Cleft lip and/or cleft palate as coexisting defects in selected rare diseases, with emphasis on dental abnormalities and speech problems: a narrative review of the literature

Introduction
Nowadays, 600 genetic syndromes are known with reported cleft palate or cleft lip, however, the etiology is not exactly known.

Objectives: This paper aims to review the medical literature to present the issue of cleft lip and cleft palate in selected rare diseases. The above-mentioned syndromes are due to extremely complex and heterogeneous etiology.

Material and methods
Using hand and electronic methods, the literature was searched for original papers, case studies, review papers, epidemiological databases, and book chapters, which focused on cleft lip and/or cleft palate and rare diseases. Publications were dated from 1999 to 2019. The majority of articles were in English, except some Polish papers. Key terms used in the search included speech therapy, dental manifestation, rare diseases, Hay-Wells syndrome, Smith-Lemli-Opitz syndrome, diastrophic dysplasia, Apert syndrome, and Kabuki syndrome. There were 49 references in total.

Results
Cleft palate and cleft lip are not the most common birth defects in human population, but are probably the most complicated conditions, which require an interdisciplinary approach of specialists from numerous medical fields. If a cleft palate occurs, patients are more likely to be exposed to rejection and non-acceptance by society.

Conclusions
This narrative review provides a description of five rare genetic diseases associated with cleft palate and/or cleft lip, with an emphasis on orofacial symptoms. Cleft palate and cleft lip conditions affect patients’ quality of life and require multidisciplinary treatment.