With limited diffusion, there is a higher concentration of IgM, factor C1 of the complement cascade, and Langerhans cells. Any kind of inflammatory stimulus present in the peripheral cornea results in recruitment of neutrophil and activation of both classical and alternative pathways of immune response, namely the humoral and cell-mediated autoimmune responses. These responses will lead to the formation of antigen-specific antibodies to combat foreign antigens. However, antigen-antibody complexes formed may deposit in the vascular endothelium and activate complements leading to severe local inflammation. Under this circumstance, inflammatory cells, such as macrophages and neutrophils, enter the peripheral cornea. These inflammatory cells release enzymes protease and collagenases, causing potential disruption of the corneal stroma. The additional release of cytokines, for example, interleukin-1, from these cells further accelerates the process of stromal destruction. Moorens ulcer and relevant classification
Moorens ulcer is a common form of PUK. One classification of Moorens ulcer, based on the clinical presentation, includes bilateral indolent moorens ulcer, bilateral aggressive moorens ulcer and unilateral moorens ulcer. Unilateral moorens ulcer, meaning ulcer of one eye, mainly affects elderly above 60 years old. Rapid onset with redness and severe pain of the affected eye and either slow or extremely quick progression are some typical characteristics of unilateral moorens ulcer. Bilateral aggressive moorens ulcer is prevalent in Indian between age 14 to 40. The common presentation includes the appearance of lesions in one eye, followed by the development of lesions in another eye. Finally, bilateral indolent moorens ulcer is common in patients of at least 50-year-old.
The nose is prominent. The jaw can be small. The palate is narrow and grooved. There will be delay in fall of milk teeth. The permanent teeth can also be slow to appear. The permanent teeth are commonly irregular and teeth may be missing (hypodontia). The collar bones are often underdeveloped and malformed. The nails are flat, grooved, and dysplastic. High bone density, Acro-osteolysis and obtuse mandibular angle are the characteristic radiological findings of this disorder.Pycnodysostosis also causes problems that may become evident with time. Aside from the broken bones, the distal phalanges and the collar bone can undergo slow progressive deterioration. Vertebral defects may permit the spine to curve laterally resulting in scoliosis. The dental problems often require orthodontic care and cavities are common. Patients with PYCD are at a high risk of severe obstructive sleep apnea (OSA) due to upper airway obstructions. OSA must be managed to prevent long term pulmonary complications.Amongst infrequent complications, attention should be paid to maxillofacial anomalies. Snoring can be one of the presenting complaints and this needs early evaluation and management of obstructive sleep apnea if present to prevent long term pulmonary complications. Genetics
PYCD is a rare autosomal recessive disorder. The molecular basis of pycnodysostosis was elucidated in 1996 by Gelb and collaborators  and the disorder results from biallelic pathogenic mutation in CTSK gene (OMIM * 601105).