A 66-year-old man was admitted into our Hospital in November 2008 with splenomegaly, a high red cell count, and subnormal serum erythropoietin levels.
Cytogenetic analysis showed a normal male karyotype.
Molecular studies were negative for the BCR-ABL1 rearrangement, but revealed the JAK2V617F mutation with an allele burden of 44.9%.
A diagnosis of PV was made on the basis of a morphological bone marrow analysis according to the WHO 2008 criteria.
The patient was started on aspirin, hydroxyurea, and phlebotomies, all of which were well tolerated.
Six years later, an abdominal ultrasound scan revealed the presence of dense bilateral perinephric infiltration, which was confirmed by a whole-body computed tomography (CT) scan, and a fluotine-18 fluordeoxyglucose positron emission tomography (F-FDG-PET) scan demonstrated increased glucose uptake in the medullary channels of both humeri and femurs.
Morphological bone marrow analysis confirmed the previous diagnosis of PV and showed no evident change in the grading of bone marrow fibrosis (MF-0 according to the EUMNET consensus),13 whereas cytogenetic analysis revealed the following complex male karyotype: 47,XY,+9[2/20],47,XY,add(6)(p25),+9[2/20],46,XY[16/20].
The histological nature of the perinephric infiltration was identified by means of a CT-guided core biopsy of the lesion.
Morphological analysis demonstrated the accumulation of foamy histiocytes that were positive for CD68 and negative for the dendritic cell markers CD1a and S100, surrounded by fibrosis and a scanty lympho-monocytic infiltrate (Figure ​(Figure1).1).
The detection of the BRAFV600E mutation led to a diagnosis of ECD.
Cardiac magnetic resonance imaging (MRI) revealed pseudo-tumoral infiltration of the atrioventricular wall,14 and a bone scan showed symmetrically irregular radiotracer uptake in the long bones of the limbs consistent with ECD (Figure ​(Figure22)2; the findings of cerebral and pulmonary imaging were negative.
In accordance with the most recent guidelines for the treatment of ECD,1 the patient started therapy with pegylated interferon (IFN)-alpha and, after 3 months of treatment, a new abdominal ultrasound scan revealed the complete resolution of the dense bilateral perinephric infiltration, and the normalization of the blood cell counts was achieved.