Immunodeficiency and severe gastrointestinal manifestations in a patient with novel DKC1 mutations causing Hoyeraal–Hreidarsson syndrome

Abstract

Background: Hoyeraal–Hreidarsson syndrome (HHS) is considered a clinically severe variant of dyskeratosis congenita (DKC) and represents the extreme phenotype caused by aberrant telomere biology. Unlike patients with DKC who present later in life, most cases of HHS present in the first years of life. Clinical features include intrauterine growth restriction and microcephaly, which are universal but not pathognomonic, as well as gastrointestinal, immunological and neurological manifestations. The immunological profile is varied as a result of cellular immunodeficiency, humoral defects, or both, and may be the presenting symptom of these patients. Moreover, the immunological phenotype can change over time, making HHS a diagnostic challenge. Methods: This case report highlights the clinical presentation and immune investigations of a male patient with a novel mutation in DKC1, causing HHS. Results: Here, we describe a patient with HHS who presented with Pneumocystis jiroveci pneumonia and low T cells, which is typical of severe combined immunodeficiency. Over time, he developed agammaglobulinemia whereas T-cell function improved. He also presented with extremely severe gastrointestinal manifestations, and died at 3 years of age. Conclusion: This case report highlights a novel compound heterozygous mutation in DKC1, and the need to consider HHS as the differential diagnosis of patients with combined immunodeficiency. Statement of novelty: The case reports on a novel mutation in DKC1.