Volume 124, Issue 6 , Pages 1363-1364.e1, December 2009
Diagnosis of primary immunodeficiency: Let your eyes do the talking
Article Outline
Key words: Primary immune deficiency, physical diagnosis, Shwachman-Bodian-Diamond syndrome, pectus carinatum, B cells
Abbreviations used: NK, Natural killer, SBDS, Shwachman-Bodian-Diamond syndrome
Every screening evaluation for primary immunodeficiency must include a physical examination of the patient because the powers of observation should direct the evaluation for several types of primary immunodeficiency.1, 2 For example, simple inspection of the patient for growth, lymphoid tissue (X-linked agammaglobulenemia), telangiectasias (ataxia-telangiectasia), abnormal facies (DiGeorge syndrome), chronic eczema (Wiskott-Aldrich syndrome, hyper-IgE syndrome, and immune dysregulation polyendocrinopathy enteropathy X-linked syndrome), pale skin and photophobia (Chediak-Higashi syndrome), or severe gingivostomatitis (leukocyte adhesion defect) allow for proper direction toward making the diagnosis of primary immunodeficiency.
Case report
We present here the example of a 4-year-old girl whose initial presentation to medical attention was a result of repeated lower respiratory infections, short stature, failure to thrive (height, weight, and body mass index less than fifth percentile for age), and a chest deformity (Fig 1, A). The family history revealed no similar problems.
Fig 1.
A, Pectus carinatum. B, Computed tomograph of chest. C, Bone marrow biopsy specimen (hematoxylin-eosin stain, ×100 magnification).
Skeletal survey and chest radiographs revealed generalized skeletal dysplasia with irregularity of the metaphyses along the cartilage plates of the proximal humeri, proximal and distal femurs, and proximal tibias; marked cupping of the anterior ends of the ribs; and blunted iliac crests (not shown). A significant delay in bone age (36 months vs actual age 50 months) was determined by the method of Greulich and Pyle.
Computed tomography of the chest demonstrated an increased anterior-posterior chest wall diameter and bilateral atelectasis most prominent in the left lower lobe of the lung (Fig 1, B). An abdominal ultrasound revealed no abnormalities.
A complete blood count with differential revealed significant neutropenia (570 neutrophils/μL; normal age-matched range, 1500-8000 cells/μL) with a normal absolute lymphocyte count (2860 cells/μL; normal age-matched range, 2300-5400 cells/μL). Platelet counts were slightly decreased. A bone marrow biopsy specimen was moderately hypocellular for age (Fig 1, C), but residual tri-lineage hematopoiesis was present with orderly maturation and without significant dysplasia (not shown). The myeloid and erythroid precursors were decreased on microscopic analysis of the bone marrow aspirate smear (not shown).
An infectious diseases workup including evaluation for parvovirus, cytomegalovirus, and EBV infections proved to be negative. In addition, a full gastroenterologic workup showed a low-normal pancreatic amylase level of 3 IU/L (normal range, 0-60 IU/L), a low level of serum trypsin at 39 ng/mL (level consistent with chronic pancreatitis), and low levels of fat-soluble vitamin A at 0.13 mg/L (normal range, 0.2-0.5 mg/L) and vitamin D at 19 ng/mL (normal range, 30-80 ng/mL); vitamins E and K levels were normal. Stool studies for fecal elastase were normal without excess fat in the stools, and diarrhea was not prominent.
A diagnosis of Shwachman-Bodian-Diamond syndrome (SBDS) was entertained, and evaluation of the patient's immune system was obtained. Serum immunoglobulin levels demonstrated normal levels of IgG and IgM, slightly low IgA, and mildly elevated IgE. Antibody responses to protein antigens were normal to diphtheria, hemophilus, tetanus antigens (normal ≥0.1 IU/mol each) and 2 of 14 pneumococcal serotypes (normal ≥1.0 μg/mL each; data not shown).
PBMC phenotyping demonstrated an inverted CD4/CD8 T-cell ratio, a paucity of B cells (CD19+ cells, CD20+ cells, and CD19+CD27+[memory cells]), a low percentage of natural killer (NK) cells (CD3-CD56+CD16+), and low values for CD4+ memory (CD4+CD45RO+) T cells (Table I). Lymphocyte proliferation assays to mitogens and antigens in vitro stimulation were normal (data not shown).
Table I. Lymphocyte phenotyping
| Percent of total gated population | ||||
|---|---|---|---|---|
| Monoclonal phenotypes | Patient | Normal range 2-5 y | Patient #/mm^3 | Normal range #/mm^3 2-5 y |
| CD3-CD56+CD16+ | 1.4 | 3.0-18.6 | 39 | 123-785 |
| CD2+ | 98.1 | 69.8-93.2 | 2803 | 884-2800 |
| CD3+ (total) | 97.7 | 58.0-74.0 | 2791 | 1656-3841 |
| CD3+CD4+ | 44.5 | 28.0-47.2 | 1272 | 871-2379 |
| CD3+CD8+ | 53.3 | 16.0-31.8 | 1524 | 518-1433 |
| CD19+ | 0.8 | 12.8-30.06 | 23 | 421-1397 |
| CD20+ | 0.5 | 2.7-24.9 | 14 | 59-457 |
| CD19+CD27+ | 0.3 | 1.0-5.2 | 9 | 19-131 |
| CD4+CD45RA+ | 39.2 | 3.3-32.9 | 1121 | 134-969 |
| CD4+CD45RO+ | 4.9 | 15.6-41.8 | 141 | 301-919 |
| CD4/CD8 ratio | 0.83 | 0.72-2.94 | ||
Genetic sequencing analysis revealed a heterozygous mutation in genomic DNA, indicating the presence of a possible deleterious mutation in exon 1 of the SBDS: 98A>C gene that results in p.K33 T (changes lysine to threonine) not previously reported. Chromosomal microarray (105 K oligonucleotide) and specific studies for cartilage hair hypoplasia, chromosomal breakage syndrome, Russell-Silver syndrome, and Pearson syndrome (mitochondrial DNA disorder) revealed no abnormalities.
