Type III aminoterminal propeptide of procollagen in some haematological malignancies.

Marrow fibrosis is involved in some haematological malignancies. Either because of sampling errors, variations of focal distribution of fibrosis or the discomfort for patients of bone biopsies, conventional histology appears to be unsuitable for the follow-up of myelofibrosis. During collagen synthesis by marrow fibroblasts, the aminoterminal propeptide is removed from procollagen III and released in the serum. Thus, a sensitive radioimmunoassay of type III aminoterminal propeptide of procollagen (PC III) has been tested in myeloproliferative and lymphoproliferative disorders with a marked bone marrow fibrosis. In polycythaemia vera, PC III level was significantly increased as compared to controls and was related to marrow fibrosis of grade I. The more increased PC III values were observed in spent polycythaemia cases initially treated by phlebotomy alone. Follow-up showed a transformation into myeloid metaplasia. In contrast, PC III remained stable in patients treated with radiophosphorus 32P or hydroxyurea who did not transform. In myeloid metaplasia, results of PC III were significantly higher than in controls or polycythaemia vera cases. Myelofibrosis of recent onset (less than 2 years) gave higher values than chronic myelofibrosis. Increased PC III values were also emphasized in chronic myelocytic leukaemia, and in a few cases of refractory anaemia with excess of blasts, hairy cell leukaemia and chronic lymphocytic leukaemia.