Laboratory Studies
See the list below:
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Because natural killer (NK) cell function or activity is decreased in as many as 90% of patients with hemophagocytic lymphohistiocytosis (HLH), it is one of the most useful laboratory tests. NK cell number is usually not diagnostic.
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In addition to pancytopenia, hypofibrinogenemia, and hypertriglyceridemias, as previously mentioned, other laboratory abnormalities have been linked to hemophagocytic lymphohistiocytosis. Ferritin has been observed as a marker for hemophagocytic lymphohistiocytosis, with the serum levels paralleling the course of the disease. [33] A retrospective study evaluated the value of ferritin >500 ng/mL in diagnosing hemophagocytic lymphohistiocytosis in 344 consecutive patients admitted to the medical intensive care unit. The data suggested that a higher cutoff value of ferritin level may have improved utility in the diagnosis of secondary hemophagocytic lymphohistiocytosis in the critical care setting. [34]
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Liver damage has also been reported as evidenced by hyperbilirubinemia (see Bilirubin), hypoalbuminemia (see Albumin), and elevated findings on liver function tests including aspartate aminotransferase (AST) and alanine aminotransferase (ALT). [35]
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The presence of a PRF1 gene mutation can be determined based on flow cytometry by staining perforin contained in lymphocytes.
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The finding of a distinctive Th1/Th2 cytokine pattern (significant increase of interferon [IFN]-ƒ× and interleukin-10 [IL-10] with slightly increased or normal level of IL-6) may represent a useful biomarker for the early diagnosis, differential diagnosis, and the monitoring of the disease. [6]
Imaging Studies
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No specific imaging patterns are diagnostic of hemophagocytic lymphohistiocytosis.
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CT or ultrasonography findings may include ascites, gallbladder wall thickening, increased periportal echogenicity, lymphadenopathy, and pleural effusion.
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MRI may show CNS involvement, but the diagnosis is clinical and molecular, as is discussed below. [36]
Other Tests
In October 2002, Arico et al proposed an approach to the diagnostic workup of a patient with suspected hemophagocytic lymphohistiocytosis. [5]
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A detailed clinical history should be obtained to exclude other associated conditions, such as metabolic disorders or the DiGeorge syndrome. However, if the diagnostic hemophagocytic lymphohistiocytosis criteria are fulfilled, and the findings for associated conditions are negative, initial testing involves perforin expression by NK cells using flow cytometry.
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Patients lacking perforin expression should be analyzed for the PRF1 gene mutation.
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NK cell activity should also be determined to aid in differentiating between the hemophagocytic lymphohistiocytosis subtypes.
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Normal activity is suggestive of the reactive form of hemophagocytic lymphohistiocytosis rather than the familial type.
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DNA samples and fresh cells are suggested to be stored in case of need for future use in familial cases for which no genetic defect can be identified.
Procedures
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A skin biopsy can be performed for histological examination.
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Lymph node biopsy, bone marrow biopsy, or liver biopsy may demonstrate the characteristic hemophagocytosis.
A lymph node biopsy is performed. Note that a marking pen has been used to outline the node before removal and that a silk suture has been used to provide traction to assist the removal.
Histologic Findings
See the list below:
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A skin biopsy can assist in distinguishing this disorder from other systemic and potentially neoplastic diseases, such as Langerhans cell histiocytosis, myofibrosis, extramedullary hematopoiesis, and leukemia cutis. [1, 37] However, skin biopsy findings are usually not diagnostic and only rarely show hemophagocytosis.
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Because hemophagocytosis must be demonstrated in the bone marrow, spleen, or lymph nodes, appropriate specimens should be collected for documentation. [25] RBCs are affected more often than the white cells or platelets.
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Findings in up to two thirds of initial bone marrow aspirates may be nondiagnostic; thus, a negative examination finding may not rule out hemophagocytic lymphohistiocytosis.
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An additional bone marrow finding includes dyserythropoiesis, which has been observed in the absence of hemophagocytic histiocytes.
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Additional studies, including lymph node biopsy, should be performed, and treatment should not be delayed if all other criteria have been met. [38]
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Although problematic in a patient with a coagulopathy, a liver biopsy demonstrating a picture similar to chronic persistent hepatitis can support the diagnosis, as can the presence of mononuclear cells in the cerebrospinal fluid (CSF).
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A lymph node biopsy is performed. Note that a marking pen has been used to outline the node before removal and that a silk suture has been used to provide traction to assist the removal.
