*Corresponding author:
Dr Ankur Kumar Jindal,
Assistant Professor- Pediatric Allergy Immunology Unit, Advanced Pediatrics Centre, Department of Pediatrics, Post Graduate Institute of Medical Education and Research, Chandigarh, India- 160012
Email: ankurjindal11@gmail.com
Ph: +91-95920-65559
Word Count: 1000 (approx.)
Table: 1
Figure: 1
Supplementary figure: 2
Sources of funding: Funded by Indian Council of Medical Research (Id 2020-9482)
Conflicts of interest: All authors declare there are no conflicts of interest
Informed consent:   Written informed consent was obtained from parents of children included in this study for publication as clinical image
Consent for publication:  All authors have given final approval for publication
Competing interests:  None
Author contributions: AS, SB, JD, PV, DS and AKJ were actively involved in the diagnosis and management of this case. JD, AKJ and SS were involved in the immunological tests and microbiological tests done in this child and interpreted the results of those tests. AS and SB wrote the manuscript. AKJ and AS edited the manuscript. AKJ supervised the entire manuscript preparation.
Disseminated Mycobacterium fortuitum infection in a young girl withIFN-γR1defect masquerading as histiocytosis
Archan Sil, Suprit Basu, Jhumki Das, Sunil Sethi, Debajyoti Chatterjee, Vignesh P, Deepti Suri, Ankur Kumar Jindal*
To the Editor,
Mendelian susceptibility to mycobacterial disease (MSMD) is a rare inborn error of immunity (IEI) of interferon-γ (IFN- γ) and interleukin 12-23 (IL12-23) pathway with predisposition to weakly virulent mycobacterial infections (Mycobacterium bovis and environmental non-tuberculous mycobacteria) and intra-macrophagic organisms like bacteria (typhoidal and non-typhoidal Salmonella, Listeria, Klebsiella etc.), fungus (Histoplasmosis, coccidiomycosis, paracoccidiomycosis, candida) and parasites (toxoplasma, leishmania) (1). While Bacille Calmette-Guérin (BCG) vaccine related complications were initially reported in 1951, first gene associated with MSMD (IFNγR1 defect) was discovered in 1996 (2). Till date, 18 different gene defects and 250 mutations have been reported in patients with MSMD (IL12Rβ1 defect is the most common) (2).
Clinical manifestations may vary from early onset, fatal, disseminated mycobacterial disease to late onset, localized, less severe mycobacterial infection that may remain clinically silent for long duration (1,2). This variation in clinical presentation depends on the specific gene involved and can be explained by incomplete penetrance. Clinical spectrum of MSMD can be divided into two main classes- (1) Isolated MSMD (mycobacterial infection as the predominant manifestation) and (2) Syndromic MSMD (presence of mycobacterial as well as non-mycobacterial infections) (2). In countries where tuberculosis is endemic, suspicion and diagnosis of MSMD has far reaching effects (1). Unrestrained infection at times can lead to atypical manifestations such as macrophage activation syndrome or vasculitis (1). Although uncontrolled mycobacterial infection and abnormal T cell function can act as triggers for hemophagocytic lymphohistiocytosis, it is considered as an uncommon presentation of MSMD (3). A predominant histiocytosis like presentation because of chronic mycobacterium infection has rarely been reported in children with MSMD (4). This may create a diagnostic conundrum form the treating physician. Herein, we report one such case.
A 3-year-old girl presented with abdominal distension for 1-year along with multiple neck swellings, intermittent fever and progressive pallor for 3 months. She was given anti-tubercular treatment for 3 months prior to coming to us. Her elder brother had died at the age of 3 months due to pneumonia. However, his medical records could not be retrieved.
On examination, she had pallor, generalized lymphadenopathy, eczematous skin rashes, tachypnea and spleno-hepatomegaly (spleen reaching nearly up to umbilicus). Laboratory investigations showed anemia and thrombocytopenia with elevated inflammatory markers[Table 1] . Infective work up including tuberculosis, kala-azar, cytomegalovirus and HIV came negative. Serum beta-D glucan was within normal limits [Table 1] . Contrast enhanced computed tomography showed patchy consolidation with ground glass opacities in dependent region of both lungs. Fine needle aspiration cytology from lymph node showed granulomatous inflammation and acid-fast bacilli (AFB) stain was negative. Immunological work up showed decreased proportion of naïve helper (CD3+CD4+CD45RA+) and cytotoxic T lymphocytes (CD3+CD8+CD45RA+) and increased proportion of memory helper T lymphocytes (CD3+ CD4+CD45RO+). Lymph node biopsy and bone marrow biopsy showed infiltration of mixed histiocytic population without any evidence of malignancy suggesting a possibility of a histiocytic disorder (Figure 1) . However, negative CD1a and S-100 stain ruled out Langerhans cell histiocytosis (LCH).
