[Bone findings in psoriasis]

Osteoarthropathia psoriatica of one leg: a manifestation of somatic mosaicism?

A psoriatic osteoarthropathy localized in the left quadrant of a male patient is described. Diagnosis was made on the basis of bone scintigraphy (specific distribution pattern) and histological evaluation of a bone biopsy. There is no indication of psoriasis in the patient's family. Nor is there an association to psoriasis-typical HLA markers. Psoriasis of the skin has not been found. Environmental factors, including a Köbner phenomenon on the skeleton resulting from a trauma 13 years ago (hallux rigidus operation), are discussed in connection with this manifestation. The genetic aspects of this unusual localization are considered.

Studies on psoriatic osteopathy

To demonstrate an as yet merely postulated generalized osteopathy in psoriatics, the serum calcium level, the alkaline phosphatase in the serum and the urinary excretion of hydroxyproline were evaluated in 24 patients with Ps and 24 patients with PA. Moreover, the bone bioptates from 25 patients with PA and 10 patients with Ps were examined histologically and measured morphometrically. The investigations provide evidence for the existence of a generalized "latent" osteopathy in terms of an elevated bone turnover rate without loss of bone volume (high turnover remodelling) in both patients with PA as well as those with Ps without arthritis. As a pathogenetically essential factor shared by dermatosis and "osteopathy", latent vitamin D deficiency and/or D hormone resistance is discussed.

Extra-articular processes in osteoarthropathia psoriatica

1. Osteo-articular manifestations in the context of osteoarthropathia psoriatica are characterized by two completely different processes. 2. The intra-capsular synovitis does not differ qualitatively in respect to twelve morphological characteristics from that of rheumatoid arthritis. Only RA-necroses never occur in psoriatic arthritis. 3. The extra-capsular process occurs at the compact as well as the spongy bone of the phalanges. The process shows no sign of a previous or current inflammation or of osteoclast activity. It is characterized by a focal loss of proteoglycan interstitial substance and the exposure of the collagen fiber matrix. 4. This focal proteoglycan loss sets off a process which takes place in four phases: a) Loss of proteoglycan interstitial substance and exposure of the preserved collagen fiber matrix of the bone. b) Deposition of osteoblast chains to the area of the exposed bone and formation of osteoid within the old collagen fiber framework. c) Remodelling of bone defects through filling in of the preserved collagen fiber matrix with newly formed woven bone. d) Reconstruction of this bone into lamellar bone, whereby excessive bone structure ("protuberances") may develop, but final balance of bone remains negative. 5. The described process, which begins with proteoglycan loss, is considered as an enzymatic disturbance, which is causatively connected to the skin process. Scintigraphic examinations indicate that this extra-articular process in the bone, in contrast to arthritis, in part clinically unobserved, is to a high percentage connected to the skin process and is, therefore, probably an integral part of psoriatic disease.