Chronic granulomatous disease may be an underlying cause for invasive nocardiosis.

Sir,

We read with interest the paper by Singh et al. on their 5-year experience of managing pulmonary nocardiosis among obvious immunosuppressed patients (retrovirus infection, drug-induced, and solid-organ transplantation) and also in younger patients but where phagocytic abnormalities were not excluded/reported.[1] The most common symptomatic phagocytic defect is chronic granulomatous disease (CGD) where there is a profound reduction in superoxide generation by phagocytes (neutrophils, eosinophils, monocytes, and macrophages) leading to defective intracellular killing of mainly Staphylococcus aureus and Aspergillus species including Burkholderia, Serratia, and Nocardia. CGD is now known to be caused by mutations in genes encoding protein subunits of the nicotinamide adenine dinucleotide phosphate oxidase complex and inherited in either X-linked recessive (gp91) or autosomal recessive pattern (p47, p67, and p22). The diagnosis can be made with the screening nitroblue tetrazolium dye reduction test or the more accurate dihydrorhodamine assay using flow cytometry and confirmed with genetic studies/superoxide generation. Suppurative lymphadenitis with cutaneous abscesses (cold abscesses) leading to granuloma formation, hepatic abscesses, lung infections, and diarrhea constitute the most common presentations in patients with CGD.[2] Therefore, infections (recurrent or severe) with any of the above-mentioned organisms warrant a screen for CGD in such patients.

Data from the National Institutes of Health (NIH), Bethesda, showed calculated incidence rates (between 1969 and 2012) of Nocardia infections in 268 patients with confirmed diagnoses of CGD at 0.81/100 patient-years.[3] Fungal infection accounted for 21 deaths (21/38 [55%]), when determined by both incidence and mortality, and was worse in the gp91 cohort. Overall Aspergillus-specific mortality was 9%, whereas there was only 1 death due to Nocardia infection in an X-linked patient. Staphylococcus infections were higher overall in those patients who died and were independent of genotype. Even then, fungal infections had a higher risk of mortality than bacterial infections (P = 0.03), and mortality rates were higher among those who had fungal infections than in those who did not (relative risk 1.8 [95% confidence interval, 1.06–3.06]). Previous data from NIH (2002 publication) reported the frequency of disseminated nocardiosis in CGD at 25% (28 episodes of Nocardia infection all of which were pulmonary infection, n = 23) with double the frequency of nocardiosis (56%) in patients receiving neither interferon-gamma (IFNγ) nor sulfonamide prophylaxis.[4]

In tuberculosis (TB)-endemic countries, especially extensively drug-resistant TB, causes of chronic infections are often overlooked by physicians. Children who present with invasive aspergillosis and TB may have CGD as reported recently from Pakistan.[5] In general, X-linked patients have more severe disease, especially in those with lower residual superoxide production.[3] Antibiotic (trimethoprim-sulfamethoxazole), antifungal (itraconazole, voriconazole) prophylaxis are the mainstay of treatment and immunomodulation with IFNγ reduces frequency and severity of infections. As invasive or severe infections continue to occur throughout life in these patients, it is important that we exclude CGD as a cause of pulmonary nocardiosis, especially in those where CD3+/CD4+ T-cell absolute counts and serum immunoglobulin levels are within normal reference ranges.

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