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Um desafio diagnóstico de nefropatia a LMX1B : revisão teórica a propósito de um caso clínico
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A síndrome Unha-patela (SUP) é uma doença multisistémica rara com hereditariedade autossómica dominante. Esta síndrome caracteriza-se por displasia das unhas e alterações típicas do esqueleto ósseo. As manifestações renais, embora raras, são um fator determinante da mortalidade e podem constituir a sua única manifestação.
Apresenta-se o caso de uma doente do sexo feminino, previamente saudável, com diagnóstico de síndrome nefrótica aos 23 anos. Na investigação etiológica foram excluídas doenças auto-imunes e virais e realizada biópsia renal que foi compatível com doença de lesões mínimas. Por apresentar resistência aos corticóides foi repetida biópsia renal que confirmou o primeiro diagnóstico histológico. A IS foi alterada para um inibidor da calcineurina e, após um ano, por ausência de remissão completa optou-se por terceira linha de IS com micofenolato de mofetil associado a corticoterapia. A doente manteve proteinúria subnefrótica e a terceira biópsia renal, doze anos após o diagnóstico inaugural, confirmou a doença de lesões mínimas. Dezasseis anos após o diagnóstico, na tentativa de suspensão de corticoterapia, foi administrado rituximab sem benefício na redução da proteinúria. Apesar da ausência de história familiar, realizou-se o estudo genético de síndromes nefróticas que revelou mutação no gene LMX1B em heterozigotia. O diagnóstico de SUP permitiu a suspensão de imunossupressão, mantendo-se a proteinúria controlada com medidas anti-proteinúricas.
Este caso ilustra a dificuldade de diagnosticar síndromes hereditárias raras na ausência de história familiar e de manifestações extra-renais e a importância de serem consideradas as causas genéticas perante uma síndrome nefrótica resistente à imunossupressão.
Nail-patella syndome (NPS) is a rare multisystemic disorder of autosomal dominant inheritance. This syndrome is characterized by nail dysplasia and skeletal alterations. Renal involvement, although rare, is a major determinant of mortality and may be the only manifestation of the disease. We present the case of a female patient diagnosed with nephrotic syndrome at 23 years old. In the etiological investigation, autoimmune and viral diseases were excluded, and a renal biopsy was performed. The latter was compatible with minimal change disease. The patient was corticoresistant so the renal biopsy was repeated and confirmed the first histological diagnosis. Because of this result, the immunosuppressive therapy was changed to a calcineurin inhibitor. One year later, because there was absence of complete remission, treatment was escalated to the third line of immunosupression (mycophenolate mofetil plus corticosteroids). The patient´s proteinuria fluctuated at subnephrotic levels. The third renal biopsy, twelve years from the beginning of the investigation, confirmed the diagnosis of minimal change disease. Trying to stop steroid treatment, after sixteen years of follow up, rituximab was administered without remission of proteinuria. Despite the absence of a family history, a genetic study of idiopathic nephrotic syndrome was conducted. This study revealed a heterozygous mutation in LMX1B gene. The patient was diagnosed with NPS so the immunosupression was suspended and antiproteinuric therapy was optimized. This case shows the difficulty of diagnose rare hereditary syndromes in the absense of family history and extra-renal manifestations and the importance of considering genetic causes in the presence of a nephrotic syndrome resistant to immunossupression.
Nail-patella syndome (NPS) is a rare multisystemic disorder of autosomal dominant inheritance. This syndrome is characterized by nail dysplasia and skeletal alterations. Renal involvement, although rare, is a major determinant of mortality and may be the only manifestation of the disease. We present the case of a female patient diagnosed with nephrotic syndrome at 23 years old. In the etiological investigation, autoimmune and viral diseases were excluded, and a renal biopsy was performed. The latter was compatible with minimal change disease. The patient was corticoresistant so the renal biopsy was repeated and confirmed the first histological diagnosis. Because of this result, the immunosuppressive therapy was changed to a calcineurin inhibitor. One year later, because there was absence of complete remission, treatment was escalated to the third line of immunosupression (mycophenolate mofetil plus corticosteroids). The patient´s proteinuria fluctuated at subnephrotic levels. The third renal biopsy, twelve years from the beginning of the investigation, confirmed the diagnosis of minimal change disease. Trying to stop steroid treatment, after sixteen years of follow up, rituximab was administered without remission of proteinuria. Despite the absence of a family history, a genetic study of idiopathic nephrotic syndrome was conducted. This study revealed a heterozygous mutation in LMX1B gene. The patient was diagnosed with NPS so the immunosupression was suspended and antiproteinuric therapy was optimized. This case shows the difficulty of diagnose rare hereditary syndromes in the absense of family history and extra-renal manifestations and the importance of considering genetic causes in the presence of a nephrotic syndrome resistant to immunossupression.
Descrição
Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2021
Palavras-chave
Síndrome Unha-Patela Nefropatia associada a LMX1B Doença de lesões mínimas Síndrome nefrótica corticorresistente Nefrologia