She was initially treated with broad spectrum antimicrobials. However, she continued to have eczematous skin lesions and frequent blood transfusion requirements. Considering a clinical possibility of non-LCH histiocytic disorder, she was initiated on oral prednisolone (2 mg/kg/day) and whole exome sequencing was sent. She showed a brisk clinical response, her rashes subsided and her transfusion requirements reduced.
Whole exome sequencing revealed a homozygous c.201-2A>G splice variant in intron 2 of IFN-γR1 gene. This splice variant skips from end of exon 2 to middle of exon 3 and omit bases 201–302. The observed variation has previously been reported in patients with nontuberculous mycobacterial infections with MSMD. Flow-cytometry showed reduced expression of phospho STAT-1 (Supplementary Figure 1)and phospho STAT-4 on gated monocytes and decreased IFN-γ receptor 1 expression on activated granulocytes and monocytes(Supplementary Figure 2) in the index child compared to control. She was diagnosed to have MSMD and was empirically initiated on anti-tubercular treatment (isoniazid, rifampicin, levofloxacin and ethambutol). Oral prednisolone was gradually tapered and discontinued.
Four months later, she had recurrence of fever, skin rash and size of liver and spleen increased. A lymph node biopsy was repeated from the axilla which grew Mycobacterium fortuitum . She was initiated on meropenem, amikacin, cefixime, clofazimine and levoflocxacin as per drug sensitivity pattern. Due to sub-optimal response, she was subsequently initiated on 3 million units of subcutaneous interferon-α (IFN-α) thrice weekly. On follow-up, regression of hepatosplenomegaly and improvement in cytopenia were noted. She is presently being evaluated for hematopoietic stem cell transplantation.
Uncontrolled activation of macrophages and natural killer (NK) cells cause increased production of pro-inflammatory cytokines. This leads to a state of immune dysregulation that affects multiple systems presenting as sub-acute to chronic febrile illness, eczematous rashes, generalized lymphadenopathy, hepatosplenomegaly, pulmonary infiltrations, and lytic bony lesions. Pancytopenia, hyperferritinemia, hypertriglyceridemia and hypofibrinogenemia reflect this hyperinflammatory state (3). Index child had similar multisystemic involvement which made us consider possibilities of histiocytic disorders and initiation of corticosteroids was considered. However, whole exome sequencing suggested a diagnosis of MSMD and subsequently M. fortuitum was also isolated form the lymph node biopsy. Histiocytic presentation of MSMD has rarely been reported in literature in patients with both IL-12Rβ1 andIFN-γR1 defects (3,4).
Environmental non-tuberculous mycobacteria are one of the signature organisms associated with MSMD. Index child showed growth of M. fortuitum from lymph node biopsy. M. fortuitum has been previously reported on multiple occasions in patients with completeIFN-γR1 deficiency (5). Most reported patients of MSMD withM. fortuitum infection are from Turkey, Italy, Greece and Spain. Some of them had associated co-infections with non-typhoidalSalmonella or M. tuberculosis . Three of them underwent HSCT and 2 of them succumbed to the illness (5). Cephalosporine (cefoxitin, cefixime), aminoglycosides (amikacin, gentamycin) and fluroquinolones (ciprofloxacin, levofloxacin) are used as empiric treatment for M. fortuitum . The index child was, however, treated with meropenem, levofloxacin, amikacin, clofazimine and cefixime based on sensitivity pattern.
Interferon alpha has been found to be useful in patients with MSMD who have refractory mycobacterium infection as was also seen in the index case (6). She is presently being evaluated for HSCT.
To conclude, MSMD should be considered in patients with unexplained histiocytic disorders. All attempts should be made to identify mycobacteria in these cases so that targeted therapy can be used. Interferon alpha may be used in patients with IFN-γR1 defect to control mycobacterium infection.