Angioid Streaks : More Information

Link to Angioid Streaks Pnemonic

In 1889, Doyne first described angioid streaks in a patient with retinal hemorrhages secondary to trauma. Later in 1892, Knapp named them angioid streaks because of their resemblance to blood vessels. Angioid streaks result from pathological changes at the level of the Bruch membrane, which was confirmed histologically in the late 1930s.

Controversy about the pathophysiology of angioid streaks exists. In some diseases, including pseudoxanthoma elasticum (PXE) and Paget disease, the Bruch membrane may become calcified and brittle with subsequent development of cracks. However, cytoimmunochemistry and x-ray analysis had shown that the earliest abnormality in PXE was abnormal accumulation and metabolism of polyanions (ie, glycosaminoglycans, glycoproteins) within the Bruch membrane.

The lines of force within the eye resulting from the pull of intrinsic and extrinsic ocular muscles on the relatively fixed site of the optic nerve have been studied. Those lines of forces had the same configuration as the peripapillary interlacement and radial extensions of angioid streaks. Such forces acting on the Bruch membrane undoubtedly account for the configuration of the breaks. However, in sickle cell disease, Bruch membrane calcification is not a common part of the pathology.

It is believed that the pathology may be a combination of diffuse elastic degeneration of the Bruch membrane, iron deposition in elastic fibers from hemolysis with secondary mineralization, and impairment of nutrition because of sickling, stasis, and small vessel occlusion. Klien proposed a dual mechanism as a cause of these cracks in general, as follows: a primary abnormality of fibers of the Bruch membrane, and an increase in availability of metal salts or a tendency for their deposition, resulting in a secondary brittleness of the membranes.

Moderate-to-severe central visual loss is mainly related to foveal involvement with a dehiscence of the underlying Bruch membrane or a neovascular membrane formation under the retina. Choroidal neovascularization (CNV) is the major cause of vision loss and affects 70-86% of patients with angioid streaks.

History

Visual acuity is normal unless a leakage, bleeding, or Bruch membrane dehiscence involves the central macula. Distorted central vision (metamorphopsia) and micropsia can be early signs of macular involvement.

Physical

Ophthalmoscopic findings are as follows:

• At times, angioid streaks can be difficult to identify unless a careful examination of the posterior pole is performed.
• Angioid streaks usually present as linear gray or dark red lines with irregular serrated edges lying beneath normal retinal blood vessels. The streaks intercommunicate in a ringlike fashion around the optic disc in 27% of cases and radiate outward in a tapering fashion from the peripapillary area in 73% of patients. The streaks run a convoluted course and tend to terminate abruptly. Angioid streaks usually do not extend past the equator.
• Associated findings in patients with angioid streaks are as follows:
  • Peau d'orange or leopard skin spotting, consisting of speckled yellowish mottling of the posterior pole mostly apparent in the temporal macula. This finding may antedate the appearance of angioid streaks. It is seen more frequently in patients with PXE and is caused by alterations at the level of the Bruch membrane as demonstrated by the diffuse pattern of hyperfluorescence on indocyanine green angiography (ICGA).
  • Peripapillary chorioretinal atrophy, focal peripheral chorioretinal scars (salmon spots), and reticular pigment dystrophy of the macula may be present at the time of diagnosis.
  • Optic nerve head drusen (hyaline bodies) may antedate the appearance of angioid streaks, and they may be the earliest clinical manifestations of PXE. As many as 25% of patients with angioid streaks have clinical or echographic evidence of disk drusen. These hyaline bodies were associated with neovascularization in the peripapillary area, and, in some patients, they were associated with acute visual loss due to the pressure effect on the optic nerve head.
  • Crystalline bodies typically are seen in the midperipheral fundus or inferior to the optic nerve. They are multiple, round, small, and subretinal lesions. Usually, these crystalline bodies cause some atrophy of the retinal pigment epithelium (RPE).
  • Optic atrophy may be seen in patients with Paget disease of the bone. It cannot be explained solely on the basis of bony compression.
• Severe visual impairment is caused by one of the following conditions in 70% of cases:
  • CNV with subsequent serous and hemorrhagic detachment of the fovea (most serious complication)
  • Choroidal rupture secondary to trivial trauma with secondary hemorrhage involving the fovea
  • Foveal involvement by a streak with damage to RPE and choriocapillaris (may result in permanent loss of central visual acuity)

