History: A 3-month-old girl, product of 3rd degree consanguineous marriage presented with history of generalized, erythematous, maculopapular rash all over body that developed at one month of age. Rash was associated with skin peeling and it resolved spontaneously in one month. She subsequently had progressive loss of scalp hair and eyebrows. She also had bilateral purulent ear discharge since the age of 2 months associated with cough, respiratory distress and loose stools. Child was admitted twice for these complaints in a nearby hospital and was managed with IV antimicrobials. She had received BCG vaccination at 1 month of age, however, she developed no reaction at the BCG site.

Clinical examination: She had tachycardia (heart rate 150/minute), tachypnea (respiratory rate-62/minute), pallor, alopecia with loss of eyebrows (Fig. 1), skin peeling in the left axilla, no BCG scar, coarse crepitation in bilateral chest and hepato-splenomegaly. Initial clinical possibilities were Human Immunodeficiency Virus (HIV) infection, Severe Combined Immunodeficiency (SCID) with maternal engraftment, congenital Cytomegalovirus (CMV) infection and Langerhans cell histiocytosis.

(a)	(b)
Fig. 1 Alopecia over left fronto-parietal region and loss of eyebrows (arrows) (a); chest X-ray (anteroposterior view) showing interstitial pattern of infiltrates in both lungs, predominantly perihilar. Homogenous opacity in right upper lung fields and absent thymic shadow (b).

Immunological investigations (Table I): She had undetectable IgG and IgA and normal IgM; nitroblue tetrazolium (NBT) dye reduction test and dihydrorhodamine 123 (DHR) assay were normal; lymphocytes subsets showed reduced CD3+ T cells (32% of all lymphocytes), normal CD19+ B cells (29% of all lymphocytes) and normal CD56+ NK cells (39% of all lymphocytes); CD 127 (IL-7Rá) expression was reduced (Web Fig.1a and 1b); CD45RA expression on CD3+T cells and CD8+T cell was reduced suggestive of low naïve T cells; CD45RO expression on CD3+T cells and CD8+T cells was elevated suggestive of increased memory T cells (likely to be of maternal origin).

TABLE I Laboratory Investigations of Index Case

Unit’s final diagnosis: Severe combined immunodeficiency (T-B+NK+) with IL-7R alpha deficiency with maternal engraftment, severe pneumonia, sepsis, septic shock and pulmonary hemorrhage.

Case analysis can be discussed with respect to the underlying disease; the etiology for pneumonia; the cause for Intussusception; and the terminal events.

The clinical presentation is suggestive of an underlying immune defect. After ruling out HIV infection, the most likely underlying diagnosis is SCID, as she was born to a consanguineously married couple and presented within the first 2 months of age with severe pneumonia, otitis media, alopecia (likely due to maternal engraftment), and absence of BCG scar. Laboratory investigations revealed lymphopenia, hypogamma-globulinemia, low CD3+ T cells, naïve T cells and absence of thymic shadow on chest X-ray. She fulfills the European society of immunodeficiency (ESID) registry working definition for clinical diagnosis of SCID.

She had features of maternal engraftment (i.e. presence of maternal T lymphocytes in the circulation leading to manifestations that are like graft versus host disease). Most common manifestation of maternal engraftment is skin involvement with eczema, erythema, alopecia and skin peeling; followed by liver involvement (with mild to moderate elevation of liver enzymes) and gastrointestinal tract involvement (diarrhea). Index child has history of generalized erythema and peeling of skin and alopecia. She also had elevated liver enzymes.

The etiology for pneumonia is likely to be polymicrobial. Invasive fungal infection can be considered in view of positive serum galactomannan index, CMV can be considered in view of positive CMV DNA PCR in the blood and suggestive radiological findings. Pneumocystis jiroveci pneumonia can also be considered in view of radiological findings. As she received BCG vaccination, so a possibility of disseminated BCG infection with pneumonia can also be considered.

She also had intussusception as evident on ultrasound of the abdomen. The intussusception in this age group would most likely be related to infections which could be a viral or bacterial infection. In the index child, Mycobacterium bovis and CMV can be considered. BCG infection leading to recurrent intussusception has previously been reported in SCID [2].

