The phenotype of individuals with glycogen storage disease (GSD) IX appears to be highly variable, even within subtypes. Features include short stature, fasting hypoglycemia with ketosis, hepatomegaly, and transaminitis. GSD IXɑ2 is caused by hemizygous pathogenic variants in PHKA2, and results in deficiency of the phosphorylase kinase enzyme, particularly in the liver. Like other GSDs, GSD IXɑ2 can present with hypoglycemia and post-prandial lactic acidosis, but has never been reported in a newborn, nor with lactic acidosis as the presenting feature. Here we describe the clinical presentation and course of a newborn boy with profound neonatal lactic and metabolic acidosis, renal tubulopathy, and sensorineural hearing loss (SNHL) diagnosed with GSD IXɑ2 through exome sequencing. Review of the literature suggests this case represents an atypical and severe presentation of GSD IXɑ2 and proposes expansion of the phenotype to include neonatal lactic acidosis and renal tubulopathy.

患有糖原贮积病（GSD）IX的个体的表型似乎是高度可变的，即使在亚型中也是如此。特征包括身材矮小，空腹低血糖症伴酮症，肝肿大和转氨酶。GSDIXɑ2是由PHKA2中的半合子致病变异引起的，并导致磷酸化酶激酶的缺乏，特别是在肝脏中。像其他GSD一样，GSDIXɑ2可能伴有低血糖症和餐后乳酸性酸中毒，但从未在新生儿中报道过，也没有乳酸性酸中毒作为表现特征。在这里，我们描述了通过外显子组测序诊断为GSDIXɑ2的患有严重新生儿乳酸和代谢性酸中毒，肾小管病变和感觉神经性听力减退（SNHL）的新生男孩的临床表现和病程。文献综述表明，该病例代表了非典型和严重的GSD IX and2表现，并建议将表型扩展至包括新生儿乳酸性酸中毒和肾小管病变。