Causes

• Idiopathic: In 50% of patients with angioid streaks, no associated systemic disease is present.
• Systemic association
  • PXE is an uncommon inherited disorder of connective tissue. It has generalized effects on the elastin fibrils in the dermis, arterial walls, heart, gastrointestinal (GI) tract, and Bruch membrane, resulting in mineralization and deposition of phosphorus. The 4 types of inheritance of PXE include 2 of which are autosomal dominant and 2 of which are autosomal recessive. It is the most common systemic disorder associated with angioid streaks. Diagnosing PXE is important because 85% of patients develop ocular involvement, usually after the second decade of life. The combination of PXE and ocular involvement is referred to as Grönblad-Strandberg syndrome.
  • Histologically, degenerative changes and calcifications of the elastic tissues in the skin and arteries are present. The following systemic findings may help the ophthalmologist to confirm the diagnosis of angioid streaks secondary to PXE, as well as to take care of complications.
  • Dermatologic findings include yellow papules, "chicken skin" arranged in a linear or reticulate pattern, in plaques, over the side of the neck, antecubital fossae, axillae, groin, and paraumbilical area.
  • Cardiovascular manifestations include accelerated hypertension at an earlier age due to atherosclerosis, which may be related to renovascular disease, premature coronary artery disease, peripheral vascular disease, and mitral incompetence.
  • Some patients develop genitourinary bleeding as part of PXE.
  • Neurologic findings may include cerebrovascular accidents, intracranial aneurysms, and cerebral ischemia.
• Paget disease is a chronic, progressive, and in some cases inherited disease, characterized by bone deformity. It may be confined to a few bones, or in some patients, it represents a generalized abnormality that gives rise to enlargement of the skull, kyphoscoliosis, deafness, and deformities of long bones. However, angioid streaks occur in fewer than 2% of patients. Osteoclastic activity with an osteoblastic reaction occurs. Although the etiology is unknown, some clinicians believe it is related to a slow virus infection, measles, or respiratory syncytial virus. Both males and females are affected equally.
• Ehlers-Danlos syndrome is a rare autosomal dominant disorder of collagen resulting from a deficiency of hydroxylysine. Ocular findings include epicanthal folds, keratoconus, high myopia, retinal detachment, blue sclera, ectopia lentis, and angioid streaks. Systemic associations include the following:
  • Skin and musculoskeletal - Thin hyperplastic skin that heals poorly, hyperextensible joints that may predispose to recurrent falls, hydrarthrosis, and pseudotumor formation over elbows and knees
  • Cardiovascular disease consists of bleeding diathesis, dissecting aneurysms, spontaneous rupture of large blood vessels, and mitral prolapse.
  • Others - Diaphragmatic hernias and diverticulum of the GI and respiratory tracts
• Hemoglobinopathies that are occasionally associated with angioid streaks include the following:
  • Homozygous sickle cell disease (Hb-SS)
  • Sickle cell trait (Hb-AS)
  • Sickle cell thalassemia (Hb-thal)
  • Sickle cell hemoglobin (Hb-SC)
  • Hemoglobin H (Hb-H)
  • Homozygous B-thalassemia major
  • Intermedia
  • Minor and hereditary spherocytosis
• The frequency of angioid streaks increases with age; it is about 1.5% in younger patients and increases to 22% in older patients. Complications, such as macular degeneration and choroidal neovascular membranes, are uncommon in this subgroup of patients with angioid streaks. In general, choroidal neovascular membranes (CNVM) and serous detachments of the macula are less common in black patients.
• Other systemic diseases associated with angioid streaks include the following:
  • Abetalipoproteinemia
  • Acromegaly
  • Dwarfism
  • Diabetes mellitus
  • Hemochromatosis
  • Facial angiomatosis
  • Idiopathic thrombocytic purpura
  • Chronic familial hyperphosphatemia
  • Hypercalcinosis
  • Diffuse lipomatosis
  • Acquired hemolytic anemia
  • Myopia
  • Neurofibromatosis
  • Epilepsy
  • Senile elastosis
  • Sturge-Weber syndrome
  • Trauma
  • Tuberous sclerosis