INTRODUCTION Granulomatous inflammation is a distinctive ...

Sarcoidosis
Sarcoidosis is a granulomatous (mononuclear) inflammatory disease, systemic in scope, of
undetermined etiology. In 1877, the cutaneous aspects of the disease was first described, but
mistook them for gout. Caesar Boeck subsequently described several patients with similar skin
manifestations and called them "sarkoid," because of the resemblance of the histological features
to sarcoma. He emphasized the systemic nature of the disease. Heerfordt in 1909, in his
description of "uveoparotid fever," first reported neurological manifestations in the form of
cranial nerve palsies (Metwally, 2006-4).
Pathophysiology
The causes of sarcoidosis are not clear. The present evidence suggests that active sarcoidosis
results from an exaggerated cellular immune response to either foreign or self-antigens. An
alternative hypothesis says that sarcoidosis may be a clinical syndrome that includes a collection
of different diseases, each with a different etiology. Various infectious, allergic, chemical, drug,
and autoimmune causes have been suggested and dismissed for lack of conclusive evidence, and
some form of atypical mycobacteria is now suspected (American Thoracic Society, 1999).
T-helper cells proliferate, resulting in an exaggerated response. They undergo differentiation to a
Th1-type cell under the influence of interleukin-4 (IL-4) and co-stimulator CD28. The Th1 cell
induces IL-2 and interferon gamma (IFN-gamma) on the macrophages, followed by a cascade of
chemotactic factors that promote formation of granuloma. IFN-gamma increases the expression of
major histocompatibility class (MHC) class II on macrophages, and activated macrophages
receptors carry an Fc receptor of immunoglobulin G (IgG) which potentiates their phagocytosis
function. This results in tissue destruction and granuloma formation is thought to be a secondary
process (Moller, 2003).
The pathologic hallmark of sarcoidosis is the noncaseating epithelioid granuloma composed of
nodules of epithelioid histiocytes that are non-caseating (unlike TB). A mixed inflammatory
reaction commonly surrounds the granulomas. Langerhans type giant cells are common. Special
intracytoplasmic inclusions—stellate shapes called asteroid bodies—and also Schaumann bodies
(laminated basophilic calcifications) are found. A similar picture may appear in other diseases so
that eventually the diagnosis may become a matter of excluding an infectious agent( Jones et al.,
1999). In neurosarcoidosis, the granulomas in the CNS, consists of lymphocytes and mononuclear
phagocytes surrounding a noncaseating epithelioid cell granuloma (Metwally, 2006-5).
Epidemiology
Internationally, the incidence of sarcoid varies from 0.04 per 100,000 in Spain to 64 per 100,000 in
Sweden. In the US, the prevalence of sarcoid varies widely, but generally it is more common in
African Americans. In Asia it is extremely rare, being almost unknown in Chinese and Southeast
Asians. Data from Japan showed native Japanese to be affected (Hunninghake et al., 1999). Most
symptomatic patients are aged 20-40 years. Sarcoidosis also can be seen in children and elderly
persons.
Neurosarcoidosis
Involvement of the CNS is referred to as neurosarcoidosis. Neurosarcoidosis is an uncommon but
severe, sometimes life-threatening, manifestation of sarcoidosis. It generally occurs in 5-16% of
cases usually if the disease has had substantial systemic involvement and signs of active disease
(Lower et al., 1997 and James, 1998). However, strictly neurological forms are seen in fewer than
10% of patients (Bourahoui et al., 2004). Neurosarcoidosis carries a mortality rate of 10%, twice