The cascade of terminal event can be summarized as SCID leading to severe pneumonia and polymicrobial sepsis that has led to multiorgan dysfunction and pulmonary hemorrhage finally causing shock and death.

Senior resident of the treating unit: The diagnosis of SCID is not in doubt here and other differentials diagnosis that were considered can easily be excluded based on the immunological investigations. I expect severe depletion of T cells in the thymus; changes of GVHD in skin and gut and CMV or Mycobacterium bovis in lungs and gastrointestinal tract.

Physician 1: Was fundus checked in the index case to look for evidence of CMV retinitis?

Senior resident of the treating unit: The fundus evaluation was done and there was no evidence of CMV retinitis.

Pediatrician 1: Mycobacterium bovis infection secondary to BCG vaccination often produces skin lesions and fine needle aspiration from these skin lesions can yield acid fast bacilli (AFB). However, there were no skin lesion in the index child. Gastric lavage for AFB was negative. However, it is not always necessary to find AFB on gastric lavage. Index child had alopecia and loss of eyebrows that was suggestive of maternal engraftment or Omenn syndrome.

Pediatrician 2: The syndrome of SCID should be suspected if the child presents within the first few months of life with rash and polymicrobial sepsis which is not responding to antimicrobials. If hemogram shows lymphopenia as in the index child, SCID should be considered. The phenotype of SCID can be evaluated with the help of flow cytometry. Index child had an unusual phenotype i.e. T-B+NK+.

A complete autopsy was performed on this 3-month-old girl. The peritoneal cavity revealed ascites with 270 mL of straw-colored fluid. The other serous cavities were within normal limits.

Thymus weighed 2 g (normal weight for this age is 3 g) and revealed maintained lobular architecture on gross examination. However, on microscopy cortico-medullary distinction was lost and there was absence of Hassall’s corpuscle. These features are consistent with thymic dysplasia. CD3 immunostain revealed reduction in T-lymphocytes, however, the thymocytes were preserved as highlighted by pan-cytokeratin (Web Fig. 2 a-d).

All sampled lymph nodes showed depletion of lymphoid population. T cell zones i.e. paracortical and interfollicular regions showed reduction in T lymphocytes as highlighted by CD3. CD20 performed revealed normal population of B lymphocytes (Web Fig. 2e-g). Peyer’s patches were hypertrophic with relative preservation of B cell zone (Web Fig. 2h). However, there was marked reduction of T cell zone. Spleen weighed 20 g (normal for this age is 25 g). On histology, there was mild congestion of the red pulp with preservation of B cell zone and relative reduction of periarteriolar T cell zone.

Both the lungs were heavy (weight 250 g) with dull pleural surface. Many subpleural nodules were identified. The cut surface showed diffuse areas of hemorrhagic consolidation in all the lobes, bilaterally. Tracheo-bronchial tree was unremarkable. Microscopically, there was interstitial widening with mild lymphomononuclear infiltrate along with many large cells protruding into the alveolar lumen. Many cytomegalovirus inclusions (CMV) were noted within alveolar pneumocytes and endothelial cells. These cells demonstrated nucleomegaly along with presence of basophilic to amphophilic inclusions in the nucleus and a perinuclear halo (Web Fig. 2i). Immunostaining for CMV revealed the burden of infection. Similar inclusions were also noted in the bronchial epithelial cells and endothelial cells of blood vessels. Adjacent areas of lung parenchyma showed diffuse alveolar hemorrhages and focal hyaline membrane formation. No granulomas were identified and Ziehl-Neelsen stain for acid fast bacilli (AFB) was negative. PAS stain performed did not reveal any fungal hyphae and gram’s stain performed did not reveal any micro-organisms.

