Tuberculosis, onychomycosis and immune deficiency in complicated Crohn’s disease

Abstract

The immune system is composed of innate humoral defence and adaptive immunity. One of the key mechanisms of the innate humoral defence is through complement activation. Mutations of certain enzyme may affect the complement activation and result in decreased defence against microorganisms. Mannan-binding lectin serine protease 2 (MASP-2) mutation was associated with recurrent infections and autoimmune diseases. Tuberculosis (TB) has been linked with mannose-binding lectin and MASP-2 gene polymorphism. We report a case of a paediatric patient with MASP-2 deficiency with classical and atypical features associated with Crohn’s, onychomycosis and severe cutaneous infections including TB. We also report the presence of a new mutation variant in MASP-2 reported in whole exome sequencing of our patient.

Background

Inflammatory bowel diseases (IBDs) include Crohn’s disease (CD), ulcerative colitis and unclassified inflammatory bowel diseases. CD among paediatrics is different from adults.¹ The cause of CD and the reason for paediatric onset is different from adult onset and remains unknown despite extensive research, and a multifactorial aetiology has been suggested. In contrast to adult-onset IBD, paediatric-onset IBD often shows extensive disease and rapid progression requiring early immunomodulatory therapy.^{2 3}

The latest global incidence of paediatric-onset IBD is found to be variable ranging from 0.1 to 13.9 cases in 100 000.⁴ In Saudi Arabia, the incidence of IBD was reported during 1993 to 2012, and CD rate was found to be 0.3 in 100 000.^{5 6} We looked into the association between Crohn’s with diseases the patient had including onychomycosis, mannan-binding lectin serine protease 2 (MASP-2) deficiency, tuberculosis (TB) and allergic conjunctivitis. IBD is frequently associated with extra-intestinal manifestations which involve the joints, the skin and the eyes.⁷ Onychomycosis affects all paediatric age groups but it is uncommonly seen among paediatric-onset IBD.^{8 9} The immune system is composed of innate humoral defence and adaptive immunity. One of the key mechanisms of the innate humoral defence is through complement activation. Studies showed that MASP-2 deficiency, one of key elements in complement pathway activation in innate immunity, was related to some autoimmune diseases, low immune defences and recurrent infections. Also, high levels of mannan-binding lectin were associated with increased number of TB patients.^{10 11} Analysing protein coding genes using whole exome sequencing may be an efficient method to diagnose those genetic abnormalities.¹² Our patient lives in a TB-endemic region, which may have predisposed to the infection. Makkah region, where our patient currently lives, had the highest incidence rates of TB in the country, Saudi Arabia.¹³ A case-control study was conducted where 503 patients with TB and 419 healthy controls were recruited and tested for gene polymorphism. The MASP-2 was significantly associated (p<0.05) with the susceptibility of TB. MASP-2 was reported to have many types. New subvariants of the gene are being discovered, and those variations may influence the patient’s susceptibility to infections, metabolic and autoimmune diseases.^{14 15} We reported a case of a 11-year-old boy with a new variant of MASP-2 immunodeficiency who developed complicated CD, onychomycosis, allergic conjunctivitis and multiple eye and skin infections including the recently treated TB lymphangitis.

Case presentation

An 11-year-old boy with CD presented in May 2017 with 4 weeks of worsening abdominal pain, fever, night sweating and a lump in the thigh. The pain was primarily in the right lower quadrant, waxing and waning in nature and described as ‘cramping’. The patient did not have history of any known allergies. Family and social history was unremarkable. The patient lives with his parents in Makkah region in the Western side of Saudi Arabia, a known endemic area with TB.

He was diagnosed with CD in 2010, and he had a complicated colitis with terminal ileitis due to poor response to medical treatment (steroids, azathioprine and infliximab). The infliximab failure was caused due to development of infliximab antibodies in spite of normal infliximab levels. Due to the infliximab antibodies and severe disease at early onset IBD, infliximab was switched to adalimumab. He received adalimumab injection 20 mg subcutaneously one injection every 2 weeks for 12 months duration with dramatic response in his symptoms. He did not have TB prior to receiving adalimumab. Quantiferon-TB test and Brucella serologies were done, and the results came negative. He was prescribed adalimumab 40 mg subcutaneously taken once every 2 weeks.

