Two Siblings with LRPPRC Mutation: Mitochondrial Complex IV Deficiency: Case Report

Introduction: Mitochondrial diseases caused by mutations in the LRPPRC gene are rare and lead to multisystemic dysfunction. We report two siblings from consanguineous Iraqi parents, both harboring a rare homozygous deletion in LRPPRC (c.2726_2728del; p.Lys909del), previously reported in one other patient. These cases contribute to the expanding phenotypic and geographic spectrum of LRPPRC-related mitochondrial disease. Case Presentation: The younger sibling, a 9-year-old girl, presented with severe growth retardation, global developmental delay, hypotonia, spastic ataxic gait, and lactic acidosis. Magnetic resonance imaging showed symmetrical hyperintensities in the mesencephalon and thalami, cerebellar atrophy, and an inverted lactate peak on spectroscopy. Hypertrophic cardiomyopathy was also detected. The older sibling, aged 13, exhibited milder manifestations, including axial hypotonia, tremor, ataxia, and persistent hyperlactatemia. Both siblings had elevated lactate levels but otherwise normal metabolic panels. Whole exome sequencing revealed a homozygous mutation in the LRPPRC gene (c.2726_2728del; p.Lys909del) in both patients. Conclusions: These cases highlight the clinical variability of LRPPRC-related disorders. Our report underscores the importance of considering LRPPRC mutations in the differential diagnosis of early-onset neurodevelopmental delay and multisystemic dysfunction with lactic acidosis, especially in populations with high rates of consanguinity. Early genetic diagnosis via whole exome sequencing is essential for accurate diagnosis, genetic counseling, and family planning.