (400–1700), cytotoxic CD8+ T cells 191 (300–1200), CD19+ B cells 158 (100–600) and CD16+CD56+ science natural killer cells 32 (90–600). B cell studies showed a reduced class-switched memory B cell subset at 2·5%. Lymphocyte proliferation responses to OKT3, phytohaemagglutinin and pokeweed mitogen remained reduced (see Table 1). Peripheral blood eADA level performed recently was high at 594 (normal range 40–100 u/l), consistent with the diagnosis of DBA. She has remained well on home therapy with weekly subcutaneous immunoglobulin infusions over the last 3 years. Polymerase chain reaction (PCR)-based methods for mutation detection.  Genomic DNA was extracted from the patient’s leucocytes with a commercial DNA purification kit, as per the manufacturer’s instructions.