The Evaluation of Dihydrorhodamine 123 Assay in Chronic Granulomatous Disease

Abstract

Reply: The letter by Köker is correct in pointing out that not all patients with autosomal recessive Chronic Granulomatous Disease (CGD) have a broad intermediated Dihydrorhodamine (DHR) stimulated pattern like that depicted in Figure 1 in the article by Bender et al (Pediat Inf Dis J. 2000;28:529–533). We did not mean to infer that all of the AR forms of CGD were associated with this broad pattern. In our experience, however, when autosomal cases present later in life, with less severe infections, and especially those with the p47-phox form of the disorder, there is often a broad intermediate pattern such as that depicted, which is easily confused with variant X-linked CGD. In fact, the broad intermediate DHR pattern shown came from a previously healthy 8-year-old female admitted with pneumonia due to Chryseomonas luteola. Her older sister, at 12 years of age, had a similar DHR pattern but had never suffered a serious infection. One of the main points of our paper was to suggest that determining the mother's DHR pattern is often useful in distinguishing between X-linked and AR disease. As pointed out by Köker, nonrandom inactivation of the good X chromosome in a female X-linked carrier can occur resulting in very little to no respiratory burst in the female, which can even lead to clinical disease. The author is correct in stating that some AR cases including those with p47, p67 and p22 abnormalities may show patterns like that of classic X-linked disease. We have personally observed complete absence of respiratory burst activity in females with p67 phox and p22 light chain of cytochrome b558 associated mutations. Lastly, CYBB mutation nomenclature can be difficult because the CYBB database (starting at the beginning of exon 1) is numbered differently than HUGO nomenclature (starting at the ATG initiation site). Patient 2 is listed as c.266G>A in the manuscript and CYBB database (http://bioinf.uta.fi/CYBBbas), but the HUGO nomenclature is c.252G>A. It is a point mutation at the end of exon 3 (A84A) leading to a splice donor defect. The same 14 base difference explains the difference between c.744T>A (manuscript and database) versus c.730T>A (HUGO). Harry R. Hill, MD Carl T. Wittwer, MD, PhD Departments of Pathology, Pediatrics, and Medicine University of Utah School of Medicine Salt Lake City, UT