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During the last three years 77 patients with myelofibrosis were studied by scintigraphy, using 99m Tc colloids and 111 In transferrin as tracers. Low axial uptake of the colloids, extension of the indium uptake beyond the axis towards the knees and sometimes the ankles and elbows, and splenic indium uptake are valuable diagnostic criteria, particularly useful to exclude myelofibrosis associated with a malignant disorder. The clinical severity of the disease, and in particular the disappearance of a physiologically active bone marrow (indium uptake) can be predicted from isotopic studies. Bone marrow scintigraphy could contribute to the difficult decision of splenectomy.

Screening for red cell defects, and exploration of cellular and humoral immunity has been performed in 33 patients : 31 had agnogenic myelosclerosis with myeloid metaplasia, 3 had polycythemia vera with secondary myelosclerosis. No patient had the biological abnormalities characteristical of paroxysmal nocturnal hemoglobinuria (Marchiafava-Micheli). In 19 out of 21 cases, red cells had antigen i on their membrane, thus suggesting that splenic erythropoiesis could give rise to immature erythrocytes. Two patients had a monoclonal dysglobulinemia, 5 a positive Coombs test, 6 a rhumatoid factor in the serum, 3 antitissue antibodies, 1 LE cells, 3 a positive Paul-Bunnel-Davidsohn test without mononucleosis, 11 a negative skin test. Implications of the uncommon occurrence of these dissorders are discussed.

Nine patients were selected according to the following criteria: 1. Hematological findings consistent with the diagnosis of myelofibrosis with myeloid metaplasia (MMM), except for an excess of blasts in the blood and bone marrow; 2. No previous (silent) phase of MMM. 3. No PH1 chromosome, and 4. No identifiable cause of secondary myelofibrosis. These patients had either an acute or subacute myelofibrosis. The onset of such symptoms as fever, bone pain, hemorrhage and mild splenomegaly was rapid. Terminal acute leukemia or more often progressive bone marrow biopsy showing myelofibrosis with persistence of differentiated myeloid tissue, particularly megacaryocytes. Isotopic studies (59Fe and 51Cr) showed splenic erythroid metaplasia, poor bone marrow 59Fe uptake and increased peripheral red blood cell destruction. This study confirms that malignant myelosclerosis is a well-defined syndrome which must be distinguished from: a) Acute transformation of typical agnogenic myeloid metaplasia even though it was previously undiagnosed (4 cases of MMM illustrating this possibility have been reported); b) Acute myeloblastic leukemia with myelofibrosis; and c) Myelofibrosis secondary to lymphomatous or carcinomatous bone-marrow invasion (2 cases with acute myelofibrosis appearing long after appropriate treatment have been reported).