Renal defects and limb deficiencies in 197 infants: is it possible to define the "acrorenal syndrome"?

Ligase IV syndrome can present with microcephaly and radial ray anomalies similar to Fanconi anaemia plus fatal kidney malformations

Ligase IV (LIG4) syndrome is a rare disorder of DNA damage repair caused by biallelic, pathogenic variants in LIG4. This is a phenotypically heterogeneous condition with clinical presentation varying from lymphoreticular malignancies in developmentally normal individuals to significant microcephaly, primordial dwarfism, radiation hypersensitivity, severe combined immunodeficiency and early mortality. Renal defects have only rarely been described as part of the ligase IV disease spectrum.

We identified a consanguineous family where three siblings presenting with antenatal growth retardation, microcephaly, severe renal anomalies and skeletal abnormalities, including radial ray defects. Autozygosity mapping and exome sequencing identified a novel homozygous frameshift variant in LIG4, c.597_600delTCAG, p.(Gln200LysfsTer33), which segregated in the family. LIG4 is encoded by a single exon and so this frameshift variant is predicted to result in a protein truncated by 678 amino acids. This is the shortest predicted LIG4 protein product reported and correlates with the most severe clinical phenotype described to date. We note the clinical overlap with Fanconi anemia and suggest that LIG4 syndrome is considered in the differential diagnosis of this severe developmental disorder.

Blastogenetic associations: General considerations

Associations of anomalies, with VACTERL as the prototype, have been the source of much debate, including questions about the validity and definition of this category. Evidence is presented for a teratologic basis for associations involving interactions between disruptive events and specific vulnerabilities. Because the embryo is organized in time and space, differences in the timing, location, and severity of exposures will create variable sequelae for any specific vulnerability, creating associations. The blastogenetic stage of development involves distinct properties that affect the nature of associations arising during this time, including relatively undifferentiated developmental fields and causally nonspecific malformations. With this, single anomalies can be part of the spectrum of findings that comprise a specific association. A specific defect defines a subset of disturbances, biasing frequencies of other defects. Processes are basic, integrated, and general, so disruptions are often lethal, and can have multiple effects, accounting for high incidences of multiple anomalies, and overlaps between associations. Blastogenetic disturbances also do not affect the late "fine tuning" of minor anomalies, although pathogenetic sequences can occur. This model suggests that certain combinations of congenital anomalies can arise from causally nonspecific teratogenetic fields determined by timing, location, and vulnerabilities, rather than polytopic developmental fields.

Congenital anomalies of kidney and hand: a review

‘Acro-renal syndrome’ refers to co-occurrence of congenital renal and limb anomalies. The term acro-renal syndrome was coined by Curran et al. in 1972 though Dieker and Opitz were the first to report this phenomenon in three male patients in 1969. The common limb defects include oligodactyly, ectrodactyly, syndactyly or brachydactyly anomalies of the carpal and tarsal bones and the common renal anomalies observed are unilateral renal agenesis (URA), bilateral renal hypoplasia, ureteric hypoplasia, hydroureteronephrosis and duplication abnormalities. The acro-renal syndrome as originally described is rare, reported only in ∼20 patients in the international literature. We report a 23-year-old male patient with renal anomalies in the form of absent right kidney, left-sided vesicoureteric reflux (VUR) and skeletal anomalies viz short radius, absent first metacarpal ray in left hand and left undescended testis, consistent with Dieker's type acro-renal syndrome. Apart from the classical acro-renal syndrome, several anomalies of acro-renal patterns and the abnormal gene loci involved are described in the literature. This article is a comprehensive review of the development of kidneys, types of acro-renal syndromes, congenital anomalies of the kidney and urinary tract (CAKUT), syndromes associated with combined limb and renal anomalies, and anomalies associated with URA.

Further delineation of acro-renal-mandibular syndrome

A fetus with ectrodactyly, Pierre Robin sequence, renal aplasia and other anomalies is reported. The features are compared with other cases with limb and renal abnormalities reported in the literature. This case along with similar two cases reported by Halal and Tobias delineates acro-renal-mandibular syndrome as a distinct entity.