Genetic heterogeneity in patients with X-linked recessive chronic granulomatous disease

Primary Immunodeficiencies

Primary immunodeficiencies (PIDs), once considered to be very rare, are now increasingly recognized because of growing knowledge in the immunological field and the availability of more sophisticated diagnostic techniques and therapeutic modalities [161]. However in a database of >120,000 inpatients of a general hospital for conditions suggestive of ID 59 patients were tested, and an undiagnosed PID was found in 17 (29%) of the subjects tested [107]. The publication of the first case of agammaglobulinemia by Bruton in 1952 [60] demonstrated that the PID diagnosis is first done in the laboratory. However, PIDs require specialized immunological centers for diagnosis and management [33]. A large body of epidemiological evidence supports the hypothesis of the existence of a close etiopathogenetic relation between PID and atopy [73]. In particular, an elevated frequency of asthma, food allergy (FA), atopic dermatitis and enteric pathologies can be found in various PIDs. In addition we will discuss another subject that is certainly of interest: the pseudo-immunodepressed child with recurrent respiratory infections (RRIs), an event that often requires medical intervention and that very often leads to the suspicion that it involves antibody deficiencies [149].

Molecular and functional characterization of a new X-linked chronic granulomatous disease variant (X91+) case with a double missense mutation in the cytosolic gp91phox C-terminal tail

We report here two atypical cases of X-linked CGD patients (first cousins) in which cytochrome b(558) is present at a normal level but is not functional (X91+). The mutations were localized by single-strand conformational polymorphism of reverse transcriptase-polymerase chain reaction amplified fragments and then identified by sequence analysis. They consisted in two base substitutions (C919 to A and C923 to G), changing His303 to Asn and Pro304 to Arg in the cytosolic gp91phox C-terminal tail. Mismatched polymerase chain reaction and genomic DNA sequencing showed that mothers had both wild-type and mutated alleles, confirming that this case was transmitted in an X-linked fashion. A normal amount of FAD was found in neutrophil membranes, both in the X91+ patients and their parents. Epstein-Barr virus-transformed B lymphocytes from the X91+ patients acidified normally upon stimulation with arachidonic acid, indicating that the mutated gp91phox still functioned as a proton channel. A cell-free translocation assay demonstrated that the association of the cytosolic factors p47phox and p67phox with the membrane fraction was strongly disrupted. We concluded that residues 303 and 304 are crucial for the stable assembly of the NADPH oxidase complex and for electron transfer, but not for its proton channel activity.

Genetic analysis of 13 families with X-linked chronic granulomatous disease reveals a low proportion of sporadic patients and a high proportion of sporadic carriers

X-linked chronic granulomatous disease (X-CGD) is the most common type of CGD, whose responsible gene has been identified and termed as CYBB, according to the gp91-phox, a subunit of cytochrome b558. Although approximately 200 different mutations of the gp91-phox gene have been reported, no precise study of the proportion of sporadic cases in X-CGD, based on molecular genetic analysis, has been reported. We made a genetic analysis of six newly identified X-CGD patients together with that of eight previously reported X-CGD patients. The mutations newly detected were three missense mutations, two splice mutations, and one insertion of 2 bases. All of the mutations were novel. Twelve mothers (two of them came from the same family) and four maternal grandmothers from 13 different X-CGD families were available for further genetic studies. It was revealed that a proportion of sporadic patients was low and that of sporadic carriers was high. These results suggest that the mutation for the disease originates mainly from male gametes.

Mutation analysis of five Japanese families with Wiskott-Aldrich syndrome and determination of the family members' carrier status using three different methods

Mutation analysis for five families with Wiskottt-Aldrich syndrome was performed. The mutations found were two missense mutations, two one-base deletion mutations, and a large deletion mutation in the WASP gene. The three mutations had been reported before, but the remaining two were new. We used the mutation information to determine the carrier status of the female relatives of the patients. Three different approaches were taken depending on the type of mutation, and the carrier determination was successfully performed.

