Primary Ciliary Dyskinesia (PCD) is a rare genetic disorder, characterized by abnormal function and/or abnormal ciliary structure.

PCD has an estimated prevalence in Italy of 1.1 per 10.000 inhabitants (1).

Etiopathogenesis:

The function of cilia of epithelial mucosal cells is to transport the mucus layer, produced by mucosal glands and muciparous cells.

In PCD an altered function of these cilia occurs, with resulting deficiency in mucociliary clearance system. In the upper and lower airways the defective cilia function leads to frequent infections promoted by mucus stagnation, with the consequent development of chronic rhino-sinusitis, otitis media and bronchiectasis (2, 3).

Symptoms:

In infants the initial symptoms are characterized by stuffy nose (more common in the early months of life), progressive hearing loss due to recurrent ear infections, mucopurulent rhinosinusitis, recurrent bronchitis and cough, with or without wheezing, and febrile episodes. The disease comes into adulthood with bronchiectasis and progressive destruction of the lung, which can require lung transplantation. The destruction of the tympanic membrane in response to recurrent otitis media can lead to hearing loss in adults. PCD may be also associated with sub fertility in both men and women. In other cases it is associated with abnormality in kidney, heart and eye. In 40-50% of cases, mirror image organ arrangement (Kartagener Syndrome) and other forms of heterotaxy are present.

Genetics:

PCD is usually inherited in the autosomal recessive pattern. Mutations in DNAH5 or DNAI1 genes occur in 30% of the patients and are always associated with a structural defect of the cilia. Another candidate gene is DNAH11, in which mutations cause an impaired cilia movement pattern, without any visible defect in ultrastructure. As a result, molecular genetic examination has become a useful examination in PCD.

Diagnosis:

One of the main problems in the diagnosis of PCD is the initial absence of specific symptoms. For this reason in most patients proper diagnostic examinations are delayed (4). In a recent review, the mean age at diagnosis in Italy was reported at 4.8 years (1).

The confirmation of the diagnosis is complicated, mainly because the cilia ultrastructure does not always correlate with function. A combination of structure and function analyses is necessary to ascertain the definitive diagnosis. An accurate diagnostic technique includes the direct visualization of frequency and pattern of cilia movement in native respiratory epithelium samples; this is obtained using a Nomarski Differential Interference-Contrast Microscope ( with high-speed video camera). However, great physician experience is required and secondary ciliary dysfunctions cannot be distinguished from the primary ones. Other useful tool for diagnosis is the measurement of nasal nitric oxide (NO), that results very low in these patients.

After these first procedures, it is mandatory to study c ilia ultrastructure by electron microscopy (E M ), evaluating also the cilia orientation . As the samples for E M examination need to be of high quality, they should be taken with nasal brushing , or brushing and/or mucosal biopsy of lower airways during fiberoptic bronchoscopy (FOB).

Bibliography:

1. Kuehni CE, Frischer T, Strippoli MP, Maurer E, Bush A, Nielsen KG, Escribano A, Lucas JS, Yiallouros P, Omran H, Eber E, O'Callaghan C, Snijders D, Barbato A; ERS Task Force on Primary Ciliary Dyskinesia in Children. Factors influencing age at diagnosis of primary ciliary dyskinesia in European children. Eur Respir J. 2010 Dec;36(6):1248-58.

2. Noone PG, Leigh MW, Sannuti A, Minnix SL, Carson JL, Hazucha M, Zariwala MA, Knowles MR. Primary ciliary dyskinesia: diagnostic and phenotypic features. Am J Respir Crit Care Med. 2004 Feb 15;169(4):459-67.

3. Barbato A, Frischer T, Kuehni CE, Snijders D, Azevedo I, Baktai G, Bartoloni L, Eber E, Escribano A, Haarman E, Hesselmar B, Hogg C, Jorissen M, Lucas J, Nielsen KG, O'Callaghan C, Omran H, Pohunek P, Strippoli MP, Bush A. Primary ciliary dyskinesia: a consensus statement on diagnostic and treatment approaches in children. Eur Respir J. 2009 Dec;34(6):1264-76.

4. Strippoli MP, Frischer T, Barbato A, Snijders D, Maurer E, Lucas JS, Eber E, Karadag B, Pohunek P, Zivkovic Z, Escribano A, O'Callaghan C, Bush A, Kuehni CE. Management of primary ciliary dyskinesia in European children: recommendations and clinical practice. Eur Respir J. 2012 Jan 26. [Epub ahead of print]