Resumen Objetivos La distrofia miotónica tipo 1, conocida también como enfermedad de Steinert, es un desorden multisistémico crónico, degenerativo e incapacitante de expresividad clínica muy variable provocado por una expansión heredada de manera autosómica dominante de la repetición del triplete citosina-timina-guanina, localizada en la región 3′ no codificante del gen DMPK (19q13.3). Caso clínico En este estudio, presentamos el caso de una familia con varias expansiones de la repetición CTG intergeneracionales, con un caso adicional de falsa sospecha de fenómeno de contracción, debido a las limitaciones de la técnica TP-PCR. Conclusiones La inestabilidad meiótica de las repeticiones de (CTG)n provoca anticipación genética. De este modo, a lo largo de las sucesivas generaciones, se ha hallado un incremento del tamaño de la mutación DM1 y un fenotipo más severo en los individuos afectados. Aunque es extremadamente infrecuente, en la transmisión de padres a hijos, también puede producirse una disminución en el número de repeticiones de CTG, siendo esta más frecuente en la transmisión paterna.

Objectives Myotonic dystrophy type 1 (DM1), also known as Steinert’s disease, is a chronic, progressive and disabling multisystemic disorder with a broad spectrum of severity that arises from an autosomal-dominant expansion of the Cytosine-Thymine-Guanine (CTG) triplet repeat in the 3′ untranslated region of the DMPK gene (19q13.3). Case presentation In this study, we report the case of a family with several intergenerational expansions of the CTG repeat, with an additional case of a false suspicion of contraction phenomenon due to TP-PCR limitations. Conclusions The meiotic instability of the (CTG)n repeats leads to genetic anticipation where increased size of DM1 mutation and a more severe phenotype have been reported in affected individuals across generations. Even if extremely rare, a decrease in the CTG repeat size during transmission from parents to child can also occur, most frequently during paternal transmissions.

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Hemophagocytic lymphohistiocytosis (HLH) is a rare but fatal disorder characterized by the proliferation and infiltration of macrophages and hyperactivated T lymphocytes that escape from the physiological control pathways and favour the existence of an environment of excessive inflammation and tissue destruction. HLH has been classified into two types: a primary or familial autosomal recessive form, caused by mutations in genes encoding proteins involved in the granule-dependent cytotoxic pathway (familial hemophagocytic lymphohistiocytosis [FHL] types 1–5); and other secondary or acquired form, generally associated with infections, malignancy, autoimmune diseases, metabolic disorders or primary immunodeficiencies. Since the first familial hemophagocytic lymphohistiocytosis-2 (FHL2) causative mutation in the PRF1 gene was described in 1999, more than 200 mutations have been identified to date. Here, we report the first case of very late-onset FHL2 in a Spanish 72-year-old female with splenomegaly, hypertriglyceridemia, hypofibrinogenemia, pancytopenia and marrow hemophagocytosis harbouring in heterozygosity two PRF1 variants proposed as causative in this study. The heterozygous mutation c.445G>A (p.Gly149Ser) identified in the exon 2 results in a missense mutation previously described as a probable pathogenic variant associated with the development of FHL2. Affecting the same exon, c.272C>T (p.Ala91Val) is the most prevalent variant of this gene. Although it was initially classified as benign, recent studies support its potential pathogenic role, considering it a variant of uncertain significance associated with a risk of developing FHL2. The genetic confirmation of FHL made possible an adequate counselling to the patient and direct relatives and provided important information for her control and follow-up.