Ciliopathies

Ciliopathies refer to diseases due to malfunctioning cilia (singular: cilium). Cilia are organelles that are external extensions of the cell membrane. Cilia fall into two main types: primary (or immotile) cilia and motile cilia.

Clinical presentation

Primary cilia are found in virtually every cell type, resulting in a wide range of anomalies, including central nervous system, eye, heart, kidney, liver, and skeletal abnormalities.

Pathology

Ciliopathies are caused by malfunctioning cilia. Primary cilia have important roles in cell signaling, transduction of sensory stimuli, and cell cycle control.  Motile cilia are restricted to a few specialized tissues including cells of the respiratory tract, the ependyma of the ventricles and cisterns of the CNS, spermatozoa, and the Fallopian tubes. Motile cilia are also important during embryogenesis.

Classification

There are a number of ciliopathies that can be broadly classified as being either due to motile or primary cilia malfunction. See individual articles for in-depth discussions.

• motile cilia malfunction:
  • Kartagener syndrome (bronchi "primary" ciliary dyskinesia, note that in this peculiar case "primary" bears the meaning "congenital" in the literature)
• primary (immotile) cilia malfunction:
  • Joubert syndrome and Joubert syndrome-related disorders:
    • COACH syndrome
    • Dekaban-Arima syndrome
    • Leber congenital amaurosis
    • Meckel-Gruber syndrome
    • nephronophtisis
    • orofaciodigital syndrome
    • Senior–Løken syndrome
  • disorders with obesity, endocrine anomalies, and genital anomalies:
    • Alström syndrome
    • Bardet–Biedl syndrome
    • McKusick-Kaufman syndrome
  • disorders with chondrodysplasia:
    • Ellis van Creveld syndrome
    • Jeune asphyxiating thoracic dystrophy
    • Sensenbrenner syndrome (cranioectodermal dysplasia)
    • short ribs polydactyly syndrome
  • polycystic kidney syndromes:
    • autosomal dominant polycystic kidney disease
    • autosomal recessive polycystic kidney disease

Radiographic features

Cilopathies have a varied radiological appearance and some appear more commonly than others in radiological practice. For example, autosomal dominant polycystic kidney is a ciliopathy that may be occasionally encountered in most departments, while others such as Meckel-Gruber syndrome or short ribs polydactyly syndrome may only be encountered in specialist obstetrics imaging centers.

History and etymology

Cilium is Latin for eyelash.