Discussion
Shwachman-Bodian-Diamond syndrome is characterized by metaphyseal skeletal dysplasia, exocrine pancreatic insufficiency, and varying degrees of cytopenias, predominantly neutropenia. To date, the immune dysfunctions that have been reported include varying degrees of T-cell, B-cell, and NK-cell defects. The most widely reported deficits are3, 4 (1) neutropenia and inability of neutrophils to orient and migrate toward a chemoattractant gradient; (2) T-cell defects with decreased number of total circulating T lymphocytes and inverse CD4:CD8 ratio; (3) decreased proportions of circulating B cells with low immunoglobulins, decreased in vitro B-cell proliferation, and lack of specific antibody production; and (4) decreased percentages of circulating NK cells.
The presence of serum immunoglobulin and virtual absence of circulating B cells is unusual but not unknown.5 Our patient's unique profile is possibly a result of B cells present in the lymphoid tissue but not found in the peripheral blood circulation.
Gene sequencing for the SBDS gene showed only 1 heterozygous mutation on exon 1, which was presumed to be pathogenic. Mutations in this gene only account for as much as 70% to 75% of known affected individuals.6 It is possible that other causative genes for SBDS or undetected deletions or duplications of the SBDS gene may be playing a role in this patient (see this article's Discussion section in the Online Repository at www.jacionline.org for additional comments).
In summary, the experience with this patient who presented with clinical and physical findings of short stature, growth failure, and pectus carinatum illustrates the importance of physical examination in guiding the workup for immunodeficiency.
Discussion
Approximately 75% of the patients with SBDS are accounted for by mutations in the SBDS gene.6 Most of these mutations result from gene conversion events that introduce mutated sequences from a pseudogene into the SBDS gene. In 90% of cases, SBDS patients will at least test positive for at least 1 gene mutation.6 For mutation analysis, exons 1 to 5 of the SBDS gene plus 20 bases into the 5′ and the 3′ ends of all introns were analyzed by a commercial laboratory. In this patient, a heterozygous 98A>C mutation was detected in genomic DNA. This test indicates the presence of a possible deleterious mutation p.K33 T in exon 1 of the SBDS gene that changes lysine to a threonine, which has not been previously reported. The second mutation was not found. SBDS is an autosomal-recessive disorder that results in most cases from homozygous mutations of the SBDS gene on chromosome 7.2 It is possible that other mutations have not yet been uncovered, perhaps by the limitations of our testing, or perhaps by mutations in other unaccounted for genes. Further testing of the patient will include a single nucleotide polymorphism array to determine possible intragenic deletions or duplications of the other SBDS allele. Other testing done included a chromosomal oligonucleotide microarray (105 K) that showed no obvious deletions or duplications involving large segments of the gene. In addition, gene sequencing for the RMRP gene (cartilage hair hypoplasia), chromosomal breakage syndrome studies, Russell-Silver syndrome methylation studies, and Pearson bone marrow–pancreas syndrome (mitochondrial DNA deletion panel) revealed no abnormalities.
Gene sequencing for the SBDS gene showed only 1 heterozygous mutation on exon 1, which was presumed to be pathogenic. However, no additional mutation was found. To this date, not all mutations are found in SBDS gene. It is possible that other causative genes for SBDS may be playing a role in this patient. The diagnosis of SBDS in this child is strongly suggested by the characteristic metaphyseal involvement, the failure to thrive, the marrow abnormality, and the pancreatic involvement.
References
- Improving cellular therapy for primary immune deficiency diseases: recognition, diagnosis and management. J Allergy Clin Immunol. 2009;124:1152–1160
- . Shwachman-Diamond syndrome: a review of the clinical presentation, molecular pathogenesis, diagnosis, and treatment. Hematol Oncol Clin North Am. 2009;23:233–248
- . Shwachman-Diamond syndrome. Pediatr Blood Cancer. 2005;45:892–901
- . Shwachman-Diamond syndrome associated with hypogammaglobulinemia and growth hormone deficiency. J Allergy Clin Immunol. 1995;96:247–250
- . B-lymphocyte deficiency and neutropenia in a patient with normal immunoglobulins. J Allergy Clin Immunol. 2009;123:S14
- Mutations in SBDS are associated with Shwachman-Diamond syndrome. Nature Genet. 2003;33:97–101
Supported by the Primary Immune Deficiency Treatment Consortium (U54 AI082978) and the David Center at Texas Children's Hospital, Houston.
Disclosure of potential conflict of interest: C. Bacino has received research support from the National Institutes of Health and has provided legal consultation or expert witness testimony regarding brain injury causation and genetic etiologies. The remaining authors declare that they have no relevant conflicts of interest to disclose.
PII: S0091-6749(09)01615-7
doi:10.1016/j.jaci.2009.10.049
© 2009 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.
Volume 124, Issue 6 , Pages 1363-1364.e1, December 2009
