Repeated invasive pneumococcal infections in young children without apparent underlying immunodeficiency.

During a 30-month interval at LeBonheur Children's Medical Center, 394 patients had a blood or cerebrospinal fluid culture positive for Streptococcus pneumoniae. Sixteen of these episodes (4%) were repeated infections; 6 of these 16 patients had sickle cell disease. Six of the remaining 10 patients had immunologic evaluations of varying completeness; no immunodeficiency was identified by these tests or on follow-up. Nine of the ten previously healthy patients with repeated pneumococcal disease were less than 2 years of age. In our experience, repeated invasive pneumococcal infections in otherwise healthy young children were relatively common (10/394, or 2.5% of patients with invasive pneumococcal infections) and did not indicate the presence of an unsuspected immunodeficiency.

Cell-mediated immune status of children with recurrent infection.

OBJECTIVE: To evaluate the cell-mediated immune status of children with recurrent respiratory tract infections. DESIGN: We evaluated the cell-mediated immune status of 76 patients referred because of recurrent infection. Patients were divided into those with serologic abnormalities and those without such findings. Twenty-three healthy children served as control subjects. Studies of lymphocyte phenotype included CD4+ CD29+ cells (an immunologically mature phenotype), lymphocyte proliferation studies, cytokine production including interleukin-2 (IL-2), IL-4, IL-6, and interferon gamma), and measurement of in vitro IgM and IgG synthesis. RESULTS: Lymphocyte proliferation and T-cell phenotype were similar in both patient groups as well as in control subjects. The proportions of CD4+ CD29+ cells at different ages were similar in all groups. Patients with serologic abnormalities (e.g., partial IgA deficiency, partial IgG subclass deficiency) produced more IL-2 and IL-4 than did other patients. The control population had greater spontaneous IgM and IgG synthesis than the patient groups. CONCLUSION: Routine studies of T-cell function of patients with recurrent infection provide little information useful in making clinical decisions.

Role of immunoglobulin subclasses and specific antibody determinations in the evaluation of recurrent infection in children.

We studied humoral immune function in 267 children with recurrent respiratory infections referred to our immunology clinic to determine the most appropriate immunologic studies for evaluating recurrent infections in children. Of this highly selected population, 58% had a partial deficiency in one or more of the major immunoglobulin isotypes or IgG subclasses (defined as at least 2 SD below the normal age-adjusted mean). In none of the patients was there a total absence of an immunoglobulin isotype. The most common abnormality was partial IgA deficiency, which was found in one third of the patients. Twenty-six patients had only partial IgG subclass deficiencies, of which 20 were deficiencies of a single subclass. IgG1 was an isolated partial defect in three patients, IgG3 in five patients, and IgG2 and IgG4 were selective partial defects in six patients each. Tetanus toxoid and pneumopolysaccharide type 3 were the most immunogenic of the immunogens tested; hyporesponsiveness to pneumococcal polysaccharide types 7, 9, and 14 was common. Nineteen percent of the patients with normal immunoglobulin concentrations who were tested had lower-than-expected antibody titers; 42% of those tested with partial isotype deficiencies had deficient antibody responses. Of 25 patients with selective partial IgG subclass deficiencies or combined IgG subclass deficiencies, eight had antibody deficiencies. Our findings indicate that a high proportion of children referred to immunology clinics for recurrent infection have a demonstrable immunologic abnormality. Selective IgG subclass deficiency or a combined IgG subclass deficiency without an associated deficiency in a major immunoglobulin isotype is unusual. Identification of such patients is not predictive of the capacity to form antibodies to the antigens tested in this study and, in our opinion, adds little to the initial evaluation of immune function in such children.

Molecular analysis of X-linked agammaglobulinemia with growth hormone deficiency.

To address the relationship between the gene (or genes) that causes the syndrome of X-linked hypogammaglobulinemia with isolated growth hormone deficiency and the gene responsible for typical X-linked agammaglobulinemia (XLA), we have used cytogenetics, examination of X chromosome inactivation patterns in potential carriers of the defect, and linkage analysis to study two unrelated families in which the affected males had isolated growth hormone deficiency and immunologic findings indistinguishable from those of typical XLA. A deletion could not be demonstrated in either family by G-banded karyotypes or flow cytometric analysis of metaphase chromosomes. Studies of X inactivation showed that mothers of affected boys from both families exhibited selective use of a single X chromosome as the active X chromosome in B cells but not T cells. This pattern is the same as that seen in obligate carriers of typical XLA. Linkage analysis demonstrated the most likely location for this gene (or genes) to be the midportion of the long arm of the X chromosome between DXS3 and DXS94. This segment of the X chromosome, which constitutes approximately 5% of the total X chromosome, encompasses the gene for XLA. These findings are consistent with the combination of XLA and growth hormone deficiency being caused by a small, contiguous, gene deletion syndrome involving the gene for XLA or an allelic variant of the gene for typical XLA.

