Table 3.

Genetic Disorders Associated with Radial Aplasia in the Differential Diagnosis of Thrombocytopenia Absent Radius Syndrome

Gene(s)DisorderMOILimb MalformationsOther Key Features
23 genes 1 Fanconi anemia AR
AD
XL 2		Unilateral or bilateral malformations of upper limbs (e.g., hypoplastic thumb & hypoplastic radius) & lower limbsGrowth deficiency, variable congenital anomalies, BMF, & ↑ risk for malignancy
ESCO2 ESCO2 spectrum disorder (from Roberts syndrome at severe end of spectrum to SC phocomelia at milder end)ARLimb malformations can incl bilateral symmetric tetraphocomelia or hypomelia caused by mesomelic shortening & limb bone fusions; brachydactyly & oligodactyly w/abnormal thumb placement, hypoplasia, or aplasiaPrenatal growth restriction, craniofacial abnormalities, other congenital anomalies, & ID
RECQL4 RAPADILINO syndrome (See Rothmund-Thomson Syndrome, Genetically Related Disorders.)ARRadial defects incl absent or hypoplastic radii & absent or hypoplastic thumbs; absent/hypoplastic patellaeGrowth deficiency, high cleft palate, diarrhea, joint dislocations, & characteristic facial features
SALL1 Townes-Brocks syndrome ADThumb malformations w/normal radiiImperforate anus, dysplastic ears, hearing impairment, & kidney disease
SALL4 SALL4-related disorders (Duane-radial ray syndrome [Okihiro syndrome], acro-renal-ocular syndrome, & SALL4-related Holt-Oram syndrome)ADRadial ray anomalies of varying severity, ranging from thenar hypoplasia to radial aplasiaDuane anomaly & renal abnormality
TBX5 TBX5-related Holt-Oram syndromeADUpper limb malformations range from triphalangeal or absent thumb(s) to phocomelia; radius aplasia/hypoplasia, fusion or anomalous carpal & thenar bones, & restriction of shoulder joint movementCongenital heart malformation & cardiac conduction disease

AD = autosomal dominant; AR = autosomal recessive; BMF = bone marrow failure; ID = intellectual disability; MOI = mode of inheritance; XL = X-linked

1.

BRCA1, BRCA2, BRIP1, ERCC4, FAAP100, FANCA, FANCB, FANCC, FANCD2, FANCE, FANCF, FANCG, FANCI, FANCL, FANCM, MAD2L2, PALB2, RAD51, RAD51C, RFWD3, SLX4, UBE2T, XRCC2 (See Fanconi Anemia.)

2.

Fanconi anemia (FA) can be inherited in an autosomal recessive manner, an autosomal dominant manner (RAD51-related FA), or an X-linked manner (FANCB-related FA).

From: Thrombocytopenia Absent Radius Syndrome

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