Hemophagocytic syndrome secondary to cytomegalovirus infection in an infant.

Virus associated hemophagocytic syndrome is a non-neoplastic, generalized histiocytic proliferation with prominent hemophagocytosis associated with a systemic viral infection. We report a case of cytomegalovirus (CMV) associated hemophagocytic syndrome in a 2 month old male child presenting with rashes, fever, hepatosplenomegaly, cervical lymphadenopathy and pancytopenia. Fine needle aspiration cytology and biopsy from cervical lymph nodes revealed prominent hemophagocytosis. Serology for CMV IgM was positive in both the mother and the child, suggesting recent infection. Possibly there was intrauterine transmission of the infection.

Introduction

Hemophagocytic lymphohistiocytosis (HLH) is a disorder of the mononuclear phagocytic system characterized by proliferation of histiocytes and macrophages, exhibiting phagocytosis of erythrocytes, leucocytes, platelets and their precursors.[12] The hemophagocytic syndrome (HPS), more precisely known as HLH, was first described in 1939.[3] HLH comprises primary HLH (familial/hereditary HLH) and secondary HLH. Secondary HLH could be due to infections, rheumatic disease and malignancies. Secondary HLH is designated as reactive hemophagocytic syndrome.[4]

We present a case of cytomegalovirus-associated hemophagocytic syndrome (CMV-AHS) in a 2 month- old child acquired from the mother by vertical transmission.

Case History

A 2 month old male child was admitted to the hospital with a history of fever, rashes and weakness. Rashes were present over the limbs and trunk. On examination, multiple, matted, superficial and deep cervical lymph nodes were present ranging in size from 1.5 to 3 cm. Hepatosplenomegaly was also present. Chest radiograph was normal. Ultrasound abdomen revealed hepatosplenomegaly with no focal lesions. Blood examination showed a hemoglobin of 6.4g/dL, total leukocyte count of 2500/mm3 with a normal differential count. Platelets were 40,000/mm3. The peripheral smear showed a macrocytic picture. Coagulation profile was normal except for thrombocytopenia.

Blood levels of lactate dehydrogenase were raised (1100 U/L). Serum ferritin was 690μg/L. Cytomegalovirus (CMV) IgM antibody detected by ELISA was positive in the child denoting recent infection which was later confirmed by polymerase chain reaction (PCR) method by detecting viral genome. The mother of the child was also positive for CMV IgM and IgG antibodies. Bone marrow aspiration showed hypocellularity with decreased granulopoiesis and erythropoiesis due to bone marrow suppression by CMV [Figure 1].

Figure 1

Photomicrograph of hypocellular bone marrow smear showing few macrophages and occasional normoblasts (H and E, ×400)

Fine needle aspiration cytology (FNAC) from cervical lymph nodes was performed with 23G needle and 10mL syringe in a syringe holder. Two to three passes were made, sufficient material was withdrawn and taken on slides and smeared. Smears were air dried and stained with May-Grünwald-Giemsa (MGG) stain. Stained smears revealed marked proliferation of histiocytes showing engulfment of erythrocytes, leucocytes, nuclear debris and platelets [Figure 2]. The histiocytes had abundant cytoplasm and eccentrically or centrally placed nuclei. Along with histiocytes, other inflammatory cells,viz., lymphocytes, neutrophils, giant cells and large number of eosinophils were also present against a background of lymphoglandular bodies, lymphoid tangles and red blood cells. A differential diagnosis of Langerhan's cell histiocytosis or histiocytosis X was considered; but lobulation and grooves in nuclei were not present, which are features of Langerhan's cells. To make a distinction between hemophagocytic syndrome and malignant histiocytosis may be difficult because of similarities in clinical presentation; however, the cells in hemophagocytic syndrome have a low nucleocytoplasmic ratio and abundant lightly staining cytoplasm containing large vacuoles of varying sizes and phagocytosed cells or cellular products. Nucleoli are not prominent and mitotic figures are rare.

