A Small-for-Gestational-Age Infant with MIRAGE Syndrome Who Developed Heat Stroke and Rhabdomyolysis due to Severe Temperature Instability.

MIRAGE syndrome is characterized by myelodysplasia, infection, restriction of growth, adrenal hypoplasia, genital phenotypes, and enteropathy. This report describes heat stroke and rhabdomyolysis caused by anhidrosis as a symptom of MIRAGE syndrome in a small-for-gestational-age (SGA) female neonate born at 32 weeks of gestation (birth weight, 911 g [-3.8 SD]). She developed severe temperature instability with anhidrosis, growth failure, mild developmental delay, hypothyroidism, and intractable enteropathy. On day 156, her temperature reached 42.0°C; her fever persisted for 2 h with prolonged irritability. Her serum creatine kinase level increased to a peak value of 12,716 (normal range, 43-321) IU/L. The clinical feature was diagnosed as rhabdomyolysis caused by heat stroke, which resulted from physical exertion with anhidrosis. Her SAMD9 variant was c.2945G>A, p. (Arg982His). Neonatologists should be aware of MIRAGE syndrome as a differential diagnosis of SGA with temperature instability.