Chronic mucocutaneous candidiasis in childhood and complications of non-Candida infection: a report of the Pediatric Immunodeficiency Collaborative Study Group.

We reviewed the clinical course in 43 patients from eight medical centers who were given the diagnosis of chronic mucocutaneous candidiasis, a rare disorder of unknown cause that may occur in childhood. Recurrent or severe infections with organisms other than Candida were seen in 80% of the patients. There were nine cases of septicemia. Seven patients have died; six of these deaths were directly related to non-Candida infectious complications. Endocrine dysfunction, including Addison disease (11 patients) and hypothyroidism (9 patients), was seen in 19 of 43 patients. Immunologic studies failed to reveal a consistent abnormality, although two of five patients with reversed T4/T8 ratios are among those who have died. Ketoconazole was effective in controlling symptoms of candidiasis in most patients. The findings from this study indicate that non-Candida infections cause serious morbidity and may result in death in patients with chronic mucocutaneous candidiasis.

Prediction of persistent immunodeficiency in the DiGeorge anomaly.

To assess the natural history of the immune defect in DiGeorge anomaly, we reviewed serial immunologic studies in 18 patients. The diagnosis was made with criteria based on the concept of the DiGeorge anomaly as a field defect. Initial or early follow-up laboratory examination suggested moderate to normal T cell function in 14 patients. None of these patients have lost T cell capability; they have never had infections characteristic of T cell deficiency. Four patients had clinical and laboratory evidence of profound immunodeficiency. A decreased number of CD4+ cells (less than 400/microliters) and a decrease in phytohemagglutinin responsiveness (stimulation index less than 10) may be useful in discriminating patients with immunodeficiency; absolute lymphocyte count and immunoglobulin values were not informative. At the time of surgery, the thymus was not found in 11 of 14 patients; however, only two of these patients had immunodeficiency. Patients with a persistently low number of CD4+ cells and decreased phytohemagglutinin response are candidates for immunologic reconstitution.

Infantile hypophosphatasia: normalization of circulating bone alkaline phosphatase activity followed by skeletal remineralization. Evidence for an intact structural gene for tissue nonspecific alkaline phosphatase.

After a 3-month course of weekly intravenous infusions of pooled normal plasma in an attempt at enzyme replacement therapy, we observed gradual and prolonged normalization of circulating alkaline phosphatase (AP) activity in a boy with infantile hypophosphatasia. During this 4-month period, when hypophosphatasemia had been corrected, electrophoretic and heat denaturation studies suggested that the AP in serum was skeletal in origin. Serial radiographic and histologic studies of bone demonstrated skeletal remineralization and the appearance of AP activity in osteoblasts and chondrocytes after the infusions. Considerable clinical improvement coincided with the skeletal remineralization. Our observations indicate that in one patient with infantile hypophosphatasia the structural gene for the tissue-nonspecific (bone/liver/kidney) AP isoenzyme was intact and could be expressed with marked physiologic effect. Infantile hypophosphatasia may result from absence or inactivation of a circulating factor(s) that regulates the expression of the gene for tissue nonspecific AP.

Enzyme replacement therapy for infantile hypophosphatasia attempted by intravenous infusions of alkaline phosphatase-rich Paget plasma: results in three additional patients.

After biochemical and radiographic studies, enzyme replacement therapy in three patients with the infantile form of hypophosphatasia was attempted by weekly intravenous infusions of bone alkaline phosphatase-rich (BAP) plasma from patients with Paget bone disease. Subsequently, circulating BAP activity was substantially increased in each patient, and in one was maintained in the normal range for nearly 2 months. Despite partial or complete correction of the deficiency of circulating BAP activity, we observed no radiographic evidence for arrest of progressive osteopenia or improvement in rachitic defects in any of the patients. Failure of infants with hypophosphatasia to show significant healing of rickets on correction of circulating BAP activity supports the hypothesis that this isoenzyme functions in situ during normal skeletal mineralization.