Figure 2

Photomicrograph of FNAC of lymph node, revealing mixed inflammatory infiltrate and histiocytes (H and E ×100); Inset shows a macrophage with phagocytosis of a lymphocyte (H and E, ×1000)

Similar findings were revealed on histopathological examination of the lymph node biopsy. The lymph node was infiltrated by inflammatory cells and macrophages stuffed with red blood cells and nuclear debris [Figure 3]. Microscopy and culture for mycobacteria and fungi were negative on lymph node biopsy. Other serological tests for Epstein-Barr virus (EBV), human herpes virus and parvovirus were found to be negative.

Figure 3

Photomicrograph of lymph node biopsy showing infiltration by heavy inflammatory infiltrate (H and E, ×400)

Discussion

Hemophagocytic syndrome has been described in context of an autosomal recessive familial hemophagocytic syndrome (FHS), in association with viral and other infections and in various malignant diseases, mainly of lymphoid origin.[56] The organisms include parvovirus B19, herpes simplex virus (HSV), varicella zoster virus, Epstein-Barr virus, cytomegalovirus, influenza virus, coxsackie-virus, fungi, parasites, rickettsia, mycobacterium tuberculosis and other bacteria, including streptococcus pneumoniae.[7]

Virus associated hemophagocytic syndrome (VAHS) shows a predilection for children and immunocompromised adults. The pathogenesis of VAHS is not well understood. Many believe that viral infection provokes an abnormal immune response in predisposed individuals, leading to hyperactivation of TH1 helper cells, macrophage proliferation and hypercytokinemia.

Histiocyte Society proposed clinical, laboratory and histopathologic criteria for this rare entity. According to the Histiocyte Society protocol entitled ‘HLH”, five of the following criteria should be fulfilled in order to establish the diagnosis of HLH.[8]

Infection can be screened by various tests including serology, PCR, in situ hybridization and immunofluorescent antigen testing.

Fever for a period of ≥7 days

Splenomegaly

Cytopenia (≥2 lineages), anemia (Hb <9.0g/dL

Hypertriglyceridaemia (≥265mg/dL) and/or hypofibrinogenaemia (<1.5g/L)

Hemophagocytosis (Bone marrow < spleen, lymph nodes)

Low /absent natural killer cell activity

Hyperferritinemia (≥500μg/L)

Increased soluble CD25 >2400units/mL.

In our case, five out of the eight criteria were fulfilled. Our patient presented with fever, rash, hepatosplenomegaly and cervical lymphadenopathy. Peripheral blood film showed pancytopenia. Aspiration of bone marrow and cervical lymph nodes revealed histiocytic hyperplasia with activated macrophages showing engulfment of erythrocytes, leucocytes, platelets and their precursors. Similar findings were observed on lymph node biopsy. The patient was found to have definite serological evidence of cytomegalovirus infection. Patient's mother also revealed serologic evidence of CMV infection.

In terms of percentage, 0.5% -2% of newborn infants are infected with CMV but clinical illness occurs in less than 5% of those infected. Age range is 3 to 61 years (median 28 years).[6] Excessive hemophagocytosis is said to be due to release of chemokines and cytokines,-viz., interferon-γ; interleukin -1, 2 and 6; and tumor necrosis factor (TNF)-α. All reactive hemophagocytic syndromes have a similar morphology. A careful search for primary pathology is essential for effective treatment.

The diagnosis of HPS is frequently delayed because no genetic or biologic marker has been identified.

The clinical course of VAHS can be dramatic and the prognosis is often poor. The prognosis is more favorable in secondary forms. Chemotherapy combined with immunosuppression, along with treatment of primary cause, proves to be useful in secondary HPS; whereas transplantation of bone marrow or hematopoietic stem cells is the treatment of first choice in familial HPS.[9]

Our patient was put on cytotoxic therapy and he responded well.

Thus, hemophagocytic syndrome should always be taken into account in the differential diagnosis of fever with an obscure etiology.