In November 2011, the patient had undergone pancolectomy with ileal pouch-anal anastomosis and ileostomy stoma. Post surgery, he was kept on 5-aminosalicylic acid in remission for 1 year. In December 2012, he developed recurrent cutaneous abscesses treated by antibiotics. The last abscess was severe in the thigh, which was treated by incision and drainage. Three months later, he developed white and yellow nails discolouration associated with thickening of the nails (see figure 1). These nails changes confirm diagnosis of onychomycosis. Our patient also had a history of severe recurrent eye infections and allergic conjunctivitis. He is on treatment and follow-up with ophthalmology. He was taking ophthalmic olopatadine and fluorometholone acetate solutions.

Figure 1.

Total onychomycosis: white discolouration of the proximal nail plate which is completely invaded by fungi and friable associated with subungual hyperkeratosis.

In April 2015, he suffered from recurrent abdominal pain, watery stoma output and decreased activity. Ileoscopy showed multiple ulcerations in the ileum. Histopathology revealed chronic active inflammations. In February 2016, his chronological age was 10 years and 9 months while the bone age was 9 years according to Pyle and Greulich standards for skeletal development. The SD is 10.5 months (see figure 2). The patient’s growth velocity was inadequately 2.6 cm in 5 months duration. Paediatric endocrinologist prescribed human growth hormone (5 mg/1.5 mL) syringe 0.67 mg subcutaneously 10 clicks daily 6 days/week.

Figure 2.

Left PA hand and wrist bone age history: an 11-year-old male known IBD patient with pancolectomy presented with short stature. Findings: the chronological age of this child is 10 years and 9 months. The estimated bone age is 9 years according to Pyle and Greulich standards for skeletal development. The SD is 10.5 months. IBD, inflammatory bowel disease.

Investigations

Physical examination revealed severe growth retardation and short stature. Abdominal examination revealed no hepatosplenomegaly or ascites. The right upper thigh mass was noted with redness and hotness. It measured 3×4 cm. It was fluctuated with smooth surface without discharge. Right posterior cervical lymph node is enlarged, erythematous and measured 2×2 cm. Other systemic examination was otherwise unremarkable.

Lab investigations were sent. Complete blood count showed slightly increased white blood cell count of 12.8×10³ cells/mcL and elevated C-reactive protein (see table 1). Additionally, Inguinal lymph nodes in the thigh were excised, and biopsy was positive for Ziehl–Nielsen stain. PCR of the tissue was positive for mycobacteria species. The diagnosis of TB lymphadenitis was confirmed.

Table 1.

Laboratory findings

Test	Results	Normal ranges
Calprotectin	463 μg/g previously 488 μg/g	≤50 μg/g
CRP	32.1 mg/L	0.0–5.0 mg/L
ALT	13 units/L	9–24 units/L
AST	34 units/L	14–35 IU/L
Bili T	1.9 µmol/L	1.7–11.9 µmol/L
Alk Phos	98 IU/L	127–517 IU/L
Albumin	29 g/L	41–48 g/L
GGT	39 units/L	7–21 IU/L
WBC	12.8×103 cells/mcL	4–11×103 cells/mcL
Hgb	12.0 g/dL	13–18 g/dL
Hct	36.3%	40%–54%
Platelet	462×103 cells/mcL	150–450×103 cells/mcL
PT	14 s	11–14 s
INR	1.2	0.8–1.1
PTT	35 s	25–35 s

ALT, alanine transaminase; AST, aspartate transaminase; Bili T, bilirubin test; CRP, C-reactive protein; GGT, gamma-glutamyl-transferase; Hct, haematocrit; Hgb, haemoglobin; INR, international normalised ratio; PT, prothrombin time; PTT, partial thromboplastin time; WBC, white blood cell.

