Pearson syndrome with atypical presentation of short stature and atypical limb proportions - First reported case in Slovakia.

In this case report, we describe an individual with Pearson syndrome, representing the first reported case in Slovakia. The patient was 1.5-year-old boy with pancytopenia including macrocytic anemia, neutropenia and thrombocytopenia, pancreatic insufficiency, hepatopathy, psychomotor development delay, short stature and failure to thrive. The patient also had atypical symptoms for Pearson syndrome, including atypical limb proportions and facial dysmorphism, which contributed to the delay in correct diagnosis. In the whole exome sequencing (WES) analysis, virtual panels targeting genes associated with inborn errors of immunity and anemia were selected based on the patient's clinical phenotype, however no pathogenic variant was identified within these panels. During the evaluation of secondary findings, a pathogenic deletion, m.10952_15371del, was detected in mitochondrial DNA in a heteroplasmic state (55.8% in peripheral blood), leading to the diagnosis. Subsequently, MLPA analysis confirmed this deletion in other patient tissues (urine, bone marrow aspirate, buccal swab) with the highest level of heteroplasmy (70%) detected in the urine sample. Our study emphasizes the importance of a comprehensive diagnostic approach, including the analysis of several tissues, especially in the diagnosis of clinically complex mitochondrial diseases.