Additionally, they have not been shown to support Merkel-cell polyoma virus infection, which is believed to drive oncogenesis in approximately 80% of MCC.Instead, it has been proposed the MCC may originate from a Merkel cell precursor, at which point it gains features similar to those of Merkel cells. One such precursor is the human fibroblast. Evidence for a fibroblast precursor includes its location in the dermis, which is thought to be the primary site of origin for MCC. Additionally, in vitro experiments have demonstrated that fibroblasts not only support Merkel cell polyomavirus (MCV) infection but can be induced into having a MCC phenotype by the expression of viral proteins.However, others have argued that MCC likely derives from an epithelial precursor cell due to its frequent presence in mixed tumors including epithelial neoplasms such as squamous cell carcinoma. While epithelial cells are not typically found in the dermis, hair follicles include epithelial cells that have been shown to have oncogenic potential, and have therefore been proposed as a possible site for a MCC precursor.Finally, the presence of B-cell surface markers on MCC in addition to the high correlation between MCC and B-cell lymphomatous cancers have also led to suggestions that MCC may share a progenitor with B-cells. Because of the differences in physiology and prognosis between MCV+ and MCV- MCC (see below), however, some have suggested that these two subtypes of MCC may actually derive from different progenitor cells.Several factors are involved in the pathophysiology of MCC, including MCV, ultraviolet radiation (UV) exposure, and weakened immune function.
Heart-hand syndrome, Spanish type, also known as heart-hand syndrome type 3 or III, is a very rare genetic disorder which is characterized by heart, hand, and sometimes feet abnormalities. It is a type of heart-hand syndrome, a class of genetic disorders characterized by cardiac malformations and hand malformations. Only one family with the disorder has been reported in medical literature. Description
People with this disorder have symptoms that affect the heart, hands and feet. These include:

Heart
Sick sinus
Bundle branch block

Hands
Brachydactyly which resembles brachydactyly type C
Abnormal development of the middle phalanges of the fingers
Accessory ossicle on the proximal phalange of the index finger. Feet
Subtle feet anomalies such as syndactyly

Etimology
This condition was first discovered by Ruiz de la Fuente et al., when they described a 3-generation family from Spain with the symptoms mentioned above. The cardiac defects varied between family members; 3 members had intraventicular conduction defects and 1 had a sick sinus. In this family, the 2nd and 5th fingers were the most severely affected out of all the fingers. Autosomal dominant inheritance was suspected. == References ==