A 15-base pair (bp) palindromic insertion associated with a 3-bp deletion in exon 10 of the gp91-phox gene, detected in two patients with X-linked chronic granulomatous disease

Molecular genetic studies were carried out on two maternal cousins with X-linked chronic granulomatous disease (X-CGD). Sequencing analysis of polymerase chain reaction (PCR)-amplified DNA fragments from both patients revealed a 15-base pair (bp) insertion associated with a 3-bp deletion in exon 10 of the cytochrome b heavy chain (gp91-phox) gene. Results of genomic PCR with primers flanking the insertion/deletion site confirmed the mutation, and also demonstrated that their mothers were carriers for the disease. Palindromic sequences were found in the 15-bp insertion as well as in the flanking 3-bp deletion site, which may play a role in the mechanism of this mutation.

Pulmonary aspergillosis and pseudosequestration of the lung in chronic granulomatous disease

We present a case of chronic granulomatous disease with an angiographically proven pseudosequestration of the lung. The patient was a 15-year-old boy who was admitted to the hospital with symptoms of fever, cough, hemoptysis and a subcutaneous abscess. Aspergillus fumigatus was isolated from the sputum and the abscess. During treatment, angiography demonstrated on anomalous blood supply to the right middle lobe. The therapeutic implications of pseudosequestration of the lung for the treatment of chronic granulomatous disease are discussed.

Molecular genetic studies of two families with X-linked chronic granulomatous disease: mutation analysis and definitive determination of carrier status in patients' sisters

Molecular genetic studies of two families with X-linked chronic granulomatous disease (X-CGD) were performed. The patients showed abnormal patterns on Southern blot analysis using cytochrome b heavy chain (CYBB) cDNA as a probe. Both patterns differed and neither has ever been observed in normal individuals. We applied the results to the diagnosis of the carrier state in the patients' sisters. The results clearly demonstrated that each patient's sister possessed the same abnormal allele as the patient's CYBB gene, as detected by Southern analysis. Thus, the results confirm that both of the patients' sisters are carriers of the disease. Further molecular analysis of the patients' mutation revealed that they were a point mutation, and a partial deletion of the CYBB gene, respectively. These mutations have not previously been reported.

A newly recognized point mutation in the cytochrome b558 heavy chain gene replacing alanine57 by glutamic acid, in a patient with cytochrome b positive X-linked chronic granulomatous disease

Molecular genetic analysis was performed in a patient with cytochrome b positive X-linked chronic granulomatous disease. A previous Southern blot study, using a cytochrome b heavy chain cDNA as probe, revealed a Pst I restriction fragment pattern for the cytochrome b heavy chain gene (CYBB) different to that of normal individuals. Since restriction length polymorphism with Pst I has never been observed in control individuals and no abnormal restriction fragment patterns in the patient's CYBB was detected with seven other enzymes used, we focussed on the single Pst I site in the CYBB cDNA as being the only mutation site responsible for his disease. A fragment of the patient's cDNA which included the Pst I site was amplified by reverse polymerase chain reaction, and loss of the Pst I site in the fragment was confirmed by incubation with Pst I. Subsequent sequence analysis of the fragment revealed a point mutation in the Pst I site (cytosine to adenine), substituting glutamic acid for alanine at position 57.

The respiratory burst oxidase and the molecular genetics of chronic granulomatous disease

The phagocyte respiratory burst oxidase plays a central role in the inflammatory response. This membrane-bound enzyme complex is comprised of both integral membrane and cytosolic proteins and catalyzes the formation of large quantities of superoxide in response to inflammatory stimuli. While superoxide and its oxidant derivatives normally serve a microbicidal function, excessive or inappropriate release of these products contribute to inflammatory tissue injury. Chronic granulomatous disease (CGD) is a group of inherited disorders characterized by an absent neutrophil respiratory burst, which leads to recurrent and often life-threatening infections in affected patients. The analysis of the specific cellular defects in CGD has been instrumental in the identification and characterization of individual oxidase components. Four distinct genetic subgroups are presently recognized, each involving a different protein essential for respiratory burst oxidase function. This article summarizes recent advances in the characterization of the protein components and cellular biochemistry of the respiratory burst oxidase and reviews the classification and molecular genetics of CGD. The application of these findings to new approaches to the diagnosis and treatment of CGD are also reviewed.