As his very early onset of Cohn’s disease was complicated by skin abscesses, TB and onychomycosis, a whole exome sequencing was needed. We wanted to investigate whether the patient has a genetic syndrome that may predispose to immunodeficiency and subsequent recurrent infections he had. In October 2016, a sample was sent for whole exome sequencing, which revealed complex heterozygous mutations on MASP-2. The test detected a heterozygous variant in the MASP-2 gene, c.741+1G>A; Chr1(GRCh37):g.11103395C>T. Software analyses (Alamut V.2.7.1) predicted a likely effect on splicing. This variant was also detected in the mother in a heterozygous state. The report stated that this is the first time they detect this variant and it is so far not listed in CentoMD 3.2. It is classified as likely pathogenic (class 2) according to the recommendations of Centogene and Annual Clinical Genetics Meeting.

Treatment

Adalimumab was discontinued and anti-TB was prescribed. He received four-drug regimen: isoniazid, rifampin, pyrazinamide and ethambutol for 9 months duration.

Outcome and follow-up

On follow-up, the patient tolerated anti-TB medications. At 12 months follow-up from the onset of TB, he started to improve. He was completely asymptomatic, and other laboratory investigations normalised. For example, white cell count improved to 6.2×10⁹ /L, calprotectin level reduced to <30, albumin improved slightly reaching 38 g/L (see table 2).

Table 2.

Laboratory findings after 12 months of treatment and regular follow-ups

Test	Results	Normal ranges
Calprotectin	<30 μg/g	≤50 μg/g
CRP	1.2 mg/L	0.0–5.0 mg/L
ALT	26 units/L	9–24 units/L
AST	26 units/L	14–35 IU/L
Bili T	2.7 µmol/L	1.7–11.9 µmol/L
Alk Phos	198 IU/L	127–517 IU/L
Albumin	38 g/L	41–48 g/L
GGT	25 units/L	7–21 IU/L
WBC	6.2×109 /L	4–11×109 /L
Hgb	116 g/L	130–180 g/L
Hct	37.1%	40%–54%
Platelet	510×109 /L	150–450×109 /L

AST, aspartate transaminase; Bili T, bilirubin test; CRP, C-reactive protein; GGT, gamma-glutamyl-transferase; Hct, haematocrit; Hgb, haemoglobin; WBC, white blood cell.

Discussion

We did a literature search using relevant key terms including, MASP-2, TB, CD and onychomycosis. New subvariants of the gene have been discovered and those variations may have influence on patient’s susceptibility to infections, metabolic and autoimmune diseases.¹⁵ Our case is interesting because the patient had a newly identified likely pathologic genetic variant of the MASP-2, based on the whole exome sequencing report. It could have played a role in explaining the disease pathology. Additionally, the patient had onychomycosis associated with his IBD which was unusual for his age.⁸ To our knowledge, there are no cases published of paediatric-onset CD with this combination of severe features including TB and onychomycosis which may support our theory that the new variant MASP-2 our patient has may have contributed to the development of the disease. We think that our patient could have developed onychomycosis due to the presence of variant of the MASP-2 gene.

Learning points.

• Crohn’s disease (CD) may vary in severity among patients. A clinician should be aware of the treatment failure in infliximab. Some patients may develop resistance to treatment in the form of antibody production.

• Tuberculosis screening is crucial in patients with CD prior to treatment with immunosuppressive medications such as adalimumab, especially in TB-endemic countries.

• Understanding of the genetic contribution on younger children gives us a useful insight into the pathogenesis and potential future therapeutic targets in inflammatory bowel disease (IBD).

• Certain gene mutations such as MASP2 were associated with immune system malfunction and emergence of autoimmune diseases such as IBD.

• Whole exome sequencing, a genetic test, was a necessary diagnostic tool that was considered an efficient way to identify the underlying cause of a disease.