| Rapadilino syndrome | |
|---|---|
| Other names | Radial and patellar aplasia, Radial and patellar hypoplasia |
 | |
| Rapadilino syndrome has an autosomal recessive pattern ofinheritance. | |
| Specialty | Musculoskeletal |
| Symptoms | Underdevelopment orabsences of the bones in the forearms, thumbs, and kneecaps,cleft palate or high-arched, palate, diarrhea, andshort stature. |
| Usual onset | Infancy[1] |
| Duration | Lifelong |
| Causes | Mutations in the RECQL4 gene[2] |
| Frequency | Less than 1,000 known cases in the United States[1] |
RAPADILINO syndrome is anautosomal recessive disorder characterized by:[3]
It is more prevalent inFinland than elsewhere in the world.[4] It has been associated with the geneRECQL4.[4] This is also associated withRothmund–Thomson syndrome[5] and Baller–Gerold syndrome.[6]
Most people with RAPADILINO syndrome haveunderdeveloped orabsent bones in theforearms andthumbs.Kneecaps may beunderdeveloped orabsent. Other characteristics include acleft orhigh-arched palate, a long, narrownose, anddislocated joints.[2]
Many infants with RAPADILINO suffer feeding difficulties, as well asdiarrhea andvomiting. A combination ofpoor bone development andnutritional deficiencies can causeslow growth andshort stature.[2]
Some RAPADILINO syndrome patients have harmless light brown patches of skin that resemblecafé-au-lait spots. Patients with RAPADILINO syndrome are more likely to developosteosarcoma orlymphoma. In those with RAPADILINO syndrome,osteosarcoma typically develops during childhood or adolescence, whereaslymphoma develops in early adulthood.[2]
RAPADILINO syndrome is caused byRECQL4 gene mutations. TheRECQL4 gene gives instructions to produce a member of a protein family known asRecQ helicases.Helicases areenzymes that temporarily bind toDNA and unwind theDNA molecule'stwo spiral strands. This unwinding is needed forDNA replication to prepare forcell division and formending damaged DNA. TheRECQL4 protein is involved inDNA replication andrepair as well as the stability ofgenetic information incells.[2]
The most frequentRECQL4gene mutation linked to RAPADILINO syndrome causes theRECQL4 protein to be misassembled. Thisgenetic mutation causes the formation of a protein that lacksexon 7, therefore cannot function as ahelicase. In the lack ofhelicase function, normalDNA replication andrepair may be impaired resulting in widespreadgenetic damage. Although it is unknown howRECQL4 genemutations produce RAPADILINO syndrome's specific symptoms, these changes may result in the accumulation ofDNA errors andcell death.[2]
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