Clinical Features and Short-Term Growth Hormone Outcomes in Maternal UPD of Chromosome 20: Five Chinese Patients and a Literature Review.

BACKGROUND: Maternally derived uniparental disomy of chromosome 20 [UPD(20)mat], also known as Mulchandani-Bhoj-Conlin syndrome (MBCS), is a rare imprinting disorder with fewer than 30 cases documented to date. It is characterized by prenatal and postnatal growth failure and feeding difficulties. Herein, we aimed to summarize the clinical and growth characteristics of UPD(20)mat and describe short-term growth outcomes during recombinant human growth hormone (rhGH) exposure in affected individuals. METHODS: We retrospectively analyzed five Chinese children with UPD(20)mat genetically evaluated by whole-exome sequencing (WES), methylation-specific multiplex ligation-dependent probe amplification, or short tandem repeat analysis. Clinical manifestations and growth data were collected. Four patients received rhGH therapy and were evaluated for changes in height standard deviation scores (Ht-SDS). In addition, we conducted a structured narrative review of 23 previously published cases identified in PubMed, CNKI, and WanFang through July 19, 2026. RESULTS: The cohort included three female and two male children, with a median age at diagnosis of 3.4 years. Predominant features included advanced maternal age (3/4), postnatal feeding difficulties with low body mass index (BMI), and low absolute serum insulin-like growth factor-1 concentrations in the available records. Facial dysmorphism was mild and predominantly characterized by a prominent forehead and relative macrocephaly. Neurodevelopmental delay was noted in 4/5 patients. After rhGH treatment (duration: 10-15 months), the four treated patients showed substantial short-term catch-up growth, achieving a mean annualized height velocity of 10.7 cm/year and a mean increase in Ht-SDS of +1.18 (range: +0.7 to +2.0). The narrative review identified postnatal growth failure (93%) and feeding difficulties (100%) as cardinal features. CONCLUSION: To our knowledge, this study reports the largest case series of Chinese patients with UPD(20)mat to date, highlighting that neurodevelopmental delay and hypotonia are frequent features of this condition. rhGH exposure was associated with short-term increases in linear growth, but the findings are exploratory and do not establish efficacy. Compared with SRS, facial dysmorphism was mild and non-specific, underscoring the importance of early genetic testing in children with unexplained early-onset growth failure.