Adrenals examined showed foci of necrosis with the presence of CMV inclusions within the necrotic foci. Heart (weight 30 g) was unremarkable grossly. However, few endothelial cells with the interstitial vessels in the myocardium showed presence of CMV inclusion which was confirmed on immunohistochemistry. Liver (weight 450 g) was unremarkable on gross examination. Cut surface was pale yellow to greasy in appearance. On microscopy, diffuse macrovesicular steatosis predominantly involving the zone 1 and zone 2 areas with relative preservation of zone 3 hepatocytes was noted. Few scattered CMV inclusions were also noted in the Kupffer cells of the sinusoids which was confirmed on immunohistochemistry. Rest of the organs including brain, kidneys, bone marrow, stomach, esophagus, skin, thyroid, skeletal muscle were unremarkable grossly and microscopically.

Final autopsy diagnosis:

Senior resident of the treating unit: There is perfect correlation between flow cytometry reports and pathology findings in lymph nodes. B cells were present in the flow cytometry report and were also found in the lymph nodes. In many types of SCID, the B cells are absent in blood and there we see depletion of B cell zone in the lymph nodes. Was any organism isolated at the site of intussusception?

Pathologist 1: No organism was seen at the site of intussusception. The intussusception was likely due to hyperplasia of Peyer’s patches.

Physician 1: Was flow cytometry analysis done for the parent’s sample and were parents counselled about future pregnancies.

Senior resident of the treating unit: Flow cytometry analysis of parent’s sample is not usually done in cases of SCID. Molecular analysis will be done for both child and parents. Parents have been advised to avoid further pregnancy till the genetic confirmation, following which a prenatal diagnosis will be offered.

Pediatrician 3: This is an autosomal recessive SCID and parents are likely to be the carriers. So, flow cytometry is not useful in diagnosing carrier status which can only be diagnosed with molecular analysis.

Pathologist 2: In the year 1980s, these types of cases did not fit into any clinical diagnosis, these infants will have infections like CMV, PCP with hypogammaglobulinemia and lymphopenia. However, the level of investigations was not as extensive as they are now. One thing that was pursued extensively at that time was the possibility of AIDS. Extensive investigations were done on thymus and lymphoid system. Serial sections of thymus were done which demonstrated isolated Hassall’s corpuscles and normal blood vessels. In thymic dysplasia thymus are abnormally small with small blood vessels, lobules are shrunken and no lymphoid tissue in cortex and medulla which are classical of SCID.

Pathologist 1: Lymphoid cells in the thymus were due to maternal engraftment and it is difficult to differentiate lymphoid cells from maternal origin or from the child. CMV infection is most likely acquired as the major bulk of CMV disease was in lung and not in liver.

In almost all subtypes of SCID, thymus is usually atrophic [8] and poorly visualized on a chest radiograph [9] as was seen in the index patient also. The histopathology of thymus in SCID demonstrates depletion of lymphocytes and lack of differentiation of thymic epithelium. Poor differentiation of thymic epithelium is responsible for the absence of Hassall’s corpuscles and is on one of the most important histopathological feature of SCID [10]. Thymic epithelium has very important role in the normal differentiation of T-cell population and due to thymic dysplasia in SCID, T-cell differentiation is impaired [11].

Intussusception can have variable etiology (i.e. viral, bacterial or protozoal infections and benign or malignant tumors). As compared to adults in whom a definite lead point is often found, it is rather uncommon to find a cause in children. Hyperplasia of Peyer’s patches may be seen in upto a third cases of idiopathic intussusception [12]. Index patient also had similar pathology at the site of intussusception.

Contributors: PR: pathology protocol presentation, writing of manuscript, review of literature; DL: clinical protocol presentation, writing of manuscript, review of literature; AKJ: clinical protocol presentation, writing of manuscript, editing of manuscript, review of literature, patient management; KG: pathology protocol presentation, review of literature, editing and final approval of manuscript; AR: laboratory investigations, review of literature, editing and final approval of manuscript.

Discussants: Clinical discussant and Pediatrician 1: Devika Laishram; Senior resident of treating unit: Ankur Kumar Jindal; Pathologist 1: Poojitha Reddy; Pathologist 2: Kirti Gupta; Pediatrician 2: Amit Rawat; Pediatrician 3: Surjit Singh.

Funding: None; Competing interest: None stated.

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