The easiest way to diagnose<unk>  is when pachydermia, finger clubbing and periostosis of the long bones are present. New bone formation under the periosteum can be detected by radiographs of long bones. In order diagnose<unk> , often other diseases must be excluded. For example, to exclude secondary hypertrophic osteoarthropathy, any signs of cardiovascular, pulmonary, hepatic, intestinal and mediastinal diseases must be absent. MRI and ultrasound also have characterictic findings. Skin biopsy is another way to diagnose<unk> . However, it is not a very specific method, because other diseases share the same skin alterations with<unk> , such as myxedema and hypothyroidism. In order to exclude these other diseases, hormonal studies are done. For example, thyrotropin and growth hormone levels should be examined to exclude thyroid acropachy and acromegaly. However, skin biopsy helps to diagnose<unk>  in patients without skin manifestations. When clubbing is observed, it is helpful to check whether acroosteolysis of distal phalanges of fingers is present. This is useful to diagnose<unk> , because the combination of clubbing and acroosteolysis is only found in<unk>  and Cheney’s syndrome. Biomarkers and mutation analysis Since elevated PGE2 levels are correlated with<unk> , urinary PGE2 can be a useful biomarker for this disease. Additionally, HPGD mutation analyses are relatively cheap and simple and may prove to be useful in early investigation in patients with unexplained clubbing or children presenting<unk> -like features. Early positive results can prevent expensive and longtime tests at identifying the pathology. For the follow-up of<unk>  disease activity, bone formation markers such as TAP, BAP, BGP, carbodyterminal propeptide of type I procallagen or NTX can play an important role. Other biomarkers that can be considered are IL-6 and receptor activator of NF-κB ligand (RANKL), which are associated with increased bone resorption in some patients. However, further investigation is needed to confirm this use of disease monitoring. PGE2 may also be raised in patients with lung cancer and finger clubbing. This may be related to raised levels of cyclooxygenase-2, an enzyme involved in the metabolism of prostaglandins. A similar association has been noted in cystic fibrosis. Classification<unk>  is one of the two types of hypertrophic osteoarthropathy. It represents approximately 5% of the total hypertrophic osteoarthropathy cases. The other form is secondary hypertrophic osteoarthropathy (SHO). SHO usually has an underlying disease (such as cardiopulmonary diseases, malignancies or paraneoplastic syndrome). Unlike SHO,<unk>  does not have an underlying disease or malignancy.<unk>  can be divided into three categories: * The complete form occurs in 40% of the cases and can involve all the symptoms but mainly pachydermia, periostosis and finger clubbing. This is also referred to as the full-blown phenotype. * The incomplete form occurs in 54% of the cases and is characterized by having mainly effect on the bones and thereby the skeletal changes. Its effect on the skin (causing for instance pachydermia) is very limited. * The fruste form occurs in only 6% of the cases and is the opposite of the incomplete form. Minor skeletal changes are found, and mostly cutaneous symptoms are observed with limited periostosis. The cause of these differentiating pathologies is still unknown.
Pachydermoperiostosis
Acromegaly
Craniosynostosis
Melorheostosis
Buccal exostosis
Subungual exostosis
Achondroplasia
Pseudoachondroplasia