Vignette Heme-Oncology # 1

1.
An 18-month-old infant presents with a skin eruption that consists of discrete red, orange, and yellow-brown papules . On physical examination, you note scaling dermatitis of the scalp, postauricular, perineal, and axillary areas. A skin biopsy reveals CD1a-positive monocyte macrophages that contain Birbeck granules.

Answer: This is LCH = langerhans cell histiocytosis

The infant described in the vignette exhibits physical findings and skin biopsy characteristics consistent with Langerhans cell histiocytosis (LCH).

The name of LCH has been applied to the class I histiocytoses , previously known as histiocytosis X, and includes the clinical entities of eosinophilic granuloma, Hand-Schüller-Christian disease, and Letterer-Siwe disease.

The normal Langerhans cell is an antigen-presenting cell of the skin. The hallmark of LCH is the Birbeck granule , a tennis racket-shaped bilamellar granule, which when seen in the cytoplasm of lesional cells in LCH, is diagnostic of the disease. Alternatively, LCH can be diagnosed definitively by demonstrating CD1a (surface markers on T cells) positivity of lesional cells.

Class II histiocytoses are characterized by accumulation of antigen-processing cells (ie, macrophages). These phagocytic cells lack the two class I markers (Birbeck granules and CD1a positivity) characteristic of LCH cells. The two major diseases of class II histiocytoses are familial erythrophagocytic lymphohistiocytosis and infection-associated hemophagocytic syndrome. In both diseases, disseminated lesions involve many organ systems. The lesions are characterized by infiltration of the involved organ with activated phagocytic macrophages and lymphocytes.

Class III histiocytoses are characterized by neoplastic proliferation of cells that have characteristics of monocytes/macrophages or their precursors. Acute monocytic leukemia and malignant histiocytosis are included in this category. In both conditions, Birbeck granules are absent, and cells are CD1a negative.

Thus to summarize: LCH includes:
# Eosinophilic granuloma, Hand-Schuller-Christian disease and letterer-Siwe disease.
# Birbeck granule is the hallmark of of LCH.
# CD1a is a surface marker for LCH.

2. DIC:

As the name indicates it is a (Intra Vascular) Coagulation, thus fibrin is deposited in the blood vessels. It also means that fibrinogen is being converted to fibrin, hence we will see:

*Low serum fibrinogen levels.

*Presence of increased Fibrionogen-degradation products (FDPs), like D- dimer. Thus serum D-dimer levels increase.

To summarize:

a] Lab diagnosis of DIC:

peripheral blood smear: may reveal fragmented, burr, or helmet-shaped red blood cells

Thrombocytopenia

prolonged prothrombin and partial thromboplastin times.

Low serum fibrinogen concentrations as well as the presence of fibrinogen degradation products (eg, D-dimers).

NB: Actually, serial measurement of fibrinogen is a very sensitive and specific test for DIC

b] Rx of DIC:

i) Find and treat the cause and correct the shock, acidosis, and hypoxia that complicate DIC. If these problems can be controlled, the bleeding quickly stops.

ii) Blood components, such as platelets, cryoprecipitate, or fresh frozen plasma, also may be required to help stop the hemorrhage.

NB: Continuous intravenous infusion of heparin and administration of specific factor concentrates (eg, activated protein C) are not used routinely in children.

3. In tumor Lysis syndrome: It was tested on the Board about serum sodium.

Serum Potassium: Elevated; Serum Phosphorous: Elevated;
Serum Lactate Dehydrogenase: Elevated; but Serum Sodium: Normal

NB: Because only intracellular ions are affected in TLS, serum sodium should be normal.

4. Similarly an important point about a patient with rhabadomyolysis (as happens in a young athlete after marathon):
Serum calcium may decrease. Why? Because calcium influx will happen in severely inflammed and traumatized muscles. This point has been tested on the Board.
Wheras, serum K, Phosphorous may increase.