Unraveling a history of overlap: A phenotypic comparison of RBCK1-related disease and glycogen storage disease type IV.

RBCK1-related disease is a rare, multisystemic disorder for which our current understanding of the natural history is limited. A number of individuals initially carried clinical diagnoses of glycogen storage disease IV (GSD IV), but were later found to harbor RBCK1 pathogenic variants, demonstrating challenges of correctly diagnosing RBCK1-related disease. This study carried out a phenotypic comparison between RBCK1-related disease and GSD IV to identify features that clinically differentiate these diagnoses. Literature review and retrospective chart review identified 25 individuals with RBCK1-related disease and 36 with the neuromuscular subtype of GSD IV. Clinical features were evaluated to assess for statistically significant differences between the conditions. At a system level, any cardiac, autoinflammation, immunodeficiency, growth, or dermatologic involvement were suggestive of RBCK1, whereas any respiratory involvement suggested GSD IV. Several features warrant further exploration as predictors of RBCK1, such as generalized weakness, heart transplant, and recurrent infections, among others. Distinguishing RBCK1-related disease will facilitate correct diagnoses and pave the way for accurately identifying affected individuals, as well as for developing management recommendations, treatment, and an enhanced understanding of the natural history. This knowledge may also inform which individuals thought to have GSD IV should undergo reevaluation for RBCK1.

Expansion of the prenatal phenotype of Baraitser-Winter syndrome: Presentation of two cases of multiple congenital anomaly syndrome.

Baraitser-Winter cerebrofrontofacial syndrome (BWCFF) is a variable multiple congenital anomaly condition, typically presenting postnatally with neurocognitive delays, distinctive facial features, cortical brain malformations, and in some, a variety of additional congenital malformations. However, only a few cases have reported the prenatal presentation of this syndrome. Here, we report two cases of BWCFF and their associated prenatal findings. One case presented with non-immune hydrops fetalis and a horseshoe kidney and was found to have a de novo heterozygous variant in ACTB (c.158A>G). The second case presented with gastroschisis, bilateral cleft lip and palate, and oligohydramnios, and was found to harbor a different de novo variant in ACTB (c.826G>A). Limited reports exist describing prenatally identified anomalies that include fetal growth restriction, increased nuchal fold, bilateral hydronephrosis, rocker bottom foot, talipes, cystic hygroma, omphalocele, and hydrops fetalis. In addition, only three of these cases have included detailed prenatal imaging findings. The two prenatal cases presented here demonstrate an expansion of the prenatal phenotype of BWCFF to include gastroschisis, lymphatic involvement, and oligohydramnios, which should each warrant consideration of this diagnosis in the setting of additional anomalies.

The Reliability of Ultrasound Markers in Identifying Fetuses With a Life-Limiting Skeletal Dysplasia.

OBJECTIVE: To determine the diagnostic performance of ultrasound markers associated with life-limiting fetal skeletal dysplasia in a fortified cohort. METHODS: Retrospective review from 2013 to 2023 of pregnancies with suspected fetal skeletal dysplasia. Ultrasound evaluation included measurements predictive of a life-limiting dysplasia: thoracic circumference/abdominal circumference (TC/AC) < 0.6, femur length/abdominal circumference (FL/AC) < 0.16, and thoracic circumference (TC) < 2.5th percentile. Demographics, ultrasound findings, genetic testing, and fetal/neonatal outcome were reviewed. RESULTS: Of 96 fetuses with complete outcome data, 47 (49%) had a non-life-limiting dysplasia and 49 (51%) had a life-limiting dysplasia. 22 (23%) had no life-limiting markers, 42 (44%) had one, 27 (28%) had two, and 5 (5%) had three. FL/AC < 0.16 and TC < 2.5th percentile were associated with life-limiting dysplasia (p < 0.001; p < 0.001), while TC/AC < 0.6 was rare and did not reach statistical significance (p = 0.056). The positive predictive value (PPV) for predicting life-limiting dysplasia increased from 50% to 78% to 100% with one, two, or three markers. The PPV of the two life-limiting markers was significantly higher in those diagnosed at < versus ≥ 28 weeks (90% vs. 43%, p = 0.02) but the analysis was limited by small numbers in the ≥ 28 weeks cohort. The negative predictive value of no life-limiting markers was 91%. CONCLUSIONS: In our cohort, the presence of two life-limiting ultrasound markers prior to 28 weeks was highly suggestive of a life-limiting dysplasia, whereas the absence of life-limiting markers was strongly associated with a non-life-limiting dysplasia throughout gestation. Nonetheless, individual markers had a poor predictive value of lethality, and a life-limiting diagnosis ≥ 28 weeks is challenging based on ultrasound markers alone. This highlights the importance of integrating thorough sonography, genetic testing, and balanced parental counseling.