Gamopatias monoclonais: critérios diagnósticos e diagnósticos diferenciais Monoclonal gammopathies: diagnosis criteria and differential diagnosis

As gamopatias monoclonais constituem um grupo de desordens caracterizado pela proliferação monoclonal de plasmócitos, que produzem e secretam imunoglobulina ou fragmento de imunoglobulina monoclonal (proteína M) . Este artigo propõe uma revisão dos critérios diagnósticos das principais gamopatias monoclonais e diagnósticos diferenciais, uma vez que é comum a sobreposição de muitas características clínicas entre suas variantes. A gamopatia monoclonal de significado indeterminado (MGUS) é definida pela presença de proteína M sérica 30% ou plasmocitoma documentado por biópsia. Se a lesão óssea decorre de plasmocitoma solitário ou somente osteoporose, sem fratura, a plasmocitose medular também precisa ser > 30%, para preencher critérios de MM. As gamopatias monoclonais podem estar associadas a diversas doenças, incluindo desordens linfoproliferativas, reumatológicas, neurológicas, dermatológicas e infecciosas. A definição das características clínicas e laboratoriais de cada entidade, maligna ou benigna, facilita o diagnóstico das gamopatias monoclonais e, como conseqüência, seu manejo clínico pelos médicos assistentes.Monoclonal gammopathies are a group of disorders characterized by proliferation of monoclonal plasma cells, which produce and secrete monoclonal immunoglobulin or fragments of monoclonal immunoglobulin (M protein). This paper proposes to review diagnostic criteria of the most important monoclonal gammopathies and their differential diagnosis, because superposition of many clinical characteristics is common between variants. The monoclonal gammopathy of undetermined significance (MGUS) is defined by the presence of serum M protein < 3g/dL and/or urinary M protein < 1g/24h, bone marrow plasma cell < 10%, and absence of organ and tissue damage. Asymptomatic multiple myeloma (MM) is characterized by the presence of M protein, bone marrow or tissue biopsy plasma cell infiltration, and non-compliance of the criteria for MGUS, symptomatic MM and solitary plasmacytoma. Symptomatic MM is a plasma cell neoplasm associated with serum or urinary M protein, bone marrow or tissue biopsy plasma cell infiltration and related organ or tissue damage: elevated calcium levels, renal insufficiency, anemia and bone lesions. If no M protein is detected (nonsecretory MM), then at least 30% monoclonal bone marrow plasma cell infiltration and/or a biopsy-proven plasmacytoma is required for MM diagnosis. If a solitary (biopsy-proven) plasmacytoma or osteoporosis (without fractures) are the sole defining criteria, then at least 30% plasma cells are required in the bone marrow for MM diagnosis. Monoclonal gammopathies may be associated with many different diseases, including lymphoproliferative disorders, connective tissue disorders, neurologic, dermatologic and infectious diseases. The clinical and laboratorial characteristics should be very well defined in each variant, malign or benign, easily determining the diagnosis of monoclonal gammopathies and then their clinical management